Autopsy series of 68 cases dying before and during the 1918 influenza pandemic peak

SARS-CoV-2 Spike Protein 1 Causes Aggregation of α-Synuclein via Microglia-Induced Inflammation and Production of Mitochondrial ROS: Potential Therapeutic Applications of Metformin

Abnormal aggregation of α-synuclein is the hallmark of neurodegenerative diseases, classified as α-synucleinopathies, primarily occurring sporadically. Their onset is associated with an interaction between genetic susceptibility and environmental factors such as neurotoxins, oxidative stress, inflammation, and viral infections. Recently, evidence has suggested an association between neurological complications in long COVID (sometimes referred to as 'post-acute sequelae of COVID-19') and α-synucleinopathies, but its underlying mechanisms are not completely understood. In this study, we first showed that SARS-CoV-2 Spike protein 1 (S1) induces α-synuclein aggregation associated with activation of microglial cells in the rodent model. In vitro, we demonstrated that S1 increases aggregation of α-synuclein in BE(2)M-17 dopaminergic neurons via BV-2 microglia-mediated inflammatory responses. We also identified that S1 directly affects aggregation of α-synuclein in dopaminergic neurons through increasing mitochondrial ROS, though only under conditions of sufficient α-Syn accumulation. In addition, we observed a synergistic effect between S1 and the neurotoxin MPP+ S1 treatment. Combined with a low dose of MPP+, it boosted α-synuclein aggregation and mitochondrial ROS production compared to S1 or the MPP+ treatment group. Furthermore, we evaluated the therapeutic effects of metformin. The treatment of metformin suppressed the S1-induced inflammatory response and α-synucleinopathy. Our findings demonstrate that S1 promotes α-synucleinopathy via both microglia-mediated inflammation and mitochondrial ROS, and they provide pathological insights, as well as a foundation for the clinical management of α-synucleinopathies and the onset of neurological symptoms after the COVID-19 outbreak.

Two complete 1918 influenza A/H1N1 pandemic virus genomes characterized by next-generation sequencing using RNA isolated from formalin-fixed, paraffin-embedded autopsy lung tissue samples along with evidence of secondary bacterial co-infection

The 1918 influenza pandemic was the most devastating respiratory pandemic in modern human history, with 50-100 million deaths worldwide. Here, we characterized the complete genomes of influenza A virus (IAV) from two fatal cases during the fall wave of 1918 influenza A (H1N1) pandemic in the United States, one from Walter Reed Army Hospital in Washington, DC, and the other from Camp Jackson, SC. The two complete IAV genomes were obtained by combining Illumina deep sequencing data from both total RNA and influenza viral genome-enriched libraries along with Sanger sequencing data from PCR across the sequencing gaps. This study confirms the previously reported 1918 IAV genomes and increases the total number of available complete or near-complete influenza viral genomes of the 1918 pandemic from four to six. Sequence comparisons among them confirm that the genomes of the 1918 pandemic virus were highly conserved during the main wave of the pandemic with geographic separation in North America and Europe. Metagenomic analyses revealed bacterial co-infections in both cases. Interestingly, in the Washington, DC, case, evidence is presented of the first reported Rhodococcus-influenza virus co-infection.

IMPORTANCE

This study applied modern molecular biotechnology and high-throughput sequencing to formalin-fixed, paraffin-embedded autopsy lung samples from two fatal cases during the fall wave of the 1918 influenza A (H1N1) pandemic in the United States. Complete influenza genomes were obtained from both cases, which increases the total number of available complete or near-complete influenza genomes of the 1918 pandemic virus from four to six. Sequence analysis confirms that the 1918 pandemic virus was highly conserved during the main wave of the pandemic with geographic separation in North America and Europe. Metagenomic analyses revealed bacterial co-infections in both cases, including the first reported evidence of Rhodococcus-influenza co-infection. Overall, this study offers a detailed view at the molecular level of the very limited samples from the most devastating influenza pandemic in modern human history.

Have Diagnostics, Therapies, and Vaccines Made the Difference in the Pandemic Evolution of COVID-19 in Comparison with "Spanish Flu"?

In 1918 many countries, but not Spain, were fighting World War I. Spanish press could report about the diffusion and severity of a new infection without censorship for the first-time, so that this pandemic is commonly defined as "Spanish flu", even though Spain was not its place of origin. "Spanish flu" was one of the deadliest pandemics in history and has been frequently compared with the coronavirus disease (COVID)-19 pandemic. These pandemics share similarities, being both caused by highly variable and transmissible respiratory RNA viruses, and diversity, represented by diagnostics, therapies, and especially vaccines, which were made rapidly available for COVID-19, but not for "Spanish flu". Most comparison studies have been carried out in the first period of COVID-19, when these resources were either not yet available or their use had not long started. Conversely, we wanted to analyze the role that the advanced diagnostics, anti-viral agents, including monoclonal antibodies, and innovative COVID-19 vaccines, may have had in the pandemic containment. Early diagnosis, therapies, and anti-COVID-19 vaccines have markedly reduced the pandemic severity and mortality, thus preventing the collapse of the public health services. However, their influence on the reduction of infections and re-infections, thus on the transition from pandemic to endemic condition, appears to be of minor relevance. The high viral variability of influenza and coronavirus may probably be contained by the development of universal vaccines, which are not easy to be obtained. The only effective weapon still remains the disease prevention, to be achieved with the reduction of promiscuity between the animal reservoirs of these zoonotic diseases and humans.

Lost Lessons of the 1918 Influenza: The 1920s Working Hypothesis, the Public Health Paradigm, and the Prevention of Deadly Pandemics

In standard historical accounts, the hyperlethal 1918 flu pandemic was inevitable once a novel influenza virus appeared. However, in the years following the pandemic, it was obvious to distinguished flu experts from around the world that social and environmental conditions interacted with infectious agents and could enhance the virulence of flu germs. On the basis of the timing and geographic pattern of the pandemic, they hypothesized that an "essential cause" of the pandemic's extraordinary lethality was the extreme, prolonged, and industrial-scale overcrowding of US soldiers in World War I, particularly on troopships. This literature synthesis considers research from history, public health, military medicine, veterinary science, molecular genetics, virology, immunology, and epidemiology. Arguments against the hypothesis do not provide disconfirming evidence. Overall, the findings are consistent with an immunologically similar virus varying in virulence in response to war-related conditions. The enhancement-of-virulence hypothesis deserves to be included in the history of the pandemic and the war. These lost lessons of 1918 point to possibilities for blocking the transformation of innocuous infections into deadly disasters and are relevant beyond influenza for diseases like COVID-19. (Am J Public Health. 2022;112(10):1454-1464. https://doi.org/10.2105/AJPH.2022.306976).

