Monkeypox virus in liver and spleen of child in Gabon

Infection prevention and control measures to reduce the transmission of mpox: A systematic review

OBJECTIVES

To make inferences regarding the effectiveness of respiratory interventions and case isolation measures in reducing or preventing the transmission of mpox based on synthesis of available literature.

METHODS

The WHO Clinical Management and Infection Prevention and Control 2022 guideline and droplet precautions in healthcare facilities and home isolation infection prevention control measures for patients with mpox. We conducted a systematic review that included a broad search of five electronic databases. In a two-stage process, we initially sought only randomized controlled trials and observational comparative studies; when the search failed to yield eligible studies, the subsequent search included all study designs including clinical and environmental sampling studies.

RESULTS

No studies were identified that directly addressed airborne and droplet precautions and home isolation infection prevention control measures. To inform the review questions the review team synthesized route of transmission data in mpox. There were 2366/4309 (54.9%) cases in which investigators identified mpox infection occurring following transmission through direct physical sexual contact. There were no reported mpox cases in which investigators identified inhalation as a single route of transmission. There were 2/4309 cases in which investigators identified fomite as a single route of transmission. Clinical and environmental sampling studies isolated mpox virus in a minority of saliva, oropharangeal swabs, mpox skin lesions, and hospital room air.

CONCLUSIONS

Current findings provide compelling evidence that transmission of mpox occurs through direct physical contact. Because investigators have not reported any cases of transmission via inhalation alone, the impact of airborne and droplet infection prevention control measures in reducing transmission will be minimal. Avoiding physical contact with others, covering mpox lesions and wearing a medical mask is likely to reduce onward mpox transmission; there may be minimal reduction in transmission from additionally physically isolating patients with mild disease at home.

The Changing Global Epidemiology of Re-emerging Human Monkeypox Virus Infection: A Systematic Review

Human monkeypox virus (MPVX) infection represents an emerging zoonotic disease caused by an orthopoxvirus, resulting in a condition reminiscent of smallpox. More recent developments have witnessed a notable surge in global MPVX outbreaks, eliciting significant concerns. We aimed to investigate the epidemiological factors of the emerging human monkeypox virus infection, including the number of suspected, confirmed, and fatal cases, as well as the risk factors for contracting monkeypox infection. We performed a systematic review of peer-reviewed literature by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic database search (PubMed, Wiley Online Library, and Science Direct) was undertaken. For monkeypox-related studies, we included 25 peer-reviewed articles from 2018 and 2022, and data were extracted on the current evidence on the cases and the risk factors for MPVX infection, to develop public health advisories. Our reports show a rapid rise of MPVX cases in the highly endemic African regions after the 1970s, spread to other countries, and an increase in the median age from young children to young adults. The cessation of smallpox vaccination might have been one of the factors responsible for these findings. As of 2022, the genomic sequences of ten MPVX strains associated with the recent countrywide outbreak have been determined. While the West African Clade has been primarily implicated in the recent viral surge, data were insufficient to determine which mutation contributed to increased transmissibility. In the Democratic Republic of the Congo (DRC), sleeping on the floor was significantly associated with contracting MPVX, while eating or processing of animal foods was not a significant risk factor. In the United States, cleaning the cages and bedding of sick animals, touching infected animals, and daily exposure to sick animals were associated with an increased probability of contracting the MPVX infection. Recent global outbreaks and the rising incidence of MPVX infections among young adults in the endemic zones might be a result of the cessation of the smallpox vaccine. The increased risk associated with exposure to sick animals or sleeping on the floor suggests high infectivity from animal excretions. Increasing awareness, strict surveillance, and contact tracing can help contain global outbreaks. The ring vaccination approach for exposed individuals is another potential disease containment strategy. Future studies should investigate measures for rapid laboratory diagnosis, maintaining lab safety, and transmissibility.

