What was the primary mode of smallpox transmission? Implications for biodefense

Clade Ib: a new emerging threat in the Mpox outbreak

Monkeypox, a zoonotic virus in the Orthopoxvirus genus, has drawn global attention for its impact on public health. In the current Mpox outbreak, a novel clade, Ib, has emerged as a significant and potentially fatal threat. This review examines the dynamics of MPXV transmission, person-to-person spread, and infection mechanisms, highlighting key risk factors. We explore the clinical features of Mpox, focusing on symptomology, illness duration, and the distinguishing characteristics of clade Ib compared to other clades. A critical analysis addresses diagnostic techniques and emphasizes the need for robust surveillance, particularly for clade Ib detection. We review recent prevention and treatment strategies, including antiviral drugs and vaccines, with a focus on clade Ib containment. The conclusion underscores the urgency of global collaboration to prevent and prepare for emerging threats like clade Ib and identifies crucial research paths and knowledge gaps. This review offers a comprehensive overview of clade Ib, covering its emergence, genetic traits, epidemiological impact, transmission patterns, clinical features, the role of Artificial Intelligence (AI) in outbreak management, detection challenges, and implications for public health response.

In silico prediction of pathogen's pandemic potential using the viral trait assessment for pandemics (ViTAP) model

Our world is ever evolving and interconnected, creating constant opportunities for disease outbreaks and pandemics to occur, making pandemic preparedness and pathogen management crucial for global health security. Early pathogen identification and intervention play a key role in mitigating the impacts of disease outbreaks. In this perspective, we present the Viral Trait Assessment for Pandemics (ViTAP) model to aid in the early identification of high-risk viruses that have pandemic potential, which incorporates lessons from past pandemics, including which key viral characteristics are important such as genetic makeup, transmission modes, mutation rates, and symptom severity. This model serves as the foundation for the development of powerful, quantitative tools for the early prediction of pandemic pathogens. The use of such a tool, in conjunction with other pandemic preparedness measures, can allow for early intervention and containment of the virus. This proactive approach could enable timely interventions, guiding public health responses, and resource allocation to prevent widespread outbreaks and mitigate the impact of emerging pathogens.

Symptom propagation in respiratory pathogens of public health concern: a review of the evidence

Symptom propagation occurs when the symptom set an individual experiences is correlated with the symptom set of the individual who infected them. Symptom propagation may dramatically affect epidemiological outcomes, potentially causing clusters of severe disease. Conversely, it could result in chains of mild infection, generating widespread immunity with minimal cost to public health. Despite accumulating evidence that symptom propagation occurs for many respiratory pathogens, the underlying mechanisms are not well understood. Here, we conducted a scoping literature review for 14 respiratory pathogens to ascertain the extent of evidence for symptom propagation by two mechanisms: dose-severity relationships and route-severity relationships. We identify considerable heterogeneity between pathogens in the relative importance of the two mechanisms, highlighting the importance of pathogen-specific investigations. For almost all pathogens, including influenza and SARS-CoV-2, we found support for at least one of the two mechanisms. For some pathogens, including influenza, we found convincing evidence that both mechanisms contribute to symptom propagation. Furthermore, infectious disease models traditionally do not include symptom propagation. We summarize the present state of modelling advancements to address the methodological gap. We then investigate a simplified disease outbreak scenario, finding that under strong symptom propagation, isolating mildly infected individuals can have negative epidemiological implications.

Genomic and transcriptomic analysis of the recent Mpox outbreak

The Mpox (formerly named Monkeypox) virus is the etiological cause of a recent multi-country outbreak, with thousands of distinct cases detected outside the endemic areas of Africa as of December 2023. In this article, we analyze the sequences of full genomes of Mpox virus from Europe and compare them with all available Mpox sequences of historical relevance, annotated by year and geographic origin, as well as related Cowpox and Variola (smallpox) virus sequences. Our results show that the recent outbreak is most likely originating from the West African clade of Mpox, with >99 % sequence identity with sequences derived from historical and recent cases, dating from 1971 to 2017. We analyze specific mutations occurring in viral proteins between the current outbreak, previous Mpox and Cowpox sequences, and the historical Variola virus. Genome-wide sequence analysis of the recent outbreak and other Mpox/Cowpox/Variola viruses shows a very high conservation, with 97.9 % (protein-based) and 97.8 % (nucleotide-based) sequence identity. We identified significant correlation in human transcriptional responses as well, with a conserved immune pathway response induced in human cell cultures by the three families of Pox virus. The similarities identified between the major strains of Pox viruses, as well as within the Mpox clades, both at the genomic and transcriptomic levels, provide a molecular basis for the observed efficacy of Variola vaccines in other Poxviruses.

Poxviridae Pneumonia

Poxviridae family includes several viruses that infecting humans usually causes skin lesions only, but in some cases their clinical course is complicated by viral pneumonia (with or without bacterial superinfections). Historically variola virus has been the poxviridae most frequently associated with the development of pneumonia with many large outbreaks worldwide before its eradication in 1980. It is still considered a biological threat for its potential in biological warfare and bioterrorism. Smallpox pneumonia can be severe with the onset of acute respiratory distress syndrome (ARDS) and death. Vaccinia virus, used for vaccination against smallpox exceptionally, in immunocompromised patients, can induce generalized (with also lung involvement) severe disease after vaccination. MPXV virus occasionally can cause pneumonia particularly in immunocompromised patients. The pathophysiology of poxviridae pneumonia is still an area of active research; however, in animal models these viruses can cause both direct damage to the lower airways epithelium and a hyperinflammatory syndrome, like a cytokine storm. Multiple mechanisms of immune evasion have also been described. The treatment of poxviridae pneumonia is mainly based on careful supportive care. Despite the absence of randomized clinical trials in patients with poxviridae pneumonia there are antiviral drugs, such as tecovirimat, cidofovir and brincidofovir, FDA-approved for use in smallpox and also available under an expanded access protocol for treatment of MPXV. There are 2 (replication-deficient modified vaccinia Ankara and replication-competent vaccinia virus) smallpox vaccines FDA-approved with the first one also approved for prevention of MPXV in adults that are at high risk of infection.

Poxviruses in Children

The family Poxviridae is a large family of viruses with a ubiquitous distribution, subdivided into two subfamilies: Chordopoxvirinae (poxviruses of vertebrates) and Entomopoxvirinae (poxviruses of insects). Only three species from the first subfamily, Orthopoxvirus (OPV), Molluscipoxvirus and Parapoxvirus, can infect the human being. In the paediatric population, viruses belonging to the first two subfamilies have the greatest importance. Following the eradication of smallpox in 1980, vaccination of the general population was discontinued after careful consideration of the risks and benefits. However, nearly all children and most of the world's population had little to no protection against OPV. The aim of this chapter is to review the current evidence on the aetiology, clinical manifestations, diagnosis and management of Poxviridae infections in children.

Emergence of mpox in the post-smallpox era-a narrative review on mpox epidemiology

BACKGROUND

The 2022 mpox outbreak drew global attention to this neglected pathogen. While most of the world was taken by surprise, some countries have seen this pathogen emerge and become endemic several decades prior to this epidemic.

OBJECTIVES

This narrative review provides an overview of mpox epidemiology since its discovery through the 2022 global outbreak.