Rezende R, G. Machado M, Cagnina RE, Shay AE, C. Garcia C, Nijmeh J, M. Teixeira M, Levy BD. Cysteinyl Maresins Reprogram Macrophages to Protect Mice from Streptococcus pneumoniae after Influenza A Virus Infection

Influenza A virus (IAV) infections are a leading cause of mortality worldwide. Excess mortality during IAV epidemics and pandemics is attributable to secondary bacterial infections, particularly pneumonia caused by Streptococcus pneumoniae. Resident alveolar macrophages (rAMs) are early responders to respiratory infections that coordinate initial host defense responses. Maresin conjugates in tissue regeneration (MCTRs) are recently elucidated cysteinyl maresins that are produced by and act on macrophages. Roles for MCTRs in responses to respiratory infections remain to be determined. Here, IAV infection led to transient decreases in rAM numbers. Repopulated lung macrophages displayed transcriptional alterations 21 days post-IAV with prolonged susceptibility to secondary pneumococcal infection. Administration of a mix of MCTR1 to 3 or MCTR3 alone post-IAV decreased lung inflammation and bacterial load 48 and 72 h after secondary pneumococcal infection. MCTR-exposed rAMs had increased migration and phagocytosis of Streptococcus pneumoniae, reduced secretion of CXCL1, and a reversion toward baseline levels of several IAV-induced pneumonia susceptibility genes. Together, MCTRs counter regulated post-IAV changes in rAMs to promote a rapid return of bacteria host defense. IMPORTANCE Secondary bacterial pneumonia is a serious and common complication of IAV infection, leading to excess morbidity and mortality. New host-directed approaches are needed to complement antibiotics to better address this important global infectious disease. Here, we show that harnessing endogenous resolution mechanisms for inflammation by exogenous administration of a family of specialized proresolving mediators (i.e., cys-MCTRs) increased macrophage resilience mechanisms after IAV to protect against secondary infection from Streptococcus pneumoniae.

The Spanish Flu

The Spanish flu occurred at the end of the First World War, in disastrous epidemiological conditions on populations exhausted by four years of war. At that time, there were no vaccines, no antibiotics, no oxygen and no resuscitation. It was even thought that the infectious agent was a bacterium. Humanity was poorly equipped to fight against a pandemic that caused 50-100 million deaths. The first palpable signs of the outbreak were the rapidly spreading multiple epidemics among young recruits in the American military training camps in March 1918. The flu then spread to the civilian populations and circled the globe twice, sparing no country, even the most remote islands, in tropical as well as polar climates, evolving in successive waves up until April 1919. The first was mild (lethality 0.21%), the second was lethal (lethality 2-4%), and during the third wave, lethality declined (1%), after which the flu became seasonal, with low lethality (0.1%). Between 20 and 40 years of age, patients often died within a few days of pneumonia, with respiratory distress leading to cyanosis, frequently associated with bacterial superinfection. The influenza virus, Myxovirus influenzae, was first discovered in 1931 by Richard Shope in pigs, and then in 1933 by Wilson Smith, Patrick Laidlaw and Christopher Andrews in humans during a seasonal influenza epidemic in London. In 1943, it was first observed under the electron microscope. Hemagglutinin and neuraminidase, the two main virulence factors, were discovered in the 1940s by George Hirst and Alfred Gottschalk. An RNA virus composed of 13,500 nucleotides in eight segments, it was initially sequenced in the 1980s, when Jeffrey Taubenberger determined the complete nucleotide sequence of the 1918 virus from lung tissue samples from patients who died of influenza. The 1918 H1N1 virus was found to have originated in birds. In 2005, it was successfully resuscitated in cell culture. It is 40,000 times more virulent in primates than the seasonal H1N1 virus. The lethality of the second wave could have been due to mutations in the hemagglutinin H1 gene, which would have resulted in a stronger affinity for α,2-6 galactose sialic acids, the virus' receptors on human epithelial cells. That said, the origin of the Spanish flu virus remains controversial. It probably emerged and circulated in the population before March 1918 in America, although European origin has also been evoked. The high mortality in the 20-40 age group remains an enigma. Some experts point to reduced immune response in patients previously exposed to related viral hemagglutinins during the 1889 pandemic. In any event, even though it concerns a markedly different virus, the history of the Spanish flu sheds light on the difficulties of management during today's pandemic.

Archival influenza virus genomes from Europe reveal genomic variability during the 1918 pandemic

The 1918 influenza pandemic was the deadliest respiratory pandemic of the 20th century and determined the genomic make-up of subsequent human influenza A viruses (IAV). Here, we analyze both the first 1918 IAV genomes from Europe and the first from samples prior to the autumn peak. 1918 IAV genomic diversity is consistent with a combination of local transmission and long-distance dispersal events. Comparison of genomes before and during the pandemic peak shows variation at two sites in the nucleoprotein gene associated with resistance to host antiviral response, pointing at a possible adaptation of 1918 IAV to humans. Finally, local molecular clock modeling suggests a pure pandemic descent of seasonal H1N1 IAV as an alternative to the hypothesis of origination through an intrasubtype reassortment.

For archival pathogens, like pH1N1 Influenza A virus the causative agent of 1918/19 pandemic, only few whole genome sequences exist. Here, Patrono et al. provide one complete and two partial genomes from Germany and find variation in two sites in the nucleoprotein gene in pandemic samples compared to pre-pandemic samples, that are associated with resistance to host antiviral response, pointing at a possible viral adaptation to humans.

Bacterial coinfection in influenza pneumonia: Rates, pathogens, and outcomes

BACKGROUND

Evidence from pandemics suggests that influenza is often associated with bacterial coinfection. Among patients hospitalized for influenza pneumonia, we report the rate of coinfection and distribution of pathogens, and we compare outcomes of patients with and without bacterial coinfection.

METHODS

We included adults admitted with community-acquired pneumonia (CAP) and tested for influenza from 2010 to 2015 at 179 US hospitals participating in the Premier database. Pneumonia was identified using an International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) algorithm. We used multiple logistic and gamma-generalized linear mixed models to assess the relationships between coinfection and inpatient mortality, intensive care unit (ICU) admission, length of stay, and cost.

RESULTS

Among 38,665 patients hospitalized with CAP and tested for influenza, 4,313 (11.2%) were positive. In the first 3 hospital days, patients with influenza were less likely than those without to have a positive culture (10.3% vs 16.2%; P < .001), and cultures were more likely to contain Staphylococcus aureus (34.2% vs 28.2%; P = .007) and less likely to contain Streptococcus pneumoniae (24.9% vs 31.0%; P = .008). Of S. aureus isolates, 42.8% were methicillin resistant among influenza patients versus 53.2% among those without influenza (P = .01). After hospital day 3, pathogens for both groups were similar. Bacterial coinfection was associated with increased odds of in-hospital mortality (aOR, 3.00; 95% CI, 2.17-4.16), late ICU transfer (aOR, 2.83; 95% CI, 1.98-4.04), and higher cost (risk-adjusted mean multiplier, 1.77; 95% CI, 1.59-1.96).

CONCLUSIONS

In a large US inpatient sample hospitalized with influenza and CAP, S. aureus was the most frequent cause of bacterial coinfection. Coinfection was associated with worse outcomes and higher costs.

A case of influenza-associated invasive aspergillosis with cerebral hemorrhage due to infectious vasculopathy

An invasive aspergillosis (IA) primarily occurs among immunocompromised patients. Recently with an influenzae infection prevalently spreading, influenzae-associated invasive aspergillosis (IAIA) has been reported occasionally. By contrast, neuroleptic malignant syndrome (NMS) occurs rarely in psychiatric patients who are treated with Olanzapine. We report a 43 years old male with psychiatric disorder who had developed IAIA followed by NMS and cerebral hemorrhage as the result of aspergillus invasion to cerebral vessels. He had also super-infection of COVID-19, 13 months later to be saved completely after invasive mechanical respiratory supports. From clinical aspects, we would emphasize that it is of importance to find earlier co-occurrence of IAIA patients with cerebral hemorrhage due to secondary infectious vasculopathy of IA.