Epidemiology, host range, and associated risk factors of monkeypox: an emerging global public health threat

Based on recent multiregional epidemiological investigations of Monkeypox (MPX), on 24 July 2022, the World Health Organization declared it a global public health threat. Retrospectively MPX was an ignored zoonotic endemic infection to tropical rainforest regions of Western and Central African rural communities until a worldwide epidemic in May 2022 verified the potential threat of monkeypox virus (MPXV) to be propagated across the contemporary world via transnational tourism and animal movements. During 2018-2022, different cases of MPX diagnosed in Nigerian travelers have been documented in Israel, the United Kingdom, Singapore, and the United States. More recently, on 27 September 2022, 66,000 MPX cases have been confirmed in more than 100 non-endemic countries, with fluctuating epidemiological footprinting from retrospective epidemics. Particular disease-associated risk factors fluctuate among different epidemics. The unpredicted appearance of MPX in non-endemic regions suggests some invisible transmission dynamic. Hence, broad-minded and vigilant epidemiological attention to the current MPX epidemic is mandatory. Therefore, this review was compiled to highlight the epidemiological dynamic, global host ranges, and associated risk factors of MPX, concentrating on its epidemic potential and global public health threat.

Clinical features and management of individuals admitted to hospital with monkeypox and associated complications across the UK: a retrospective cohort study

BACKGROUND

The scale of the 2022 global mpox (formerly known as monkeypox) outbreak has been unprecedented. In less than 6 months, non-endemic countries have reported more than 67 000 cases of a disease that had previously been rare outside of Africa. Mortality has been reported as rare but hospital admission has been relatively common. We aimed to describe the clinical and laboratory characteristics and outcomes of individuals admitted to hospital with mpox and associated complications, including tecovirimat recipients.

METHODS

In this cohort study, we undertook retrospective review of electronic clinical records and pathology data for all individuals admitted between May 6, and Aug 3, 2022, to 16 hospitals from the Specialist and High Consequence Infectious Diseases Network for Monkeypox. The hospitals were located in ten cities in England and Northern Ireland. Inclusion criteria were clinical signs consistent with mpox and MPXV DNA detected from at least one clinical sample by PCR testing. Patients admitted solely for isolation purposes were excluded from the study. Key outcomes included admission indication, complications (including pain, secondary infection, and mortality) and use of antibiotic and anti-viral treatments. Routine biochemistry, haematology, microbiology, and virology data were also collected. Outcomes were assessed in all patients with available data.

FINDINGS

156 individuals were admitted to hospital with complicated mpox during the study period. 153 (98%) were male and three (2%) were female, with a median age of 35 years (IQR 30-44). Gender data were collected from electronic patient records, which encompassed full formal review of clincian notes. The prespecified options for data collection for gender were male, female, trans, non-binary, or unknown. 105 (71%) of 148 participants with available ethnicity data were of White ethnicity and 47 (30%) of 155 were living with HIV with a median CD4 count of 510 cells per mm3 (IQR 349-828). Rectal or perianal pain (including proctitis) was the most common indication for hospital admission (44 [28%] of 156). Severe pain was reported in 89 (57%) of 156, and secondary bacterial infection in 82 (58%) of 142 individuals with available data. Median admission duration was 5 days (IQR 2-9). Ten individuals required surgery and two cases of encephalitis were reported. 38 (24%) of the 156 individuals received tecovirimat with early cessation in four cases (two owing to hepatic transaminitis, one to rapid treatment response, and one to patient choice). No deaths occurred during the study period.

INTERPRETATION

Although life-threatening mpox appears rare in hospitalised populations during the current outbreak, severe mpox and associated complications can occur in immunocompetent individuals. Analgesia and management of superimposed bacterial infection are priorities for patients admitted to hospital.

FUNDING

None.