SOURCES

We searched PubMed for relevant literature about mpox epidemiology and transmission through 28 February 2023.

CONTENT

The emergence of human mpox is intertwined with the eradication of smallpox and the cessation of the global smallpox vaccination campaign. The first human clade I and II monkeypox virus (MPXV) infections were reported as zoonoses in Central and West Africa, respectively, around 1970 with sporadic infections reported throughout the rest of the decade. Over the next five decades, Clade I MPXV was more common and caused outbreaks of increasing size and frequency, mainly in the Democratic Republic of the Congo. Clade II MPXV was rarely observed, until its re-emergence and ongoing transmission in Nigeria, since 2017. Both clades showed a shift from zoonotic to human-to-human transmission, with potential transmission through sexual contact being observed in Nigeria. In 2022, clade II MPXV caused a large human outbreak which to date has caused over 86,000 cases in 110 countries, with strong evidence of transmission during sexual contact. By February 2023, the global epidemic has waned in most countries, but endemic regions continue to suffer from mpox.

IMPLICATIONS

The changing epidemiology of mpox demonstrates how neglected zoonosis turned into a global health threat within a few decades. Thus, mpox pathophysiology and transmission dynamics need to be further investigated, and preventive and therapeutic interventions need to be evaluated. Outbreak response systems need to be strengthened and sustained in endemic regions to reduce the global threat of mpox.

A Review of the Past, Present, and Future of the Monkeypox Virus: Challenges, Opportunities, and Lessons from COVID-19 for Global Health Security

Monkeypox, a rare but significant zoonotic and orthopoxviral disease, has garnered increasing attention due to its potential for human-to-human transmission and its recent resurgence in multiple countries throughout Europe, North America, and Oceania. The disease has emerged as a novel threat to the global health systems that are still striving to recover from the major shocks of the COVID-19 pandemic. The unusual manifestation of the illness highlights a substantial knowledge deficit and necessitates the immediate development of a public health action strategy, considering the epidemiological differences observed in the ongoing outbreak and the appearance of cases in non-endemic nations. This literature review aims to synthesize existing knowledge on monkeypox, encompassing its historical context, etiology, epidemiology, surveillance, prevention, transmission, clinical presentation, diagnosis, treatments, and recent outbreak. Particular attention is given to both advances and gaps in our understanding of monkeypox, and we point toward future directions for research and intervention efforts as pertains to vaccine development and distribution. Lastly, we will also review the recent outbreak through a sociopolitical lens as relates to decision-making strategies, especially given the lessons learned from COVID-19.

Detection of Asymptomatic Mpox Carriers among High-Ri Men Who Have Sex with Men: A Prospective Analysis

Mpox is traditionally considered a zoonotic disease with endemic circulation in Africa, but the 2022-2023 outbreak reached an unprecedented high number of cases in non-endemic countries, so that it was declared a public health emergency of international concern. The reasons for this extensive global spread, characterized by sexual transmission amongst men who have sex with men (MSM), have not been fully clarified. The existence of asymptomatic carriers with viable viral shedding might be an explanation and is under-debated after retrospective studies suggested that infection without symptoms might have a prevalence of 6.5%. We aimed to prospectively assess the presence of mpox infection in asymptomatic high-risk MSM using HIV pre-exposure prophylaxis and living with HIV. We selected individuals with no signs of active infection nor suggestive symptoms in the previous 21 days. Eligible individuals collected oral and anal swabs to undergo point-of-care testing for mpox and completed a 21-days follow-up. Seventy-two individuals were enrolled, and none tested positive for mpox infection nor developed symptoms during follow-up. We selected a high-risk population with a significant history of sexual exposure, but we failed to detect any asymptomatic infection. This observation might have important consequences in terms of contact management and epidemic control.

Mechanisms, Techniques and Devices of Airborne Virus Detection: A Review

Airborne viruses, such as COVID-19, cause pandemics all over the world. Virus-containing particles produced by infected individuals are suspended in the air for extended periods, actually resulting in viral aerosols and the spread of infectious diseases. Aerosol collection and detection devices are essential for limiting the spread of airborne virus diseases. This review provides an overview of the primary mechanisms and enhancement techniques for collecting and detecting airborne viruses. Indoor virus detection strategies for scenarios with varying ventilations are also summarized based on the excellent performance of existing advanced comprehensive devices. This review provides guidance for the development of future aerosol detection devices and aids in the control of airborne transmission diseases, such as COVID-19, influenza and other airborne transmission viruses.

[The role of the pulmonologist in an armed conflict]

INTRODUCTION

Recent news points to the eventuality of an armed conflict on the national territory.

STATE OF THE ART

In this situation, pulmonologists will in all likelihood have a major role to assume in caring for the injured, especially insofar as chest damage is a major cause of patient death.

PERSPECTIVES

The main injuries that pulmonologists may be called upon to treat stem not only from explosions, but also from chemical, biological and nuclear hazards. In this article, relevant organizational and pedagogical aspects are addressed. Since exhaustiveness on this subject is unattainable, we are proposing training on specific subjects for interested practitioners.

CONCLUSION

The resilience of the French health system in a situation of armed conflict depends on the active participation of all concerned parties. With this in mind, it is of prime importance that the pneumological community be sensitized to the potential predictable severity of war-related injuries.

Monitoring monkeypox virus in saliva and air samples in Spain: a cross-sectional study

BACKGROUND

The transmission of monkeypox virus occurs through direct contact, but transmission through saliva or exhaled droplets and aerosols has not yet been investigated. We aimed to assess the presence of monkeypox virus DNA and infectious virus in saliva samples and droplets and aerosols exhaled from patients infected with monkeypox virus.

METHODS

We did a cross-sectional study in patients with monkeypox confirmed by PCR who attended two health centres in Madrid, Spain. For each patient, we collected samples of saliva, exhaled droplets within a mask, and aerosols captured by air filtration through newly developed nanofiber filters. We evaluated the presence of monkeypox virus in the samples by viral DNA detection by quantitative PCR (qPCR) and isolation of infectious viruses in cell cultures.

FINDINGS

Between May 18 and July 15, 2022, 44 patients with symptomatic monkeypox attended two health centres in Madrid and were included in the study. All were cisgender men, with a median age of 35·0 years (IQR 11·3). We identified high loads of monkeypox virus DNA by qPCR in 35 (85%) of 41 saliva samples. Infectious monkeypox virus was recovered from 22 (67%) of 33 saliva samples positive for monkeypox virus DNA. We also found a significant association between the number of affected cutaneous areas or general symptoms and the viral load present in saliva samples. Droplets exhaled from patients with monkeypox, detected inside a mask, contained monkeypox virus DNA in 32 (71%) of 45 samples, with two of the 32 positive samples showing the presence of the infectious virus. Monkeypox virus DNA in aerosols, collected from the medical consultation room, were detected in 27 (64%) of 42 samples, despite patients wearing an FFP2 mask during the visit. Infectious virus was not recovered from aerosol samples. High levels of monkeypox virus DNA were identified in aerosols collected from a hospital isolation room housing a patient with monkeypox.

INTERPRETATION

The identification of high viable monkeypox virus loads in saliva in most patients with monkeypox and the finding of monkeypox virus DNA in droplets and aerosols warrants further epidemiological studies to evaluate the potential relevance of the respiratory route of infection in the 2022 monkeypox virus outbreak.