Microorganisms as Shapers of Human Civilization, from Pandemics to Even Our Genomes: Villains or Friends? A Historical Approach

Universal history is characterized by continuous evolution, in which civilizations are born and die. This evolution is associated with multiple factors, among which the role of microorganisms is often overlooked. Viruses and bacteria have written or decisively contributed to terrible episodes of history, such as the Black Death in 14th century Europe, the annihilation of pre-Columbian American civilizations, and pandemics such as the 1918 Spanish flu or the current COVID-19 pandemic caused by the coronavirus SARS-CoV-2. Nevertheless, it is clear that we could not live in a world without these tiny beings. Endogenous retroviruses have been key to our evolution and for the regulation of gene expression, and the gut microbiota helps us digest compounds that we could not otherwise process. In addition, we have used microorganisms to preserve or prepare food for millennia and more recently to obtain drugs such as antibiotics or to develop recombinant DNA technologies. Due to the enormous importance of microorganisms for our survival, they have significantly influenced the population genetics of different human groups. This paper will review the role of microorganisms as "villains" who have been responsible for tremendous mortality throughout history but also as "friends" who help us survive and evolve.

Pathology of lung-specific thrombosis and inflammation in COVID-19

BACKGROUND

Infection by SARS-CoV-2 produces significant pulmonary pathology including endothelial damage with resultant thrombotic events. While pathologic features were described, there are limited data on the relationship of these changes to the inflammatory response and the production of thromboses.

OBJECTIVE

To investigate pathology of COVID-19-related immunothrombosis.

PATIENTS/METHODS

Tissue samples from lung, kidney, brain and heart that were collected from 45 patients who died of COVID-19. Histopathological examination was performed after H&E and Picro-Mallory staining in combination with (immuno)fluorescence to visualize neutrophil extracellular traps. Ultrastructural alterations in lungs were studied with scanning and transmission electron microscopy.

RESULTS

Inflammatory changes and thrombosis were substantially more pronounced in the lung than in the kidney, heart, and brain. The most common pathologic finding was diffuse alveolar damage. In addition, most lung samples showed thrombi in vessels. The cause of death in single cases was massive pulmonary embolism. Ultrastructural examination revealed neutrophils attached to endothelium, perhaps as a step towards transendothelial migration. In addition, platelets were identified in the midst of fibrin as individual procoagulant balloon-like cells. Ultrastructural examination demonstrated numerous virion-like particles.

CONCLUSIONS

Studying (ultra)structural features of the autopsy lung samples from patients with COVID-19 has provided evidence for a pathogenic link between inflammation and thrombosis. The major features in the lungs of COVID-19 patients comprised primary inflammatory thrombosis associated with diffuse alveolar damage. The lungs had pronounced circulatory changes with inflammation-dependent intravascular blood clotting, whereas heart, brain, and kidneys had predominantly degenerative changes that were distinct from the lung pathology.

PGRMC1 Exerts Its Function of Anti-Influenza Virus in the Central Nervous System

The influenza A virus (IAV) infection is usually restricted to the respiratory tract and only rarely enters the central nervous system (CNS) and causes neurological symptoms. However, the roles of host factors involved in IAV infection in the CNS remain largely undetermined. Therefore, we aimed to characterize the host responses to IAV infection in the brain. We isolated a strain of IAV H5N6, which is neurotoxic and highly pathogenic to mice. High-throughput RNA sequencing (RNA-seq) revealed 240 differentially expressed genes in IAV-infected brains. Among the significantly downregulated genes, we focused on the gene encoding progesterone receptor membrane component-1 (PGRMC1) and observed that IAV H5N6 infection clearly inhibited PGRMC1 in both neuroblastoma and glioma cells. Furthermore, treatment with AG205, a PGRMC1-specific inhibitor, or PGRMC1 knockout promoted H5N6 multiplication in vitro, while overexpression of PGRMC1 resulted in opposite effects. Furthermore, AG205 treatment or PGRMC1 knockout significantly inhibited the retinoic acid-inducible gene I (RIG-I)-mediated interferon beta (IFN-β) signaling pathway and reduced the levels of several antiviral proteins (Mx1 and ISG15). In addition, PGRMC1-mediated regulation of IFN signaling relied on inhibition of the expression and ubiquitination of RIG-I. The loss of PGRMC1 leads to an increased susceptibility of mice (brain and lung) to influenza A virus infection. Conclusively, our results show for the first time that IAV H5N6 downregulates PGRMC1 expression to contribute to virus proliferation by inhibiting RIG-I-mediated IFN-β production in the brain. These findings may offer new insights regarding the interplay between IAV and host factors that may impact IAV pathogenicity in the brain.

IMPORTANCE Central nervous system (CNS) disease is one of the most common extra-respiratory tract complications of influenza A virus (IAV) infections. However, there is still little knowledge about IAV regulating host responses in brain. In this study, we identified progesterone receptor membrane component-1 (PGRMC1) as a novel host factor involved in the replication and propagation of IAV H5N6 in the host brain. We also observed that PGRMC1 antagonism was required for viral evasion from the host immune response during IAV infection via inhibition of the retinoic acid-inducible gene I (RIG-I)-mediated interferon beta (IFN-β) signaling pathway and downstream antiviral gene expression. This study revealed a newly identified regulatory mechanism used by IAV H5N6 to ensure its life cycle in the CNS.

Molecular archeology of human viruses

The evolution of human-virus associations is usually reconstructed from contemporary patterns of genomic diversity. An intriguing, though still rarely implemented, alternative is to search for the genetic material of viruses in archeological and medical archive specimens to document evolution as it happened. In this chapter, we present lessons from ancient DNA research and incorporate insights from virology to explore the potential range of applications and likely limitations of archeovirological approaches. We also highlight the numerous questions archeovirology will hopefully allow us to tackle in the near future, and the main expected roadblocks to these avenues of research.

In quest of small-molecules as potent non-competitive inhibitors against influenza

A series of scaffolds namely aurones, 3-indolinones, 4-quinolones and cinnamic acid-piperazine hybrids, was designed, synthesized and investigated in vitro against influenza A/H1N1pdm09 virus. Designed molecules adopted different binding mode i.e., in 430-cavity of neuraminidase, unlike sialic acid and oseltamivir in molecular docking studies. All molecules reduced the viral titer and exhibited non-cytotoxicity along with cryo-protective property towards MDCK cells. Molecules (Z)-2-(3'-Chloro-benzylidene)-1,2-dihydro-indol-3-one (2f), (Z)-2-(4'-Chloro-benzylidene)-1,2-dihydro-indol-3-one (2g) and 2-(2'-Methoxy-phenyl)-1H-quinolin-4-one (3a) were the most interesting molecules identified in this research, endowed with robust potencies showing low-nanomolar EC₅₀ values of 4.0 nM, 6.7 nM and 4.9 nM, respectively, compared to reference competitive and non-competitive inhibitors: oseltamivir (EC₅₀ = 12.7 nM) and quercetin (EC₅₀ = 0.56 µM), respectively. Besides, 2f, 2g and 3a exhibited good neuraminidase inhibitory activity in sub-micromolar range (IC₅₀ = 0.52 µM, 3.5 µM, 1.3 µM respectively). Moreover, these molecules were determined as non-competitive inhibitors similar to reference non-competitive inhibitor quercetin unlike reference competitive inhibitor oseltamivir in kinetics studies.