Clinical and Epidemiological Interventions for Monkeypox Management in Children: A Systematic Review

This review aims to compile the available literature on monkeypox, identify risk factors for developing the disease, and recommend effective preventative methods to reduce the number of reported cases and fatalities in children and pregnant women. In seeking out pertinent studies on monkeypox virus in children and pregnant women, we searched the literature using the databases Cochrane Library, Google Scholar, PubMed, EMBASE, Web of Science, and Scopus up to 1st February 2023. This study analyzed data from case studies of monkeypox in children and pregnant women. Clinical data and test findings of monkeypox patients less than 18 years old and pregnant women were analyzed. The Newcastle-Ottawa Scale was used to do the quality evaluation. Our record examination spanned the years 1985 to 2023 and found 17 children and five pregnant female patients treated with monkeypox in various hospitals/community centers. Zaire, Gabon, Chicago, Sierra Leone, Central African Republic, Northern DR Congo, Liberia, Cameroon, the Democratic Republic of the Congo, the United Kingdom, the Netherlands, and Florida all contributed to the 14 studies analyzed. There were no studies identified for meta-analysis of selected case studies of hospitalized children and pregnant women who were diagnosed with monkeypox. The incidence, prevalence, clinical characteristics, diagnosis, management, prevention, vaccinations, infant care, and care for expectant mothers are all discussed in this systematic review of monkeypox in children. Our research findings may provide a foundation for further focused research and the development of related recommendations or guidelines.

Identifying the Most Probable Mammal Reservoir Hosts for Monkeypox Virus Based on Ecological Niche Comparisons

Previous human cases or epidemics have suggested that Monkeypox virus (MPXV) can be transmitted through contact with animals of African rainforests. Although MPXV has been identified in many mammal species, most are likely secondary hosts, and the reservoir host has yet to be discovered. In this study, we provide the full list of African mammal genera (and species) in which MPXV was previously detected, and predict the geographic distributions of all species of these genera based on museum specimens and an ecological niche modelling (ENM) method. Then, we reconstruct the ecological niche of MPXV using georeferenced data on animal MPXV sequences and human index cases, and conduct overlap analyses with the ecological niches inferred for 99 mammal species, in order to identify the most probable animal reservoir. Our results show that the MPXV niche covers three African rainforests: the Congo Basin, and Upper and Lower Guinean forests. The four mammal species showing the best niche overlap with MPXV are all arboreal rodents, including three squirrels: Funisciurus anerythrus, Funisciurus pyrropus, Heliosciurus rufobrachium, and Graphiurus lorraineus. We conclude that the most probable MPXV reservoir is F. anerythrus based on two niche overlap metrics, the areas of higher probabilities of occurrence, and available data on MPXV detection.

As the World Struggles With the COVID-19 Pandemic, Another Emergency Threat Arrives on the Horizon, the Monkeypox: A Systematic Review

The whole world got threatened by COVID-19, which made a significant loss in various sectors and pushed the world into a deep valley. Now a new threat, the emerging outbreak of monkeypox is rapidly spreading across the globe and is currently being observed in more than 110 countries with 79,473 confirmed cases and 50 deaths. Data were collected from PubMed, EMBASE, MEDLINE, Cochrane, Scopus database, African Journals OnLine, internet library sub-Saharan Africa, and Google Scholar. Most data were taken from the democratic Republic of Congo, the Central African Republic, Cameroon, the Republic of Congo, Liberia, Nigeria, the US, and the UK. Case reports, outbreak investigations, epidemiological studies, and surveillance studies were reviewed to find epidemiological details about the outbreak. A total of 50 peer-reviewed articles and 20 grey literature articles, including 9050 cases, were identified for data extraction. Our systematic review revealed that the group most affected is male (95.5%), with a median age of 33.8 years. A total of 55% of the transmission was sexually transmitted. The most commonly reported symptoms such as vesicular-pustular rashes (97.54%), fever (55.25%), inguinal lymphadenopathy (53.6%), exanthema (40.21%), fatigue, headache, asthenia (26.32%), myalgia (16.33%), vesicles and ulcers (30.61%) in the anogenital regions were some of the significant findings. The case fatality rate was observed to be up to 8.65%. The most affected country was the USA, which has the most fatalities in younger ages involved in homosexuality, suffering from HIV or sexually transmitted diseases (STDs).