FUNDING

EU, Consejo Superior de Investigaciones Científicas, and Ciberinfec.

Aerosol transmission of human pathogens: From miasmata to modern viral pandemics and their preservation potential in the Anthropocene record

Ongoing uncertainty over the relative importance of aerosol transmission of COVID-19 is in part rooted in the history of medical science and our understanding of how epidemic diseases can spread through human populations. Ancient Greek medical theory held that such illnesses are transmitted by airborne pathogenic emanations containing particulate matter ("miasmata"). Notable Roman and medieval scholars such as Varro, Ibn al-Khatib and Fracastoro developed these ideas, combining them with early germ theory and the concept of contagion. A widely held but vaguely defined belief in toxic miasmatic mists as a dominant causative agent in disease propagation was overtaken by the science of 19th century microbiology and epidemiology, especially in the study of cholera, which was proven to be mainly transmitted by contaminated water. Airborne disease transmission came to be viewed as burdened by a dubious historical reputation and difficult to demonstrate convincingly. A breakthrough came with the classic mid-20th century work of Wells, Riley and Mills who proved how expiratory aerosols (their "droplet nuclei") could transport still-infectious tuberculosis bacteria through ventilation systems. The topic of aerosol transmission of pathogenic respiratory diseases assumed a new dimension with the mid-late 20th century "Great Acceleration" of an increasingly hypermobile human population repeatedly infected by different strains of zoonotic viruses, and has taken centre stage this century in response to outbreaks of new respiratory infections that include coronaviruses. From a geoscience perspective, the consequences of pandemic-status diseases such as COVID-19, produced by viral pathogens utilising aerosols to infect a human population currently approaching 8 billion, are far-reaching and unprecedented. The obvious and sudden impacts on for example waste plastic production, water and air quality and atmospheric chemistry are accelerating human awareness of current environmental challenges. As such, the "anthropause" lockdown enforced by COVID-19 may come to be seen as a harbinger of change great enough to be preserved in the Anthropocene stratal record.

What were the historical reasons for the resistance to recognizing airborne transmission during the COVID-19 pandemic?

The question of whether SARS-CoV-2 is mainly transmitted by droplets or aerosols has been highly controversial. We sought to explain this controversy through a historical analysis of transmission research in other diseases. For most of human history, the dominant paradigm was that many diseases were carried by the air, often over long distances and in a phantasmagorical way. This miasmatic paradigm was challenged in the mid to late 19th century with the rise of germ theory, and as diseases such as cholera, puerperal fever, and malaria were found to actually transmit in other ways. Motivated by his views on the importance of contact/droplet infection, and the resistance he encountered from the remaining influence of miasma theory, prominent public health official Charles Chapin in 1910 helped initiate a successful paradigm shift, deeming airborne transmission most unlikely. This new paradigm became dominant. However, the lack of understanding of aerosols led to systematic errors in the interpretation of research evidence on transmission pathways. For the next five decades, airborne transmission was considered of negligible or minor importance for all major respiratory diseases, until a demonstration of airborne transmission of tuberculosis (which had been mistakenly thought to be transmitted by droplets) in 1962. The contact/droplet paradigm remained dominant, and only a few diseases were widely accepted as airborne before COVID-19: those that were clearly transmitted to people not in the same room. The acceleration of interdisciplinary research inspired by the COVID-19 pandemic has shown that airborne transmission is a major mode of transmission for this disease, and is likely to be significant for many respiratory infectious diseases.

Monkeypox: considerations for the understanding and containment of the current outbreak in non-endemic countries

The neglected and rare zoonotic disease caused by monkeypox virus (MPV) has recently spread widely, resulting in the largest known monkeypox outbreak outside of Africa, where it is endemic. MPV belongs to the Poxviridae family, genus Orthopoxvirus. At least two different clades have been identified, each having different fatality rates but recent cases are all phylogenetically related to the West African clade. MPV is transmitted directly by either person-to-person, -animal, or virus-contaminated fomite contact. The disease is often self-limited, and clinical symptoms include fever, skin lesions, and lymphadenopathies. At present, no deaths have been associated with the current outbreak. MPV DNA detection using molecular techniques is recommended for diagnosis. At least two approved drugs for antiviral therapy are available in the USA. Two different vaccines, including the vaccine used in the past for smallpox eradication and a new formulation more recently approved based on a live but non-replicating virus, are available that provide immunity to MPV. These and other clinical and public health considerations pertaining to the recent monkeypox outbreaks together with aspects of MPV biology are discussed in this article.

Modeling Clothing as a Vector for Transporting Airborne Particles and Pathogens across Indoor Microenvironments

Evidence suggests that human exposure to airborne particles and associated contaminants, including respiratory pathogens, can persist beyond a single microenvironment. By accumulating such contaminants from air, clothing may function as a transport vector and source of "secondary exposure". To investigate this function, a novel microenvironmental exposure modeling framework (ABICAM) was developed. This framework was applied to a para-occupational exposure scenario involving the deposition of viable SARS-CoV-2 in respiratory particles (0.5-20 μm) from a primary source onto clothing in a nonhealthcare setting and subsequent resuspension and secondary exposure in a car and home. Variability was assessed through Monte Carlo simulations. The total volume of infectious particles on the occupant's clothing immediately after work was 4800 μm3 (5th-95th percentiles: 870-32 000 μm3). This value was 61% (5-95%: 17-300%) of the occupant's primary inhalation exposure in the workplace while unmasked. By arrival at the occupant's home after a car commute, relatively rapid viral inactivation on cotton clothing had reduced the infectious volume on clothing by 80% (5-95%: 26-99%). Secondary inhalation exposure (after work) was low in the absence of close proximity and physical contact with contaminated clothing. In comparison, the average primary inhalation exposure in the workplace was higher by about 2-3 orders of magnitude. It remains theoretically possible that resuspension and physical contact with contaminated clothing can occasionally transmit SARS-CoV-2 between humans.

COVID-19: the case for aerosol transmission

The COVID-19 pandemic is the most severe pandemic caused by a respiratory virus since the 1918 influenza pandemic. As is the case with other respiratory viruses, three modes of transmission have been invoked: contact (direct and through fomites), large droplets and aerosols. This narrative review makes the case that aerosol transmission is an important mode for COVID-19, through reviewing studies about bioaerosol physiology, detection of infectious SARS-CoV-2 in exhaled bioaerosols, prolonged SARS-CoV-2 infectivity persistence in aerosols created in the laboratory, detection of SARS-CoV-2 in air samples, investigation of outbreaks with manifest involvement of aerosols, and animal model experiments. SARS-CoV-2 joins influenza A virus as a virus with proven pandemic capacity that can be spread by the aerosol route. This has profound implications for the control of the current pandemic and for future pandemic preparedness.