Intra-species sialic acid polymorphism in humans: a common niche for influenza and coronavirus pandemics?

The ongoing COVID-19 pandemic has led to more than 159 million confirmed cases with over 3.3 million deaths worldwide, but it remains mystery why most infected individuals (∼98%) were asymptomatic or only experienced mild illness. The same mystery applies to the deadly 1918 H1N1 influenza pandemic, which has puzzled the field for a century. Here we discuss dual potential properties of the 1918 H1N1 pandemic viruses that led to the high fatality rate in the small portion of severe cases, while about 98% infected persons in the United States were self-limited with mild symptoms, or even asymptomatic. These variations now have been postulated to be impacted by polymorphisms of the sialic acid receptors in the general population. Since coronaviruses (CoVs) also recognize sialic acid receptors and cause severe acute respiratory syndrome epidemics and pandemics, similar principles of influenza virus evolution and pandemicity may also apply to CoVs. A potential common principle of pathogen/host co-evolution of influenza and CoVs under selection of host sialic acids in parallel with different epidemic and pandemic influenza and coronaviruses is discussed.

Autopsy findings in COVID-19-related deaths: a literature review

Although many clinical reports have been published, little is known about the pathological post-mortem findings from people who have died of the novel coronavirus disease. The need for postmortem information is urgent to improve patient management of mild and severe illness, and treatment strategies. The present systematic review was carried out according to the Preferred Reporting Items for Systematic Review (PRISMA) standards. A systematic literature search and a critical review of the collected studies were conducted. An electronic search of PubMed, Science Direct Scopus, Google Scholar, and Excerpta Medica Database (EMBASE) from database inception to June 2020 was performed. We found 28 scientific papers; the total amount of cases is 341. The major histological feature in the lung is diffuse alveolar damage with hyaline membrane formation, alongside microthrombi in small pulmonary vessels. It appears that there is a high incidence of deep vein thrombosis and pulmonary embolism among COVID-19 decedents, suggesting endothelial involvement, but more studies are needed. A uniform COVID-19 post-mortem diagnostic protocol has not yet been developed. In a time in which international collaboration is essential, standardized diagnostic criteria are fundamental requirements.

A Centenary Tale of Two Pandemics: The 1918 Influenza Pandemic and COVID-19, Part I

Separated by a century, the influenza pandemic of 1918 and the COVID-19 pandemic of 2019-2021 are among the most disastrous infectious disease emergences of modern times. Although caused by unrelated viruses, the two pandemics are nevertheless similar in their clinical, pathological, and epidemiological features, and in the civic, public health, and medical responses to combat them. Comparing and contrasting the two pandemics, we consider what lessons we have learned over the span of a century and how we are applying those lessons to the challenges of COVID-19.

A series of COVID-19 autopsies with clinical and pathologic comparisons to both seasonal and pandemic influenza

Autopsies of patients who have died from COVID‐19 have been crucial in delineating patterns of injury associated with SARS‐CoV‐2 infection. Despite their utility, comprehensive autopsy studies are somewhat lacking relative to the global burden of disease, and very few comprehensive studies contextualize the findings to other fatal viral infections. We developed a novel autopsy protocol in order to perform postmortem examinations on victims of COVID‐19 and herein describe detailed clinical information, gross findings, and histologic features observed in the first 16 complete COVID‐19 autopsies. We also critically evaluated the role of ancillary studies used to establish a diagnosis of COVID‐19 at autopsy, including immunohistochemistry (IHC), in situ hybridization (ISH), and electron microscopy (EM). IHC and ISH targeting SARS‐CoV‐2 were comparable in terms of the location and number of infected cells in lung tissue; however, nonspecific staining of bacteria was seen occasionally with IHC. EM was unrevealing in blindly sampled tissues. We then compared the clinical and histologic features present in this series to six archival cases of fatal seasonal influenza and six archival cases of pandemic influenza from the fourth wave of the ‘Spanish Flu’ in the winter of 1920. In addition to routine histology, the inflammatory infiltrates in the lungs of COVID‐19 and seasonal influenza victims were compared using quantitative IHC. Our results demonstrate that the clinical and histologic features of COVID‐19 are similar to those seen in fatal cases of influenza, and the two diseases tend to overlap histologically. There was no significant difference in the composition of the inflammatory infiltrate in COVID‐19 and influenza at sites of acute lung injury at the time of autopsy. Our study underscores the relatively nonspecific clinical features and pathologic changes shared between severe cases of COVID‐19 and influenza, while also providing important caveats to ancillary methods of viral detection.

Antimicrobial Resistance Threats in the emerging COVID-19 pandemic: Where do we stand?

Antimicrobial resistance (AMR) continues to exert a substantial toll on the global health and world economy and is now expected to be hidden by COVID-19 for a while. The wrong consumption of antibiotics during the COVID-19 pandemic will raise disastrous effects on AMR management and antibiotic stewardship programs. This is related to the concerns extrapolated due to an increase in mortality rates in patients with bacterial coinfections. Importantly, the immune system of COVID-19 patients in regions with high AMR may be fighting on two fronts altogether, the virus and MDR bacteria. Current control policies to manage AMR and prioritization of antibiotic stewardship plans are mandatory during this pandemic. This review aims to discuss the rising concerns of the excess use of antibiotics in COVID-19 patients highlighting the role of bacterial coinfections in these patients. Types of prescribed antibiotics and the development of antibiotic resistance is addressed as well.

Autopsies in pandemics - a perspective on barriers and benefits. Is it time for a revival?

Influenza virus and coronavirus pandemics regularly sweep the globe, at great cost of health and economy. Our aim was to conduct a PubMed search for autopsy studies on influenza and coronavirus to investigate the contribution of autopsies during pandemics, focussing on autopsy methods and procedures and the role of autopsy findings in pandemics. The retrieved autopsy studies generally relied on microscopy, polymerase chain reaction (PCR), immunostaining and electron microscopy. Most were small and reported on lung effects, including diffuse alveolar damage (DAD), pneumonia and tracheobronchitis. Antibiotic therapy has diminished a role for bacterial pneumonia, whereas obesity is an emerging risk factor. Autopsy studies have provided new insights into coronavirus disease 2019 (COVID‐19) treatments like anti‐coagulative therapy. Unfortunately, autopsies during pandemics are hampered by lack of guidelines, facilities and expertise for handling potentially infectious corpses and by widely varying recommendations for personal protective equipment and procedures. The Department of Forensic Pathology, at the Forensic Institute, at the University of Copenhagen in Denmark has, in collaboration with the Department of Pathology, Rigshospitalet, Copenhagen, initiated a prospective observational study on COVID‐19‐related deaths encompassing postmortem imaging, standardized autopsy procedures/reporting and extensive tissue sampling for histological, chemical, microbiological and genetic analysis. The study involves a diverse array of research groups at the University of Copenhagen, and the clinical field.