Monkeypox Virus Infections in Humans

Human monkeypox is a viral zoonosis endemic to West and Central Africa that has recently generated increased interest and concern on a global scale as an emerging infectious disease threat in the midst of the slowly relenting COVID-2019 disease pandemic. The hallmark of infection is the development of a flu-like prodrome followed by the appearance of a smallpox-like exanthem. Precipitous person-to-person transmission of the virus among residents of 100 countries where it is nonendemic has motivated the immediate and widespread implementation of public health countermeasures. In this review, we discuss the origins and virology of monkeypox virus, its link with smallpox eradication, its record of causing outbreaks of human disease in regions where it is endemic in wildlife, its association with outbreaks in areas where it is nonendemic, the clinical manifestations of disease, laboratory diagnostic methods, case management, public health interventions, and future directions.

Risk of Monkeypox virus (MPXV) transmission through the handling and consumption of food

Monkeypox (MPX) is a zoonotic infectious disease caused by Monkeypox virus (MPXV), an enveloped DNA virus belonging to the Poxviridae family and the Orthopoxvirus genus. Since early May 2022, a growing number of human cases of Monkeypox have been reported in non-endemic countries, with no history of contact with animals imported from endemic and enzootic areas, or travel to an area where the virus usually circulated before May 2022. This qualitative risk assessment aimed to investigate the probability that MPXV transmission occurs through food during its handling and consumption. The risk assessment used "top-down" (based on epidemiological data) and "bottom-up" (following the agent through the food chain to assess the risk of foodborne transmission to human) approaches, which were combined. The "top-down" approach first concluded that bushmeat was the only food suspected as a source of contamination in recorded cases of MPXV, by contact or ingestion. The "bottom-up" approach then evaluated the chain of events required for a human to become ill after handling or consuming food. This approach involves several conditions: (i) the food must be contaminated with MPXV (naturally, by an infected handler or after contact with a contaminated surface); (ii) the food must contain viable virus when it reaches the handler or consumer; (iii) the person must be exposed to the virus and; (iv) the person must be infected after exposure. Throughout the risk assessment, some data gaps were identified and highlighted. The conclusions of the top-down and bottom-up approaches are consistent and suggest that the risk of transmission of MPXV through food is hypothetical and that such an occurrence was never reported. In case of contamination, cooking (e.g., 12 min at 70°C) could be considered effective in inactivating Poxviridae in foods. Recommendations for risk management are proposed. To our knowledge, this is the first risk assessment performed on foodborne transmission of MPXV.

Comprehensive literature review of monkeypox

The current outbreak of monkeypox (MPX) infection has emerged as a global matter of concern in the last few months. MPX is a zoonosis caused by the MPX virus (MPXV), which is one of the Orthopoxvirus species. Thus, it is similar to smallpox caused by the variola virus, and smallpox vaccines and drugs have been shown to be protective against MPX. Although MPX is not a new disease and is rarely fatal, the current multi-country MPX outbreak is unusual because it is occurring in countries that are not endemic for MPXV. In this work, we reviewed the extensive literature available on MPXV to summarize the available data on the major biological, clinical and epidemiological aspects of the virus and the important scientific findings. This review may be helpful in raising awareness of MPXV transmission, symptoms and signs, prevention and protective measures. It may also be of interest as a basis for performance of studies to further understand MPXV, with the goal of combating the current outbreak and boosting healthcare services and hygiene practices.Trial registration: ClinicalTrials.gov identifier: NCT02977715..Trial registration: ClinicalTrials.gov identifier: NCT03745131..Trial registration: ClinicalTrials.gov identifier: NCT00728689..Trial registration: ClinicalTrials.gov identifier: NCT02080767..

The re-emerging monkeypox disease

BACKGROUND

On 7th May 2022, human monkeypox was identified in the United Kingdom, a non-endemic zone, with subsequent multi-country outbreaks. About 6 weeks later, the European Centre for Disease Prevention and Control reported 1158 confirmed cases in non-endemic countries scattered within the European Economic Area (EEA), and a total of 1882 cases confirmed worldwide, inclusive of the EEA. These numbers are expected to increase with high alert and amplified surveillance established in non-endemic regions. In light of a looming epidemic, current understanding of the virus, and identification of gaps in the literature remain critical hence warranting a scoping review of available literature.