Indoor aerosol science aspects of SARS-CoV-2 transmission

Knowledge about person-to-person transmission of SARS-CoV-2 is reviewed, emphasizing three components: emission of virus-containing particles and drops from infectious persons; transport and fate of such emissions indoors; and inhalation of viral particles by susceptible persons. Emissions are usefully clustered into three groups: small particles (diameter 0.1-5 µm), large particles (5-100 µm), and ballistic drops (>100 µm). Speaking generates particles and drops across the size spectrum. Small particles are removed from indoor air at room scale by ventilation, filtration, and deposition; large particles mainly deposit onto indoor surfaces. Proximate exposure enhancements are associated with large particles with contributions from ballistic drops. Masking and social distancing are effective in mitigating transmission from proximate exposures. At room scale, masking, ventilation, and filtration can contribute to limit exposures. Important information gaps prevent a quantitative reconciliation of the high overall global spread of COVID-19 with known transmission pathways. Available information supports several findings with moderate-to-high confidence: transmission occurs predominantly indoors; inhalation of airborne particles (up to 50 µm in diameter) contributes substantially to viral spread; transmission occurs in near proximity and at room scale; speaking is a major source of airborne SARS-CoV-2 virus; and emissions can occur without strong illness symptoms.

Viral Load of SARS-CoV-2 in Respiratory Aerosols Emitted by COVID-19 Patients while Breathing, Talking, and Singing

Background

Multiple SARS-CoV-2 superspreading events suggest that aerosols play an important role in driving the COVID-19 pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5μm) and fine (≤5μm) respiratory aerosols produced when breathing, talking, and singing.

Methods

Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing.

Results

Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63–5,821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of the total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative.

Conclusions

Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging, and whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies.

Town population size and structuring into villages and households drive infectious disease risks in pre-healthcare Finland

Social life is often considered to cost in terms of increased parasite or pathogen risk. However, evidence for this in the wild remains equivocal, possibly because populations and social groups are often structured, which affects the local transmission and extinction of diseases. We test how the structuring of towns into villages and households influenced the risk of dying from three easily diagnosable infectious diseases-smallpox, pertussis and measles-using a novel dataset covering almost all of Finland in the pre-healthcare era (1800-1850). Consistent with previous results, the risk of dying from all three diseases increased with the local population size. However, the division of towns into a larger number of villages decreased the risk of dying from smallpox and to some extent of pertussis but it slightly increased the risk for measles. Dividing towns into a larger number of households increased the length of the epidemic for all three diseases and led to the expected slower spread of the infection. However, this could be seen only when local population sizes were small. Our results indicate that the effect of population structure on epidemics, disease or parasite risk varies between pathogens and population sizes, hence lowering the ability to generalize the consequences of epidemics in spatially structured populations, and mapping the costs of social life, via parasites and diseases.

Societal Impacts of Pandemics: Comparing COVID-19 With History to Focus Our Response

COVID-19 has disrupted everyday life worldwide and is the first disease event since the 1918 H1N1 Spanish influenza (flu) pandemic to demand an urgent global healthcare response. There has been much debate on whether the damage of COVID-19 is due predominantly to the pathogen itself or our response to it. We compare SARS-CoV-2 against three other major pandemics (1347 Black Death, 1520's new world smallpox outbreaks, and 1918 Spanish Flu pandemic) over the course of 700 years to unearth similarities and differences in pathogen, social and medical context, human response and behavior, and long-term social and economic impact that should be used to shape COVID-19 decision-making. We conclude that <100 years ago, pandemic disease events were still largely uncontrolled and unexplained. The extensive damage wreaked by historical pandemics on health, economy, and society was a function of pathogen characteristics and lack of public health resources. Though there remain many similarities in patterns of disease spread and response from 1300 onwards, the major risks posed by COVID-19 arise not from the pathogen, but from indirect effects of control measures on health and core societal activities. Our understanding of the epidemiology and effective treatment of this virus has rapidly improved and attention is shifting toward the identification of long-term control strategies that balance consideration of health in at risk populations, societal behavior, and economic impact. Policymakers should use lessons from previous pandemics to develop appropriate risk assessments and control plans for now-endemic COVID-19, and for future pandemics.

Epicutaneous immunization with modified vaccinia Ankara viral vectors generates superior T cell immunity against a respiratory viral challenge

Modified Vaccinia Ankara (MVA) was recently approved as a smallpox vaccine. Variola is transmitted by respiratory droplets and MVA immunization by skin scarification (s.s.) protected mice far more effectively against lethal respiratory challenge with vaccinia virus (VACV) than any other route of delivery, and at lower doses. Comparisons of s.s. with intradermal, subcutaneous, or intramuscular routes showed that MVA_OVA s.s.-generated T cells were both more abundant and transcriptionally unique. MVA_OVA s.s. produced greater numbers of lung Ova-specific CD8⁺ T_RM and was superior in protecting mice against lethal VACV_OVA respiratory challenge. Nearly as many lung T_RM were generated with MVA_OVA s.s. immunization compared to intra-tracheal immunization with MVA_OVA and both routes vaccination protected mice against lethal pulmonary challenge with VACV_OVA. Strikingly, MVA_OVA s.s.-generated effector T cells exhibited overlapping gene transcriptional profiles to those generated via intra-tracheal immunization. Overall, our data suggest that heterologous MVA vectors immunized via s.s. are uniquely well-suited as vaccine vectors for respiratory pathogens, which may be relevant to COVID-19. In addition, MVA delivered via s.s. could represent a more effective dose-sparing smallpox vaccine.

Influenza A (H3) illness and viral aerosol shedding from symptomatic naturally infected and experimentally infected cases

BACKGROUND

It has long been known that nasal inoculation with influenza A virus produces asymptomatic to febrile infections. Uncertainty persists about whether these infections are sufficiently similar to natural infections for studying human-to-human transmission.

METHODS

We compared influenza A viral aerosol shedding from volunteers nasally inoculated with A/Wisconsin/2005 (H3N2) and college community adults naturally infected with influenza A/H3N2 (2012-2013), selected for influenza-like illness with objectively measured fever or a positive Quidel QuickVue A&B test. Propensity scores were used to control for differences in symptom presentation observed between experimentally and naturally infected groups.

RESULTS

Eleven (28%) experimental and 71 (86%) natural cases shed into fine particle aerosols (P < .001). The geometric mean (geometric standard deviation) for viral positive fine aerosol samples from experimental and natural cases was 5.1E + 3 (4.72) and 3.9E + 4 (15.12) RNA copies/half hour, respectively. The 95th percentile shedding rate was 2.4 log10 greater for naturally infected cases (1.4E + 07 vs 7.4E + 04). Certain influenza-like illness-related symptoms were associated with viral aerosol shedding. The almost complete lack of symptom severity distributional overlap between groups did not support propensity score-adjusted shedding comparisons.

CONCLUSIONS

Due to selection bias, the natural and experimental infections had limited symptom severity distributional overlap precluding valid, propensity score-adjusted comparison. Relative to the symptomatic naturally infected cases, where high aerosol shedders were found, experimental cases did not produce high aerosol shedders. Studying the frequency of aerosol shedding at the highest observed levels in natural infections without selection on symptoms or fever would support helpful comparisons.

Minimal transmission in an influenza A (H3N2) human challenge-transmission model within a controlled exposure environment

Uncertainty about the importance of influenza transmission by airborne droplet nuclei generates controversy for infection control. Human challenge-transmission studies have been supported as the most promising approach to fill this knowledge gap. Healthy, seronegative volunteer ‘Donors’ (n = 52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2). ‘Recipients’ randomized to Intervention (IR, n = 40) or Control (CR, n = 35) groups were exposed to Donors for four days. IRs wore face shields and hand sanitized frequently to limit large droplet and contact transmission. One transmitted infection was confirmed by serology in a CR, yielding a secondary attack rate of 2.9% among CR, 0% in IR (p = 0.47 for group difference), and 1.3% overall, significantly less than 16% (p<0.001) expected based on a proof-of-concept study secondary attack rate and considering that there were twice as many Donors and days of exposure. The main difference between these studies was mechanical building ventilation in the follow-on study, suggesting a possible role for aerosols.