Postmortem Stability of SARS-CoV-2 in Nasopharyngeal Mucosa

Analyses of infection chains have demonstrated that severe acute respiratory syndrome coronavirus 2 is highly transmissive. However, data on postmortem stability and infectivity are lacking. Our finding of nasopharyngeal viral RNA stability in 79 corpses showed no time-dependent decrease. Maintained infectivity is supported by virus isolation up to 35 hours postmortem.

Viruses as 'Truffle Hounds': Molecular Tools for Untangling Brain Cellular Pathology

The ability of viruses to evolve several orders of magnitude faster than their host cells has enabled them to exploit host cellular machinery by selectively recruiting multiprotein complexes (MPCs) for their catalyzed assembly and replication. This hijacking may depend on alternative, 'moonlighting' functions of host proteins that deviate from their canonical functions thereby inducing cellular pathology. Here, we posit that if virus-induced cellular pathology is similar to that of other, unknown (non-viral) causes, the identification and molecular characterization of the host proteins involved in virus-mediated cellular pathology can be leveraged to decipher the non-viral disease-relevant mechanisms. We focus on how virus-induced aberrant proteostasis and protein aggregation resemble the cellular pathology of sporadic neurodegenerative diseases (NDs) and how this can be exploited for drug discovery.

Effect of early oseltamivir on outpatients without hypoxia with suspected COVID-19

Background

Since December 2019 coronavirus disease 2019 (COVID-19) outbreaks have occurred in China and many countries around the world. The effectiveness of oseltamivir on COVID-19 suspected outpatients without hypoxia was evaluated.

Methods

A total of 16 COVID-19 suspected medical personnel and their cohabitation families without hypoxia, who came to the adult fever clinic from March to June 2020 were studied. All patients received antiviral therapy (oseltamivir) and antibacterial therapy together.

Results

Most of the infected patients were female (10, 63%), 1 had diabetes (6%) and 3 hypertension (19%). The median age was 45 years (interquartile range [IQR] 31–60 years). Oseltamivir administration made the temperature fall within 24 h in part (10, 63%). Clinical data were compared between patients receiving early treatment (ET) with oseltamivir, initiated within 24 h, and patients administered late treatment (LT), initiated after this time point. Duration of fever was shorter in the ET group than in the LT group (31 ± 21 h versus 94 ± 38 h; p < 0.001). The time from fever onset to treatment initiation correlated with duration of fever (r = 0.77; p < 0.001) and the time from peak to decline (r = 0.58; p < 0.05).

Conclusion

These findings suggest that early oseltamivir administration may lower the duration of fever in COVID-19 suspected outpatients without hypoxia when it is used in combination with antibacterial therapy.

Adaptation of influenza viruses to human airway receptors

Through annual epidemics and global pandemics, influenza A viruses (IAVs) remain a significant threat to human health as the leading cause of severe respiratory disease. Within the last century, four global pandemics have resulted from the introduction of novel IAVs into humans, with components of each originating from avian viruses. IAVs infect many avian species wherein they maintain a diverse natural reservoir, posing a risk to humans through the occasional emergence of novel strains with enhanced zoonotic potential. One natural barrier for transmission of avian IAVs into humans is the specificity of the receptor-binding protein, hemagglutinin (HA), which recognizes sialic-acid-containing glycans on host cells. HAs from human IAVs exhibit “human-type” receptor specificity, binding exclusively to glycans on cells lining the human airway where terminal sialic acids are attached in the α2-6 configuration (NeuAcα2-6Gal). In contrast, HAs from avian viruses exhibit specificity for “avian-type” α2-3-linked (NeuAcα2-3Gal) receptors and thus require adaptive mutations to bind human-type receptors. Since all human IAV pandemics can be traced to avian origins, there remains ever-present concern over emerging IAVs with human-adaptive potential that might lead to the next pandemic. This concern has been brought into focus through emergence of SARS-CoV-2, aligning both scientific and public attention to the threat of novel respiratory viruses from animal sources. In this review, we summarize receptor-binding adaptations underlying the emergence of all prior IAV pandemics in humans, maintenance and evolution of human-type receptor specificity in subsequent seasonal IAVs, and potential for future human-type receptor adaptation in novel avian HAs.

Higher prevalence of pulmonary macrothrombi in SARS-CoV-2 than in influenza A: autopsy results from 'Spanish flu' 1918/1919 in Switzerland to Coronavirus disease 2019

Similar to the influenza A pandemic in 1918/1919, the new Coronavirus disease 2019 (COVID‐19) has spread globally. The causes of death in COVID‐19 are frequently compared to a seasonal influenza outbreak. Complete COVID‐19 autopsy studies were almost non‐existent in the first months of the outbreak and are still rare with respect to the number of deaths. It has been recently reported that capillary microthrombi are significantly more prevalent in patients with COVID‐19 than in patients with influenza A. To date, the contribution of macrothrombi, i.e. visible thrombi in pulmonary arteries, to the death of patients with influenza A in comparison to COVID‐19 remains unaddressed. Here, we report autopsy findings in 411 patients who died from the ‘Spanish’ influenza A pandemic between May 1918 and April 1919 at the University Hospital Zurich, Switzerland. We compare these results with influenza A autopsies from 2009 to 2020, other influenza A autopsy series and all COVID‐19 autopsies published to date. No descriptions of any macroscopic thromboembolic events were mentioned in influenza A autopsy reports. In 75 published COVID‐19 autopsies, pulmonary artery thrombosis/embolism was reported in 36%. The direct comparison of macroscopic autopsy findings suggests a significantly greater degree of grossly visible pulmonary macrothrombi in patients with COVID‐19 in comparison to influenza A autopsies even though most patients received empiric thromboprophylaxis. This is consistent with the concept of a SARS‐related de novo coagulopathy with generalised in situ clot formation, which could explain the high incidence of pulmonary thrombosis/embolism with or without underlying deep vein thrombosis and in the absence of a history of venous thromboembolic events.

Insights into pathogenesis of fatal COVID-19 pneumonia from histopathology with immunohistochemical and viral RNA studies

Introduction

We describe post‐mortem pulmonary histopathologic findings of COVID‐19 pneumonia in patients with a spectrum of disease course, from rapid demise to prolonged hospitalisation.

Methods and results

Histopathologic findings in post‐mortem lung tissue from eight patients who died from COVID‐19 pneumonia were reviewed. Immunohistochemistry (IHC) and next‐generation sequencing (NGS) were performed to detect virus. Diffuse alveolar damage (DAD) was seen in all cases with a spectrum of acute phase and/or organising phase. IHC with monoclonal antibodies against SARS‐CoV‐2 viral nucleoprotein and spike protein detected virus in areas of acute but not organising DAD, with intracellular viral antigen and RNA expression seen predominantly in patients with duration of illness less than 10 days. Major vascular findings included thrombi in medium‐ and large‐calibre vessels, platelet microthrombi detected by CD61 IHC and fibrin microthrombi.

Conclusions

Presence of SARS‐CoV‐2 viral RNA by NGS early in the disease course and expression of viral antigen by IHC exclusively in the acute, but not in the organising phase of DAD, suggests that the virus may play a major role in initiating the acute lung injury of DAD, but when DAD progresses to the organising phase the virus may have been cleared from the lung by the patient's immune response. These findings suggest the possibility of a major change during the disease course of COVID‐19 pneumonia that may have therapeutic implications. Frequent thrombi and microthrombi may also present potential targets for therapeutic intervention.