METHODS

Literature searches were performed through PubMed, SCOPUS, ScienceDirect and Hinari to identify studies eligible for inclusion in accordance with PRISMA guidelines.

RESULTS

Seventy-seven articles were included in the review. Majority of the cases were from the Central African clade (n = 29,905) versus the West African clade (n = 252). 6/16 articles that reported vaccination status stated that none of the cases were vaccinated. In the remaining articles, approximately 80%-96% cases were unvaccinated. It was noted that 4%-21% of the vaccinated individuals got infected. The secondary attack rate ranged from 0% to 10.2%, while the calculated pooled estimated case fatality rate was 8.7%.

CONCLUSION

This scoping review provides an extensive look at our current understanding on monkeypox disease. Further studies are needed to better understand its risk factors, genetics and natural history, in order for public health strategists to generate prevention strategies and management decisions.

Rapid Adaptation of Established High-Throughput Molecular Testing Infrastructure for Monkeypox Virus Detection

Beginning in May 2022, a rising number of monkeypox cases were reported in non-monkeypox-endemic countries in the Northern Hemisphere. We adapted 2 published quantitative PCRs for use as a dual-target monkeypox virus test on widely used automated high-throughput PCR systems. We determined analytic performance by serial dilutions of monkeypox virus reference material, which we quantified by digital PCR. We found the lower limit of detection for the combined assays was 4.795 (95% CI 3.6-8.6) copies/mL. We compared clinical performance against a commercial manual orthopoxvirus research use only PCR kit by using clinical remnant swab samples. Our assay showed 100% positive (n = 11) and 100% negative (n = 56) agreement. Timely and scalable PCR tests are crucial for limiting further spread of monkeypox. The assay we provide streamlines high-throughput molecular testing for monkeypox virus on existing broadly established platforms used for SARS-CoV-2 diagnostic testing.

Monkeypox: A clinical update for paediatricians

The global spread of human monkeypox disease, a zoonotic infection related to smallpox and endemic to West and Central Africa, presents serious challenges for health systems. As of July 2022, 14 533 cases have been reported world-wide, leading to designation as a Public Health Emergency of International Concern. Monkeypox disease is spread from animals to humans through infected lesions or fluids; human-human transmission occurs through fomites, droplets or direct contact. Illness is usually self-limiting, but severe disease can occur in specific groups - particularly children, and people who are immunocompromised or pregnant. Clinical presentation may include fever, lymphadenopathy and skin rash, but the rash may occur without other symptoms. Complications can include secondary bacterial infection of skin lesions, vision loss from corneal involvement, pneumonia, sepsis and encephalitis. Diagnosis of monkeypox requires consideration of epidemiological, clinical and laboratory findings, with sensitive history-taking, to elicit close contacts, critical. Supportive management is usually sufficient, but treatment options (where required) include antivirals and vaccinia immune globulin. A paucity of safety data for relevant antivirals may limit their use. There are two types of monkeypox vaccines: a replication-competent vaccinia vaccine, the use of which is logistically and clinically complex, and a replication-deficient modified vaccinia Ankara virus vaccine. Preparedness of health systems for addressing the current outbreak is constrained by historic underfunding for research, and compounded by stigma and discrimination against cases and affected communities. Key challenges in halting transmission include improving vaccine equity and countering discrimination against men who have sex with men to aid diagnosis and treatment.

Monkeypox: A Contemporary Review for Healthcare Professionals

The ongoing 2022 multicountry outbreak of monkeypox is the largest in history to occur outside of Africa. Monkeypox is an emerging zoonotic disease that for decades has been viewed as an infectious disease with significant epidemic potential because of the increasing occurrence of human outbreaks in recent years. As public health entities work to contain the current outbreak, healthcare professionals globally are aiming to become familiar with the various clinical presentations and management of this infection. We present in this review an updated overview of monkeypox for healthcare professionals in the context of the ongoing outbreaks around the world.