Understanding the relative importance of influenza modes of transmission informs strategic use of preventive measures to reduce influenza risk in high-risk settings such as hospitals and is important for pandemic preparedness. Given the increasing evidence from epidemiological modelling, exhaled viral aerosol, and aerobiological survival studies supporting a role for airborne transmission and the potential benefit of respirators (and other precautions designed to prevent inhalation of aerosols) versus surgical masks (mainly effective for reducing exposure to large droplets) to protect healthcare workers, more studies are needed to evaluate the extent of risk posed airborne versus contact and large droplet spray transmission modes. New human challenge-transmission studies should be carefully designed to overcome limitations encountered in the current study. The low secondary attack rate reported herein also suggests that the current challenge-transmission model may no longer be a more promising approach to resolving questions about transmission modes than community-based studies employing environmental monitoring and newer, state-of-the-art deep sequencing-based molecular epidemiological methods.

Study on the motion law of aerosols produced by human respiration under the action of thermal plume of different intensities

Predicting influence of human thermal plume on the diffusion of respiration-produced particles is an important issue for improving indoor air quality through eliminating infectious microbes efficiently. In this study, the Large Eddy Simulation was utilized to predict the effects of thermal plume of different intensities on particle diffusion. Three postures of the human body model and three room temperatures were considered. The results show that the convective heat transfer coefficient on the surface of the human body varies greatly with different postures. The coefficient is the largest when the model is in sitting posture, leading to the greatest heat transfer rate. Meanwhile, the thermal plume generated by bending the thigh increases the size of the facial thermal plume in horizon direction. The increase of the difference between indoor temperature and skin temperature causes an increase of the convective heat transfer of the manikin, leading to stronger airflow in front of the face. The thicker and faster the human thermal plume is, the more difficult it is penetrated by aerosols produced by nasal breathing, finally resulting in most particles distributed within 0.2 m thick under the roof.

An Analysis of the United States and United Kingdom Smallpox Epidemics (1901-5) - The Special Relationship that Tested Public Health Strategies for Disease Control

At the end of the nineteenth century, the northern port of Liverpool had become the second largest in the United Kingdom. Fast transatlantic steamers to Boston and other American ports exploited this route, increasing the risk of maritime disease epidemics. The 1901-3 epidemic in Liverpool was the last serious smallpox outbreak in Liverpool and was probably seeded from these maritime contacts, which introduced a milder form of the disease that was more difficult to trace because of its long incubation period and occurrence of undiagnosed cases. The characteristics of these epidemics in Boston and Liverpool are described and compared with outbreaks in New York, Glasgow and London between 1900 and 1903. Public health control strategies, notably medical inspection, quarantine and vaccination, differed between the two countries and in both settings were inconsistently applied, often for commercial reasons or due to public unpopularity. As a result, smaller smallpox epidemics spread out from Liverpool until 1905. This paper analyses factors that contributed to this last serious epidemic using the historical epidemiological data available at that time. Though imperfect, these early public health strategies paved the way for better prevention of imported maritime diseases.

Evidence of Long-Distance Aerial Convection of Variola Virus and Implications for Disease Control

Two distinct phenomena of airborne transmission of variola virus (smallpox) were described in the pre-eradication era-direct respiratory transmission, and a unique phenomenon of transmission over greater distances, referred to as "aerial convection". We conducted an analysis of data obtained from a systematic review following the PRISMA criteria, on the long-distance transmission of smallpox. Of 8179 studies screened, 22 studies of 17 outbreaks were identified-12 had conclusive evidence of aerial convection and five had partially conclusive evidence. Aerial convection was first documented in 1881 in England, when smallpox incidence had waned substantially following mass vaccination, making unusual transmissions noticeable. National policy at the time stipulated spatial separation of smallpox hospitals from other buildings and communities. The evidence supports the transmission of smallpox through aerial convection at distances ranging from 0.5 to 1 mile, and one instance of 15 km related to bioweapons testing. Other explanations are also possible, such as missed chains of transmission, fomites or secondary aerosolization from contaminated material such as bedding. The window of observation of aerial convection was within the 100 years prior to eradication. Aerial convection appears unique to the variola virus and is not considered in current hospital infection control protocols. Understanding potential aerial convection of variola should be an important consideration in planning for smallpox treatment facilities and protecting potential contacts and surrounding communities.

How Valid Are Assumptions About Re-emerging Smallpox? A Systematic Review of Parameters Used in Smallpox Mathematical Models

Background

Globally eradicated in 1980, smallpox is listed as a category A bioterrorism agent. If smallpox were to re-emerge, it may be due to an act of bioterrorism or a laboratory accident, and the impact is likely to be severe. Preparedness against smallpox is subject to more uncertainty than other infectious diseases because it is eradicated, there is uncertainty about population immunity, and the current global health workforce has no practical experience or living memory of smallpox. In the event of re-emergence of smallpox, mathematical modeling plays a crucial role in improving the evidence base to inform preparedness, mitigation, and response activities. However, the predictions of mathematical models about outbreak magnitude and impact depend critically on the assumptions and disease parameters used. We aimed to identify modeling studies that would be applicable to re-emerging smallpox and to evaluate consistency and the certainty of the evidence published about the key parameters used.

Methods

We conducted a systematic review using PRISMA criteria, of assumptions used in modeling studies on duration of latent, prodromal, and infectious period, as well as the choice of the basic reproduction number (R0) for re-emerging smallpox. We performed a literature search using PubMED, Scopus, Web of Science, and EMBASE and included peer-reviewed articles that focused on smallpox models, stated at least three of the aforementioned parameters and published in English.

Findings

A total of 42 studies were selected for inclusion. There was general agreement on the duration of latent and prodromal periods, being 11-12 d (88%) and 3 d (59%), respectively. The duration of the infectious period varied from 4 to 20 d. Most models assumed 16 d (19%), 12 d (16.7%), and 8.6 d (12%) of infectiousness. In 25/34 studies, R0 ranged between 3 and 5, generally lower than the R0 calculated from past outbreaks.

Discussion

Models of smallpox re-emergence also tend to use the same limited available historical data sources but assume a wide range of different estimates for key parameters. Models use very optimistic assumptions of decreased population immunity, despite high uncertainty about duration and magnitude of post-vaccination immunity. This review reveals a paradox. A substantial proportion of the modern population is unvaccinated, never exposed to boosting from wild-type smallpox, or immunocompromised; furthermore, vaccine-induced immunity wanes over time. Failure to consider these factors in a model will lead to underestimating the true impact of a re-emergent smallpox epidemic in the contemporary population.

Computational Comparison and Visualization of Viruses in the Perspective of Clinical Information

This paper addresses the visualization of complex information using multidimensional scaling (MDS). MDS is a technique adopted for processing data with multiple features scattered in high-dimensional spaces. For illustrating the proposed techniques, the case of viral diseases is considered. The study evaluates the characteristics of 21 viruses in the perspective of clinical information. Several new schemes are proposed for improving the visualization of the MDS charts. The results follow standard clinical practice, proving that the method represents a valuable tool to study a large number of viruses.