The 1918 Influenza Pandemic and Its Legacy

Just over a century ago in 1918-1919, the "Spanish" influenza pandemic appeared nearly simultaneously around the world and caused extraordinary mortality-estimated at 50-100 million fatalities-associated with unexpected clinical and epidemiological features. The pandemic's sudden appearance and high fatality rate were unprecedented, and 100 years later still serve as a stark reminder of the continual threat influenza poses. Sequencing and reconstruction of the 1918 virus have allowed scientists to answer many questions about its origin and pathogenicity, although many questions remain. Several of the unusual features of the 1918-1919 pandemic, including age-specific mortality patterns and the high frequency of severe pneumonias, are still not fully understood. The 1918 pandemic virus initiated a pandemic era still ongoing. The descendants of the 1918 virus remain today as annually circulating and evolving influenza viruses causing significant mortality each year. This review summarizes key findings and unanswered questions about this deadliest of human events.

Incidence and Risk Factors of Deep Vein Thrombosis in Hospitalized COVID-19 Patients

Deep vein thrombosis (DVT) is prevalent in patients with coronavirus disease 2019 (COVID-19). However, the risk factors and incidence rate of DVT remains elusive. Here, we aimed to assess the incidence rate and risk factors of DVT. All patients diagnosed with COVID-19 and performed venous ultrasound by ultrasound deparment between December 2019 and April 2020 in Wuhan Jin Yin-tan hospital were enrolled. Demographic information and clinical features were retrospectively collected. Notably, a comparison between the DVT and the non-DVT groups was explored. The incidence rate of venous thrombosis was 35.2% (50 patients out of 142). Moreover, the location of thrombus at the proximal extremity veins was 5.6% (n = 8), while at distal extremity veins was 35.2% (n = 50) of the patients. We also noted that patients with DVT exhibited a high level of D-dimer (OR 10.9 (95% CI, 3.3-36.0), P < 0.001), were admitted to the intensive care unit (OR 6.5 (95% CI, 2.1-20.3), P = 0.001), a lower usage of the anticoagulant drugs (OR 3.0 (95% CI, 1.1-7.8), P < 0.001). Finally, this study revealed that a high number of patients with COVID-19 developed DVT. This was observed particularly in critically ill patients with high D-dimer levels who required no anticoagulant medication.

Normal Respiratory Flora as a Cause of Community-Acquired Pneumonia

Background

Intensive studies have failed to identify an etiologic agent in >50% cases of community-acquired pneumonia (CAP). Bacterial pneumonia follows aspiration of recognized bacterial pathogens (RBPs) such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus after they have colonize the nasopharynx. We hypothesized that aspiration of normal respiratory flora (NRF) might also cause CAP.

Methods

We studied 120 patients hospitalized for CAP who provided a high-quality sputum specimen at, or soon after admission, using Gram stain, quantitative sputum culture, bacterial speciation by matrix-assisted laser desorption ionization time-of-flight, and viral polymerase chain reaction. Thresholds for diagnosis of bacterial infection were ≥10⁵ colony-forming units (cfu)/mL sputum for RBPs and ≥10⁶ cfu for NRF.

Results

Recognized bacterial pathogens were found in 68 of 120 (56.7%) patients; 14 (20.1%) of these had a coinfecting respiratory virus. Normal respiratory flora were found in 31 (25.8%) patients; 10 (32.2%) had a coinfecting respiratory virus. Infection by ≥2 RBPs occurred in 10 cases and by NRF together with RBPs in 13 cases. Among NRF, organisms identified as Streptococcus mitis, which share many genetic features of S pneumoniae, predominated. A respiratory virus alone was found in 16 of 120 (13.3%) patients. Overall, an etiologic diagnosis was established in 95.8% of cases.

Conclusions

Normal respiratory flora, with or without viral coinfection, appear to have caused one quarter of cases of CAP and may have played a contributory role in an additional 10.8% of cases caused by RBPs. An etiology for CAP was identified in >95% of patients who provided a high-quality sputum at, or soon after, the time of admission.

The Effect of Influenza Virus on the Human Oropharyngeal Microbiome

Background

Secondary bacterial infections are an important cause of morbidity and mortality associated with influenza infections. As bacterial disease can be caused by a disturbance of the host microbiome, we examined the impact of influenza on the upper respiratory tract microbiome in a human challenge study.

Methods

The dynamics and ecology of the throat microbiome were examined following an experimental influenza challenge of 52 previously-healthy adult volunteers with influenza A/Wisconsin/67/2005 (H3N2) by intranasal inoculation; 35 healthy control subjects were not subjected to the viral challenge. Serial oropharyngeal samples were taken over a 30-day period, and the V1-V3 region of the bacterial 16S ribosomal RNA sequences were amplified and sequenced to determine the composition of the microbiome. The carriage of pathogens was also detected.

Results

Of the 52 challenged individuals, 43 developed proven influenza infections, 33 of whom became symptomatic. None of the controls developed influenza, although 22% reported symptoms. The diversity of bacterial communities remained remarkably stable following the acquisition of influenza, with no significant differences over time between individuals with influenza and those in the control group. Influenza infection was not associated with perturbation of the microbiome at the level of phylum or genus. There was no change in colonization rates with Streptococcus pneumoniae or Neisseria meningitidis.

Conclusions

The throat microbiota is resilient to influenza infection, indicating the robustness of the upper-airway microbiome.

Feasibility of postmortem examination in the era of COVID-19 pandemic: the experience of a Northeast Italy University Hospital

With the continuous spreading of SARS-CoV-2 and increasing number of deaths worldwide, the need and appropriateness for autopsy in patients with COVID-19 became a matter of discussion. In fact, in the COVID-19 era protection of healthcare workers is a priority besides patient management. No evidence is currently available about the real risk related to the procedure as well as to the subsequent management of the samples. We herein describe the procedure that has been used to perform the first series of postmortem examinations in the COVID center of the Padua University Hospital, Padua, Italy, after the implementation of an ad hoc operating procedure, to minimize the risk of infection for pathologists and technicians. Provided that the procedure is performed in an adequate environment respecting strict biosafety rules, our data indicate that complete postmortem examination appears to be safe and will be highly informative providing useful insights into the complex disease pathogenesis.

Influenza-associated aspergillosis in critically-ill patients-a retrospective bicentric cohort study

Influenza was recently reported as a risk factor for invasive aspergillosis (IA). We aimed to describe prognostic factors for influenza-associated IA (IAA) and poor outcome and mortality in critically ill patients in Switzerland. All adults with confirmed influenza admitted to the ICU at two Swiss tertiary care centres during the 2017/2018 influenza season were retrospectively evaluated. IAA was defined by clinical, mycological and radiological criteria: a positive galactomannan in bronchoalveolar lavage or histopathological or cultural evidence in respiratory specimens of Aspergillus spp., any radiological infiltrate and a compatible clinical presentation. Poor outcome was defined as a composite of in-hospital mortality, ICU length of stay (LOS), invasive ventilation for > 7 days or extracorporeal membrane oxygenation. Of 81 patients with influenza in the ICU, 9 (11%) were diagnosed with IAA. All patients with IAA had poor outcome compared to 26 (36%) patients without IAA (p < 0.001). Median ICU-LOS and mortality were 17 vs. 3 days (p < 0.01) and 3/9 (33%) vs. 13/72 (18%; p = 0.37) in patients with vs. without IAA, respectively. Patients with IAA had significantly longer durations of antibiotic therapy, vasoactive support and mechanical ventilation. Aspergillus was the most common respiratory co-pathogen (9/40, 22%) followed by classical bacterial co-pathogens. IAA was not associated with classical risk factors. Aspergillus is a common superinfection in critically ill influenza patients associated with poor outcome and longer duration of organ supportive therapies. Given the absence of classical risk factors for aspergillosis, greater awareness is necessary, particularly in those requiring organ supportive therapies.