A systematic review of the epidemiology of human monkeypox outbreaks and implications for outbreak strategy

Monkeypox is a vesicular-pustular illness that carries a secondary attack rate in the order of 10% in contacts unvaccinated against smallpox. Case fatality rates range from 1 to 11%, but scarring and other sequelae are common in survivors. It continues to cause outbreaks in remote populations in Central and West Africa, in areas with poor access and weakened or disrupted surveillance capacity and information networks. Recent outbreaks in Nigeria (2017-18) and Cameroon (2018) have occurred where monkeypox has not been reported for over 20 years. This has prompted concerns over whether there have been changes in the biology and epidemiology of the disease that may in turn have implications for how outbreaks and cases should best be managed. A systematic review was carried out to examine reported data on human monkeypox outbreaks over time, and to identify if and how epidemiology has changed. Published and grey literature were critically analysed, and data extracted to inform recommendations on outbreak response, use of case definitions and public health advice. The level of detail, validity of data, geographical coverage and consistency of reporting varied considerably across the 71 monkeypox outbreak documents obtained. An increase in cases reported over time was supported by literature from the Democratic Republic of Congo (DRC). Data were insufficient to measure trends in secondary attack rates and case fatality rates. Phylogenetic analyses consistently identify two strains of the virus without evidence of emergence of a new strain. Understanding of monkeypox virulence with regard to clinical presentation by strain is minimal, with infrequent sample collection and laboratory analysis. A variety of clinical and surveillance case definitions are described in the literature: two definitions have been formally evaluated and showed high sensitivity but low specificity. These were specific to a Congo-Basin (CB) strain-affected area of the DRC where they were used. Evidence on use of antibiotics for prophylaxis against secondary cutaneous infection is anecdotal and limited. Current evidence suggests there has been an increase in total monkeypox cases reported by year in the DRC irrespective of advancements in the national Integrated Disease Surveillance and Response (IDSR) system. There has been a marked increase in number of individual monkeypox outbreak reports, from outside the DRC in between 2010 and 2018, particularly in the Central African Republic (CAR) although this does not necessarily indicate an increase in annual cases over time in these areas. The geographical pattern reported in the Nigeria outbreak suggests a possible new and widespread zoonotic reservoir requiring further investigation and research. With regards to outbreak response, increased attention is warranted for high-risk patient groups, and nosocomial transmission risks. The animal reservoir remains unknown and there is a dearth of literature informing case management and successful outbreak response strategies. Up-to-date complete, consistent and longer-term research is sorely needed to inform and guide evidence-based response and management of monkeypox outbreaks.

A phylogeographic investigation of African monkeypox

Monkeypox is a zoonotic disease caused by a virus member of the genus Orthopoxvirus and is endemic to Central and Western African countries. Previous work has identified two geographically disjuct clades of monkeypox virus based on the analysis of a few genomes coupled with epidemiological and clinical analyses; however, environmental and geographic causes of this differentiation have not been explored. Here, we expand previous phylogenetic studies by analyzing a larger set of monkeypox virus genomes originating throughout Sub-Saharan Africa to identify possible biogeographic barriers associated with genetic differentiation; and projected ecological niche models onto environmental conditions at three periods in the past to explore the potential role of climate oscillations in the evolution of the two primary clades. Analyses supported the separation of the Congo Basin and West Africa clades; the Congo Basin clade shows much shorter branches, which likely indicate a more recent diversification of isolates within this clade. The area between the Sanaga and Cross Rivers divides the two clades and the Dahomey Gap seems to have also served as a barrier within the West African clade. Contraction of areas with suitable environments for monkeypox virus during the Last Glacial Maximum, suggests that the Congo Basin clade of monkeypox virus experienced a severe bottleneck and has since expanded its geographic range.