Recognition of aerosol transmission of infectious agents: a commentary

Although short-range large-droplet transmission is possible for most respiratory infectious agents, deciding on whether the same agent is also airborne has a potentially huge impact on the types (and costs) of infection control interventions that are required.The concept and definition of aerosols is also discussed, as is the concept of large droplet transmission, and airborne transmission which is meant by most authors to be synonymous with aerosol transmission, although some use the term to mean either large droplet or aerosol transmission.However, these terms are often used confusingly when discussing specific infection control interventions for individual pathogens that are accepted to be mostly transmitted by the airborne (aerosol) route (e.g. tuberculosis, measles and chickenpox). It is therefore important to clarify such terminology, where a particular intervention, like the type of personal protective equipment (PPE) to be used, is deemed adequate to intervene for this potential mode of transmission, i.e. at an N95 rather than surgical mask level requirement.With this in mind, this review considers the commonly used term of 'aerosol transmission' in the context of some infectious agents that are well-recognized to be transmissible via the airborne route. It also discusses other agents, like influenza virus, where the potential for airborne transmission is much more dependent on various host, viral and environmental factors, and where its potential for aerosol transmission may be underestimated.

Recognition of aerosol transmission of infectious agents: a commentary

Although short-range large-droplet transmission is possible for most respiratory infectious agents, deciding on whether the same agent is also airborne has a potentially huge impact on the types (and costs) of infection control interventions that are required.The concept and definition of aerosols is also discussed, as is the concept of large droplet transmission, and airborne transmission which is meant by most authors to be synonymous with aerosol transmission, although some use the term to mean either large droplet or aerosol transmission.However, these terms are often used confusingly when discussing specific infection control interventions for individual pathogens that are accepted to be mostly transmitted by the airborne (aerosol) route (e.g. tuberculosis, measles and chickenpox). It is therefore important to clarify such terminology, where a particular intervention, like the type of personal protective equipment (PPE) to be used, is deemed adequate to intervene for this potential mode of transmission, i.e. at an N95 rather than surgical mask level requirement.With this in mind, this review considers the commonly used term of 'aerosol transmission' in the context of some infectious agents that are well-recognized to be transmissible via the airborne route. It also discusses other agents, like influenza virus, where the potential for airborne transmission is much more dependent on various host, viral and environmental factors, and where its potential for aerosol transmission may be underestimated.

Characterization of the immune response elicited by the vaccinia virus L3 protein delivered as naked DNA

Poxviruses are complex dsDNA viruses with over 200 genes, many of them with unknown role in the stimulation of immune responses. Among these, the vaccinia virus (VACV) L3L ORF encodes an essential protein for the transcription of the VACV early genes. To the best of our knowledge, the immune response elicited by L3 has not been characterized. In this regard, our data describes a DNA L3-coding plasmid (pL3L) that stimulates both, humoral- and cell-mediated immune responses in a mouse model. Cell-mediated immune responses were measured by IFN-γ and IL-4 ELISPOT assays. We performed CD8⁺ cells depletion and flow cytometry analysis to account for the contribution of cytotoxic T lymphocytes in the IFN-γ production. Moreover, results from ELISPOT were confirmed by measuring the concentration of IL-4 and IFN-γ in supernatant of antigen-stimulated splenocytes by cytokine ELISA. Additionally, dominant antigenic regions of L3 protein were identified by epitope mapping analysis. Humoral immune responses were assessed by ELISA. Specifically, the production of total IgG, IgG1 (TH-2) and IgG2a (TH-1) were determined one week after the final immunization. Our ELISPOT data shows pL3L-immunized animals to produce significantly higher frequencies of IFN-γ Spot-Forming Cells (SFC) versus controls. IL-4 levels remained unchanged in all three groups, demonstrating the increase in antigen-specific IFN-γ releasing cells. Flow cytometry assay results showed that CD8⁺ T cells are a major contributor to the production of IFN-γ. Moreover, our formulation enhances the production of total IgG, predominantly IgG2a isotype. Immunization with pL3L promotes a robust cytotoxic immune response, crucial against viral pathogens. In addition, our vaccine candidate promotes an increase in IgG levels, especially IgG2a (TH-1 type). Our data encourages further studies of L3 as a novel antigen in vaccine development against poxviruses.

Assessment of a respiratory face mask for capturing air pollutants and pathogens including human influenza and rhinoviruses

Background

Prevention of infection with airborne pathogens and exposure to airborne particulates and aerosols (environmental pollutants and allergens) can be facilitated through use of disposable face masks. The effectiveness of such masks for excluding pathogens and pollutants is dependent on the intrinsic ability of the masks to resist penetration by airborne contaminants. This study evaluated the relative contributions of a mask, valve, and Micro Ventilator on aerosol filtration efficiency of a new N95 respiratory face mask.

Methods

The test mask was challenged, using standardized methods, with influenza A and rhinovirus type 14, bacteriophage ΦΧ174, Staphylococcus aureus (S. aureus), and model pollutants. The statistical significance of results obtained for different challenge microbial agents and for different mask configurations (masks with operational or nonoperational ventilation fans and masks with sealed Smart Valves) was assessed.

Results

The results demonstrate >99.7% efficiency of each test mask configuration for exclusion of influenza A virus, rhinovirus 14, and S. aureus and >99.3% efficiency for paraffin oil and sodium chloride (surrogates for PM_2.5). Statistically significant differences in effectiveness of the different mask configurations were not identified. The efficiencies of the masks for excluding smaller-size (i.e., rhinovirus and bacteriophage ΦΧ174) vs. larger-size microbial agents (influenza virus, S. aureus) were not significantly different.

Conclusions

The masks, with or without features intended for enhancing comfort, provide protection against both small- and large-size pathogens. Importantly, the mask appears to be highly efficient for filtration of pathogens, including influenza and rhinoviruses, as well as the fine particulates (PM_2.5) present in aerosols that represent a greater challenge for many types of dental and surgical masks. This renders this individual-use N95 respiratory mask an improvement over the former types of masks for protection against a variety of environmental contaminants including PM_2.5 and pathogens such as influenza and rhinoviruses.

Aerobiology: Experimental Considerations, Observations, and Future Tools

Understanding airborne survival and decay of microorganisms is important for a range of public health and biodefense applications, including epidemiological and risk analysis modeling. Techniques for experimental aerosol generation, retention in the aerosol phase, and sampling require careful consideration and understanding so that they are representative of the conditions the bioaerosol would experience in the environment. This review explores the current understanding of atmospheric transport in relation to advances and limitations of aerosol generation, maintenance in the aerosol phase, and sampling techniques. Potential tools for the future are examined at the interface between atmospheric chemistry, aerosol physics, and molecular microbiology where the heterogeneity and variability of aerosols can be explored at the single-droplet and single-microorganism levels within a bioaerosol. The review highlights the importance of method comparison and validation in bioaerosol research and the benefits that the application of novel techniques could bring to increasing the understanding of aerobiological phenomena in diverse research fields, particularly during the progression of atmospheric transport, where complex interdependent physicochemical and biological processes occur within bioaerosol particles.