Making Universal Influenza Vaccines: Lessons From the 1918 Pandemic

The year 2018 marked the 100th anniversary of the deadliest event in human history. In 1918-1919, pandemic influenza spread globally and caused an estimated 50-100 million deaths associated with unexpected clinical and epidemiological features. The descendants of the 1918 virus continue to circulate as annual epidemic viruses causing significant mortality each year. The 1918 influenza pandemic serves as a benchmark for the development of universal influenza vaccines. Challenges to producing a truly universal influenza vaccine include eliciting broad protection against antigenically different influenza viruses that can prevent or significantly downregulate viral replication and reduce morbidity by preventing development of viral and secondary bacterial pneumonia. Perhaps the most important goal of such vaccines is not to prevent influenza, but to prevent influenza deaths.

Truth and transparency in a time of crisis

Lessons from history underline the importance of having direct lines of communication to and from public health officials, who must remain free from policital bias in times of crisis.

Super-dominant pathobiontic bacteria in the nasopharyngeal microbiota as causative agents of secondary bacterial infection in influenza patients

The source of secondary lower respiratory tract bacterial infections in influenza patients is not fully understood. A case–control study was conducted during the 2017–2018 influenza epidemic period in Beijing, China. Nasopharyngeal swabs were collected from 52 virologically confirmed influenza patients and 24 healthy medical staff. The nasopharyngeal microbiota taxonomic composition was analysed using high-throughput sequencing of the 16S rRNA gene V3–V4 regions. The super-dominant pathobiontic bacterial genus (SDPG) was defined as that accounting for >50% of sequences in a nasopharyngeal swab. We attempted to isolate bacteria of this genus from both nasopharyngeal swabs and lower-respiratory tract samples and analyse their genetic similarities. We observed a significantly lower taxonomy richness in influenza cases compared with healthy controls. A SDPG was detected in 61% of severe cases but in only 24% of mild cases and 29% of healthy controls. In 10 cases, the species isolated from lower-respiratory tract infection sites were identified as belonging to the nasopharyngeal microbiota SDPG. Genetically identical strains were isolated from both nasopharyngeal swabs and lower-respiratory tract infection sites, including 23 Acinetobacter baumannii strains from six severe cases, six Klebsiella pneumoniae strains from two severe cases, five Pseudomonas aeruginosa strains from one severe and one mild case, and four Corynebacterium striatum strains from two severe cases. The SDPG in the nasopharyngeal microbiota are the likely cause of subsequent infection in influenza patients.

Disruption of cellular proteostasis by H1N1 influenza A virus causes α-synuclein aggregation

Neurodegenerative diseases feature specific misfolded or misassembled proteins associated with neurotoxicity. The precise mechanisms by which protein aggregates first arise in the majority of sporadic cases have remained unclear. Likely, a first critical mass of misfolded proteins starts a vicious cycle of a prion-like expansion. We hypothesize that viruses, having evolved to hijack the host cellular machinery for catalyzing their replication, lead to profound disturbances of cellular proteostasis, resulting in such a critical mass of protein aggregates. Here, we investigated the effect of influenza virus (H1N1) strains on proteostasis of proteins associated with neurodegenerative diseases in Lund human mesencephalic dopaminergic cells in vitro and infection of Rag knockout mice in vivo. We demonstrate that acute H1N1 infection leads to the formation of α-synuclein and Disrupted-in-Schizophrenia 1 (DISC1) aggregates, but not of tau or TDP-43 aggregates, indicating a selective effect on proteostasis. Oseltamivir phosphate, an antiinfluenza drug, prevented H1N1-induced α-synuclein aggregation. As a cell pathobiological mechanism, we identified H1N1-induced blocking of autophagosome formation and inhibition of autophagic flux. In addition, α-synuclein aggregates appeared in infected cell populations connected to the olfactory bulbs following intranasal instillation of H1N1 in Rag knockout mice. We propose that H1N1 virus replication in neuronal cells can induce seeds of aggregated α-synuclein or DISC1 that may be able to initiate further detrimental downstream events and should thus be considered a risk factor in the pathogenesis of synucleinopathies or a subset of mental disorders. More generally, aberrant proteostasis induced by viruses may be an underappreciated factor in initiating protein misfolding.

Profiling natural serum antibodies of non-human primates with a carbohydrate antigen microarray

BACKGROUND

Engineering of α-Galactosyltransferase gene-knockout pigs circumvented hyperacute rejection of pig organs after xenotransplantation in non-human primates. Overcoming this hurdle revealed the importance of non-α-Gal carbohydrate antigens in the immunobiology of acute humoral xenograft rejection.

METHODS

This study analyzed serum from seven naïve cynomolgus monkeys (blood type O/B/AB = 3/2/2) for the intensity of natural IgM and IgG signals using carbohydrate antigen microarray, which included historically reported α-Gal and non-α-Gal carbohydrate antigens with various modifications.

RESULTS

The median (range) of IgM and IgG signals were 12.71 (7.23-16.38) and 9.05 (7.23-15.90), respectively. The highest IgM and IgG signals with narrowest distribution were from mono- and disaccharides, followed by modified structures. Natural anti-α-Gal antibody signals were medium to high in IgM (11.2-15.9) and medium in IgG (8.5-11.6) spectra, and was highest with Lac core structure (Galα1-3Galβ1-4Glc, iGb3) and lowest with LacNAc core structure (Galα1-3Galβ1-4GlcNAc). Similar signal intensities (up to 15.8 in IgM and up to 11.8 in IgG) were observed for historically detected natural non-α-Gal antigens, which included Tn antigen, T antigen, GM2 glycolipid, and Sd^a antigen. The hierarchical clustering analysis revealed the presence of clusters of anti-A antibodies and was capable of distinguishing between the blood group B and AB non-human primates.

CONCLUSIONS

The results presented here provide the most comprehensive evaluation of natural antibodies present in cynomolgus monkeys.

The 1918 influenza pandemic: 100 years of questions answered and unanswered

The 2018-2019 period marks the centennial of the "Spanish" influenza pandemic, which caused at least 50 million deaths worldwide. The unprecedented nature of the pandemic's sudden appearance and high fatality rate serve as a stark reminder of the threat influenza poses. Unusual features of the 1918-1919 pandemic, including age-specific mortality and the high frequency of severe pneumonias, are still not fully understood. Sequencing and reconstruction of the 1918 virus has allowed scientists to answer many questions about its origin and pathogenicity, although many questions remain. This Review summarizes key findings and still-to-be answered questions about this deadliest of human events.