Intrabronchial inoculation of cynomolgus macaques with cowpox virus

The public health threat of orthopoxviruses from bioterrorist attacks has prompted researchers to develop suitable animal models for increasing our understanding of viral pathogenesis and evaluation of medical countermeasures (MCMs) in compliance with the FDA Animal Efficacy Rule. We present an accessible intrabronchial cowpox virus (CPXV) model that can be evaluated under biosafety level-2 laboratory conditions. In this dose-ranging study, utilizing cynomolgus macaques, signs of typical orthopoxvirus disease were observed with the lymphoid organs, liver, skin (generally mild) and respiratory tract as target tissues. Clinical and histopathological evaluation suggests that intrabronchial CPXV recapitulated many of the features of monkeypox and variola virus, the causative agent of smallpox, infections in cynomolgus macaque models. These similarities suggest that CPXV infection in non-human primates should be pursued further as an alternative model of smallpox. Further development of the CPXV primate model, unimpeded by select agent and biocontainment restrictions, should facilitate the development of MCMs for smallpox.

[Human monkeypox]

Unlike other recent viral emergences, which were in majority caused by RNA viruses, the monkeypox results from infection by a DNA virus, an orthopoxvirus closely related to both vaccine and smallpox viruses and whose two genomic variants are known. Unexpectedly isolated from captive Asiatic monkeys and first considered as an laboratory curiosity, this virus was recognised in 1970 as an human pathogen in tropical Africa. Here it was responsible for sporadic cases following intrusions (for hunting) into tropical rain forests or rare outbreak with human-to-human transmission as observed in 1996 in Democratic Republic of Congo. As monkeypox in humans is not distinguishable from smallpox (a disease globally eradicated in 1977) it was only subjected to vigilant epidemiological surveillance and not considered as a potential threat outside Africa. This point of view radically changed in 2003 when monkeypox was introduced in the USA by African wild rodents and spread to 11 different states of this country. Responsible for 82 infections in American children and adults, this outbreak led to realize the sanitary hazards resulting from international trade of exotic animals and scientific investigations increasing extensively our knowledge of this zoonosis.

The pathology of experimental aerosolized monkeypox virus infection in cynomolgus monkeys (Macaca fascicularis)

Cynomolgus monkeys (Macaca fascicularis) were exposed by fine-particle aerosol to lethal doses of monkeypox virus, Zaire strain. Death, attributable to fibrinonecrotic bronchopneumonia, occurred 9 to 17 days postexposure. Lower airway epithelium served as the principal target for primary infection. The relative degree of involvement among lymphoid tissues suggested that tonsil, mediastinal, and mandibular lymph nodes were also infected early in the course of the disease, and may have served as additional, although subordinate, sites of primary replication. The distribution of lesions was consistent with lymphatogenous spread to the mediastinal lymph nodes and systemic dissemination of the virus through a monocytic cell-associated viremia. This resulted in lesions affecting other lymph nodes, the thymus, spleen, skin, oral mucosa, gastrointestinal tract, and reproductive system. The mononuclear phagocyte/dendritic cell system was the principal target within lymphoid tissues and may also have provided the means of entry into other systemic sites. Hepatic involvement was uncommon. Lesions at all affected sites were characterized morphologically as necrotizing. Terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining of select lesions suggested that cell death within lymphoid and epithelial tissues was due in large part to apoptosis. Skin and mucosal surfaces of the respiratory and gastrointestinal tracts also exhibited variable proliferation of epithelial cells and subjacent fibroblasts. Epithelial intracytoplasmic inclusion bodies, consistent with Guarnieri bodies, were usually inconspicuous by light microscopy, but when present, were most readily apparent in the stratified squamous epithelium of the oral mucosa and epidermis. Multinucleated syncytial cells were also occasionally observed in the stratified squamous epithelium of the tongue, tonsil, and skin, and in the intestinal mucosa. Monkeypox virus antigen was readily demonstrated by immunohistochemistry using anti-vaccinia mouse polyclonal antibodies as well as anti-monkeypox rabbit polyclonal antibodies. Detectable poxviral antigen was limited to sites exhibiting obvious morphologic involvement and was most prominent within epithelial cells, macrophages, dendritic cells, and fibroblasts of affected tissues. The presence of poxviral antigen, as determined by immunohistochemistry, correlated with ultrastructural identification of replicating virus. Concurrent bacterial septicemia, present in one monkey, was associated with increased dissemination of the virus to the liver, spleen, and bone marrow and resulted in a more rapidly fatal clinical course.