Pandemic Risk Modelling

This chapter will explore the nature of communicable diseases, a brief history of pandemics, and will introduce the mathematical models used to evaluate the risk pandemics pose to human populations. Such modelling is used in a public health context, where modelling past and current events provides insight in how to respond most effectively to a new outbreak. It is also used in the context of risk mutualisation and transfer. As recently as 2013, a survey of 30,000 insurance executives placed global pandemic as the biggest extreme risk facing insurers (Towers Watson. 2013. Insurers Rate Global Pandemic as the Major Extreme Risk. 3 December). The chapter will introduce the principles used to model these events in the insurance industry and will conclude with a review of the way these models are applied in an unconventional risk transfer context.

Resistance of Aerosolized Bacterial Viruses to Four Germicidal Products

Viral diseases can spread through a variety of routes including aerosols. Yet, limited data are available on the efficacy of aerosolized chemicals to reduce viral loads in the air. Bacteriophages (phages) are often used as surrogates for hazardous viruses in aerosol studies because they are inexpensive, easy to handle, and safe for laboratory workers. Moreover, several of these bacterial viruses display physical characteristics similar to pathogenic human and animal viruses, like morphological size, type of nucleic acids, capsid morphology, and the presence of an envelope. In this study, the efficacy of four chemicals was evaluated on four airborne phages at two different relative humidity levels. Non-tailed bacteriophages MS2 (single-stranded RNA), ϕ6 (double-stranded RNA, enveloped), PR772 (double-stranded DNA), and ϕX174 (single-stranded DNA) were first aerosolized in a 55L rotative environmental chamber at 19°C with 25% and 50% relative humidity. Then, hydrogen peroxide, Eugenol (phenylpropene used in commercial perfumes and flavorings), Mist® (automobile disinfectant containing Triethylene glycol), and Pledge® (multisurface disinfectant containing Isopropanol, n-Alkyl Dimethyl Benzyl Amonium Chlorides, and n-Alkyl Dimethyl Ethylbenzyl Ammonium Chloride) were nebulized with the phages using a separate nebulizer. Aerosols were maintained in suspension during 10 minutes, 1 hour, and 2 hours. Viral aerosols were sampled using an SKC BioSampler and samples were analyzed using qPCR and plaque assays. The resistance levels of the four phages varied depending on the relative humidity (RH) and germicidal products tested. Phage MS2 was the most stable airborne virus under the environmental conditions tested while phage PR772 was the least stable. Pledge® and Eugenol reduced the infectivity of all airborne phages tested. At 25% RH, Pledge® and Eugenol were more effective at reducing infectivity of RNA phages ϕ6 and MS2. At 50% RH, Pledge® was the most effective agent against phage MS2. These findings illustrate that various airborne viruses should be tested to demonstrate the effectiveness of germicidal treatments. This research also provides a set of parameters for testing germicidal products in large-scale settings to reduce the risk of virus transmission.

Drivers of airborne human-to-human pathogen transmission

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Chain of pathogen transmission between individual donor and recipient is modeled.

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Related pairs of efficient and inefficient ‘airborne’ pathogens are contrasted.

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Drivers operate on tissue, individual, community, country, and global levels.

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Pandemic risk is heightened by pathogen evolution and changes in host interaction.

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Ultimate drivers include socio-economic developments and climate changes.

Airborne pathogens — either transmitted via aerosol or droplets — include a wide variety of highly infectious and dangerous microbes such as variola virus, measles virus, influenza A viruses, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Bordetella pertussis. Emerging zoonotic pathogens, for example, MERS coronavirus, avian influenza viruses, Coxiella, and Francisella, would have pandemic potential were they to acquire efficient human-to-human transmissibility. Here, we synthesize insights from microbiological, medical, social, and economic sciences to provide known mechanisms of aerosolized transmissibility and identify knowledge gaps that limit emergency preparedness plans. In particular, we propose a framework of drivers facilitating human-to-human transmission with the airspace between individuals as an intermediate stage. The model is expected to enhance identification and risk assessment of novel pathogens.

Non-invasive Imaging of Sendai Virus Infection in Pharmacologically Immunocompromised Mice: NK and T Cells, but not Neutrophils, Promote Viral Clearance after Therapy with Cyclophosphamide and Dexamethasone

In immunocompromised patients, parainfluenza virus (PIV) infections have an increased potential to spread to the lower respiratory tract (LRT), resulting in increased morbidity and mortality. Understanding the immunologic defects that facilitate viral spread to the LRT will help in developing better management protocols. In this study, we immunosuppressed mice with dexamethasone and/or cyclophosphamide then monitored the spread of viral infection into the LRT by using a noninvasive bioluminescence imaging system and a reporter Sendai virus (murine PIV type 1). Our results show that immunosuppression led to delayed viral clearance and increased viral loads in the lungs. After cessation of cyclophosphamide treatment, viral clearance occurred before the generation of Sendai-specific antibody responses and coincided with rebounds in neutrophils, T lymphocytes, and natural killer (NK) cells. Neutrophil suppression using anti-Ly6G antibody had no effect on infection clearance, NK-cell suppression using anti-NK antibody delayed clearance, and T-cell suppression using anti-CD3 antibody resulted in no clearance (chronic infection). Therapeutic use of hematopoietic growth factors G-CSF and GM-CSF had no effect on clearance of infection. In contrast, treatment with Sendai virus-specific polysera or a monoclonal antibody limited viral spread into the lungs and accelerated clearance. Overall, noninvasive bioluminescence was shown to be a useful tool to study respiratory viral progression, revealing roles for NK and T cells, but not neutrophils, in Sendai virus clearance after treatment with dexamethasone and cyclophosphamide. Virus-specific antibodies appear to have therapeutic potential.

Exposure of rhesus monkeys to cowpox virus Brighton Red by large-particle aerosol droplets results in an upper respiratory tract disease

We previously demonstrated that small-particle (0.5-3.0 µm) aerosol infection of rhesus monkeys (Macaca mulatta) with cowpox virus (CPXV)-Brighton Red (BR) results in fulminant respiratory tract disease characterized by severe lung parenchymal pathology but only limited systemic virus dissemination and limited classic epidermal pox-like lesion development (Johnson et al., 2015). Based on these results, and to further develop CPXV as an improved model of human smallpox, we evaluated a novel large-particle aerosol (7.0-9.0 µm) exposure of rhesus monkeys to CPXV-BR and monitored for respiratory tract disease by serial computed tomography (CT). As expected, the upper respiratory tract and large airways were the major sites of virus-induced pathology following large-particle aerosol exposure. Large-particle aerosol CPXV exposure of rhesus macaques resulted in severe upper airway and large airway pathology with limited systemic dissemination.

Multidimensional scaling analysis of virus diseases

BACKGROUND AND OBJECTIVE

Viruses are infectious agents that replicate inside organisms and reveal a plethora of distinct characteristics. Viral infections spread in many ways, but often have devastating consequences and represent a huge danger for public health. It is important to design statistical and computational techniques capable of handling the available data and highlighting the most important features.

METHODS

This paper reviews the quantitative and qualitative behaviour of 22 infectious diseases caused by viruses. The information is compared and visualized by means of the multidimensional scaling technique.

RESULTS

The results are robust to uncertainties in the data and revealed to be consistent with clinical practice.

CONCLUSIONS

The paper shows that the proposed methodology may represent a solid mathematical tool to tackle a larger number of virus and additional information about these infectious agents.

Defending against smallpox: a focus on vaccines

Smallpox has shaped human history, from the earliest human civilizations well into the 20th century. With high mortality rates, rapid transmission, and serious long-term effects on survivors, smallpox was a much-feared disease. The eradication of smallpox represents an unprecedented medical victory for the lasting benefit of human health and prosperity. Concerns remain, however, about the development and use of the smallpox virus as a biological weapon, which necessitates the need for continued vaccine development. Smallpox vaccine development is thus a much-reviewed topic of high interest. This review focuses on the current state of smallpox vaccines and their context in biodefense efforts.

Resistance of Aerosolized Bacterial Viruses to Relative Humidity and Temperature

The use of aerosolized bacteriophages as surrogates for hazardous viruses might simplify and accelerate the discovery of links between viral components and their persistence in the airborne state under diverse environmental conditions. In this study, four structurally distinct lytic phages, MS2 (single-stranded RNA [ssRNA]), ϕ6 (double-stranded RNA [dsRNA]), ϕX174 (single-stranded DNA [ssDNA]), and PR772 (double-stranded DNA [dsDNA]), were nebulized into a rotating chamber and exposed to various levels of relative humidity (RH) and temperature as well as to germicidal UV radiation. The aerosolized viral particles were allowed to remain airborne for up to 14 h before being sampled for analysis by plaque assays and quantitative PCRs. Phages ϕ6 and MS2 were the most resistant at low levels of relative humidity, while ϕX174 was more resistant at 80% RH. Phage ϕ6 lost its infectivity immediately after exposure to 30°C and 80% RH. The infectivity of all tested phages rapidly declined as a function of the exposure time to UVC radiation, phage MS2 being the most resistant. Taken altogether, our data indicate that these aerosolized phages behave differently under various environmental conditions and highlight the necessity of carefully selecting viral simulants in bioaerosol studies.

Aerosol-Transmitted Infections-a New Consideration for Public Health and Infection Control Teams

Since the emergence of the 2003 severe acute respiratory syndrome (SARS), the 2003 reemergence of avian A/H5N1, the emergence of the 2009 pandemic influenza A/H1N1, the 2012 emergence of Middle East respiratory syndrome (MERS), the 2013 emergence of avian A/H7N9 and the 2014 Ebola virus outbreaks, the potential for the aerosol transmission of infectious agents is now routinely considered in the investigation of any outbreak. Although many organisms have traditionally been considered to be transmitted by only one route (e.g. direct/indirect contact and/or faecal-orally), it is now apparent that the aerosol transmission route is also possible and opportunistic, depending on any potentially aerosol-generating procedures, the severity of illness and the degree and duration of pathogen-shedding in the infected patient, as well as the environment in which these activities are conducted.This article reviews the evidence and characteristics of some of the accepted (tuberculosis, measles, chickenpox, whooping cough) and some of the more opportunistic (influenza, Clostridium difficile, norovirus) aerosol-transmitted infectious agents and outlines methods of detecting and quantifying transmission.

Relationships among dissemination of primary parainfluenza virus infection in the respiratory tract, mucosal and peripheral immune responses, and protection from reinfection: a noninvasive bioluminescence-imaging study

Respiratory paramyxoviruses such as respiratory syncytial virus (RSV) and human parainfluenza virus type 1 (HPIV1) to HPIV4 infect virtually all children by the age of 2 to 5 years, leading to partial but incomplete protection from reinfection. Here, we used luciferase-expressing reporter Sendai viruses (the murine counterpart of HPIV1) to noninvasively measure primary infection, immune responses, and protection from reinfection by either a lethal challenge or natural transmission in living mice. Both nonattenuated and attenuated reporter Sendai viruses were used, and three inoculation strategies were employed: intramuscular (i.m.), intranasal (i.n.) at a low dose and low volume, and i.n. at a high dose and high volume. High-dose, high-volume i.n. inoculation resulted in the highest levels of antibody responses and protection from reinfection. Low-dose, low-volume i.n. inoculation afforded complete protection from contact transmission and protection from morbidity, mortality, and viral growth during lethal challenge. i.m. inoculation was inferior to i.n. inoculation at inducing antibody responses and protection from challenge. For individual mice and across groups, the levels of serum binding and neutralizing antibody responses correlated with primary infection and protection from reinfection in the lungs. Contact transmission, the predominant mode of parainfluenza virus transmission, was modeled accurately by direct i.n. inoculation of Sendai virus at a low dose and low volume and was completely preventable by i.n. vaccination of an attenuated virus at a low dose and low volume. The data highlight differences in infection and protection from challenge in the upper versus lower respiratory tract and bear upon live attenuated vaccine development.

IMPORTANCE

There are currently no licensed vaccines against HPIVs and human RSV (HRSV), important respiratory pathogens of infants and children. Natural infection leads to partial but incomplete protective immunity, resulting in subsequent reinfections even in the absence of antigenic drift. Here, we used noninvasive bioluminescence imaging in a mouse model to dissect relationships among (i) the mode of inoculation, (ii) the dynamics of primary infection, (iii) consequent immune responses, and (iv) protection from high-dose, high-volume lethal challenge and contact transmission, which we find here to be similar to that of a mild low-dose, low-volume upper respiratory tract (URT)-biased infection. Our studies demonstrate the superiority of i.n. versus i.m. vaccination in protection against both lethal challenge and contact transmission. In addition to providing correlates of protection that will assist respiratory virus vaccine development, these studies extend the development of an increasingly used technique for the study of viral infection and immunity, noninvasive bioluminescence imaging.

Modes of transmission of influenza B virus in households

Introduction

While influenza A and B viruses can be transmitted via respiratory droplets, the importance of small droplet nuclei “aerosols” in transmission is controversial.

Methods and Findings

In Hong Kong and Bangkok, in 2008–11, subjects were recruited from outpatient clinics if they had recent onset of acute respiratory illness and none of their household contacts were ill. Following a positive rapid influenza diagnostic test result, subjects were randomly allocated to one of three household-based interventions: hand hygiene, hand hygiene plus face masks, and a control group. Index cases plus their household contacts were followed for 7–10 days to identify secondary infections by reverse transcription polymerase chain reaction (RT-PCR) testing of respiratory specimens. Index cases with RT-PCR-confirmed influenza B were included in the present analyses. We used a mathematical model to make inferences on the modes of transmission, facilitated by apparent differences in clinical presentation of secondary infections resulting from aerosol transmission. We estimated that approximately 37% and 26% of influenza B virus transmission was via the aerosol mode in households in Hong Kong and Bangkok, respectively. In the fitted model, influenza B virus infections were associated with a 56%–72% risk of fever plus cough if infected via aerosol route, and a 23%–31% risk of fever plus cough if infected via the other two modes of transmission.

Conclusions

Aerosol transmission may be an important mode of spread of influenza B virus. The point estimates of aerosol transmission were slightly lower for influenza B virus compared to previously published estimates for influenza A virus in both Hong Kong and Bangkok. Caution should be taken in interpreting these findings because of the multiple assumptions inherent in the model, including that there is limited biological evidence to date supporting a difference in the clinical features of influenza B virus infection by different modes.