1918 H1N1 Influenza Virus Replicates and Induces Proinflammatory Cytokine Responses in Extrarespiratory Tissues of Ferrets

Background

The 1918 Spanish H1N1 influenza pandemic was the most severe recorded influenza pandemic with an estimated 20-50 million deaths worldwide. Even though it is known that influenza viruses can cause extrarespiratory tract complications-which are often severe or even fatal-the potential contribution of extrarespiratory tissues to the pathogenesis of 1918 H1N1 virus infection has not been studied comprehensively.

Methods

Here, we performed a time-course study in ferrets inoculated intranasally with 1918 H1N1 influenza virus, with special emphasis on the involvement of extrarespiratory tissues. Respiratory and extrarespiratory tissues were collected after inoculation for virological, histological, and immunological analysis.

Results

Infectious virus was detected at high titers in respiratory tissues and, at lower titers in most extrarespiratory tissues. Evidence for active virus replication, as indicated by the detection of nucleoprotein by immunohistochemistry, was observed in the respiratory tract, peripheral and central nervous system, and liver. Proinflammatory cytokines were up-regulated in respiratory tissues, olfactory bulb, spinal cord, liver, heart, and pancreas.

Conclusions

1918 H1N1 virus spread to and induced cytokine responses in tissues outside the respiratory tract, which likely contributed to the severity of infection. Moreover, our data support the suggested link between 1918 H1N1 infection and central nervous system disease.

Host-Pathogen Interactions in Gram-Positive Bacterial Pneumonia

Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality worldwide. Despite broad literature including basic and translational scientific studies, many gaps in our understanding of host-pathogen interactions remain. In this review, pathogen virulence factors that drive lung infection and injury are discussed in relation to their associated host immune pathways. CAP epidemiology is considered, with a focus on Staphylococcus aureus and Streptococcus pneumoniae as primary pathogens. Bacterial factors involved in nasal colonization and subsequent virulence are illuminated. A particular emphasis is placed on bacterial pore-forming toxins, host cell death, and inflammasome activation. Identified host-pathogen interactions are then examined by linking pathogen factors to aberrant host response pathways in the context of acute lung injury in both primary and secondary infection. While much is known regarding bacterial virulence and host immune responses, CAP management is still limited to mostly supportive care. It is likely that improvements in therapy will be derived from combinatorial targeting of both pathogen virulence factors and host immunomodulation.

A year of terror and a century of reflection: perspectives on the great influenza pandemic of 1918-1919

Background

In the spring of 1918, the “War to End All Wars”, which would ultimately claim more than 37 million lives, had entered into its final year and would change the global political and economic landscape forever. At the same time, a new global threat was emerging and would become one of the most devastating global health crises in recorded history.

Main text

The 1918 H1N1 pandemic virus spread across Europe, North America, and Asia over a 12-month period resulting in an estimated 500 million infections and 50–100 million deaths worldwide, of which ~ 50% of these occurred within the fall of 1918 (Emerg Infect Dis 12:15-22, 2006, Bull Hist Med 76:105-115, 2002). However, the molecular factors that contributed to the emergence of, and subsequent public health catastrophe associated with, the 1918 pandemic virus remained largely unknown until 2005, when the characterization of the reconstructed pandemic virus was announced heralding a new era of advanced molecular investigations (Science 310:77-80, 2005). In the century following the emergence of the 1918 pandemic virus we have landed on the Moon, developed the electronic computer (and a global internet), and have eradicated smallpox. In contrast, we have a largely remedial knowledge and understanding of one of the greatest scourges in recorded history.

Conclusion

Here, we reflect on the 1918 influenza pandemic, including its emergence and subsequent rapid global spread. In addition, we discuss the pathophysiology associated with the 1918 virus and its predilection for the young and healthy, the rise of influenza therapeutic research following the pandemic, and, finally, our level of preparedness for future pandemics.

The origins of the great pandemic

The timing and location of the first cases of the 1918 influenza pandemic are still controversial, a century after the pandemic became widely recognized. Here, we critically review competing hypotheses on the timing and geographical origin of this important outbreak and provide new historical insights into debates within military circles as to the nature of putative pre-1918 influenza activity. We also synthesize current knowledge about why the 1918 pandemic was so intense in young adults. Although it is still not clear precisely when and where the outbreak began and symptom-based reports are unlikely to reveal the answer, indirect methods including phylogenetics provide important clues, and we consider whether intense influenza activity as far back as 1915 in the USA may have been caused by viral strains closely related to the 1918 one.

The Importance of the Autopsy in Medicine: Perspectives of Pathology Colleagues

This article presents a perspective on the importance of the autopsy in medical practice and science based on experiences of the authors as physician-scientists involved in autopsy practice. Our perspectives are presented on the seminal contributions of the autopsy in the areas of cardiovascular disease, including congenital heart disease, atherosclerosis, coronary artery disease, and myocardial infarction, and infectious disease, including tuberculosis and viral infections. On the positive side of the future of the autopsy, we discuss the tremendous opportunities for important research to be done by application of advanced molecular biological techniques to formalin-fixed, paraffin-embedded tissue blocks obtained at autopsy. We also note with concern the countervailing forces impacting the influence of pathology in education and clinical practice at our academic medical centers, which also present impediments to increasing autopsy rates. Our challenge as academic pathologists, whose careers have been molded by involvement in the autopsy, is to counter these trends. The challenges are great but the benefits for medicine and society are enormous.

Age-Specific Excess Mortality Patterns During the 1918-1920 Influenza Pandemic in Madrid, Spain

Although much progress has been made to uncover age-specific mortality patterns of the 1918 influenza pandemic in populations around the world, more studies in different populations are needed to make sense of the heterogeneous death impact of this pandemic. We assessed the absolute and relative magnitudes of 3 pandemic waves in the city of Madrid, Spain, between 1918 and 1920, on the basis of age-specific all-cause and respiratory excess death rates. Excess death rates were estimated using a Serfling model with a parametric bootstrapping approach to calibrate baseline death levels with quantified uncertainty. Excess all-cause and pneumonia and influenza mortality rates were estimated for different pandemic waves and age groups. The youngest and oldest persons experienced the highest excess mortality rates, and young adults faced the highest standardized mortality risk. Waves differed in strength; the peak standardized mortality risk occurred during the herald wave in spring 1918, but the highest excess rates occurred during the fall and winter of 1918/1919. Little evidence was found to support a “W”-shaped, age-specific excess mortality curve. Acquired immunity may have tempered a protracted fall wave, but recrudescent waves following the initial 2 outbreaks heightened the total pandemic mortality impact.

Back to the Future: Lessons Learned From the 1918 Influenza Pandemic

2018 marks the 100-year anniversary of the 1918 influenza pandemic, which killed ~50 million people worldwide. The severity of this pandemic resulted from a complex interplay between viral, host, and societal factors. Here, we review the viral, genetic and immune factors that contributed to the severity of the 1918 pandemic and discuss the implications for modern pandemic preparedness. We address unresolved questions of why the 1918 influenza H1N1 virus was more virulent than other influenza pandemics and why some people survived the 1918 pandemic and others succumbed to the infection. While current studies suggest that viral factors such as haemagglutinin and polymerase gene segments most likely contributed to a potent, dysregulated pro-inflammatory cytokine storm in victims of the pandemic, a shift in case-fatality for the 1918 pandemic toward young adults was most likely associated with the host's immune status. Lack of pre-existing virus-specific and/or cross-reactive antibodies and cellular immunity in children and young adults likely contributed to the high attack rate and rapid spread of the 1918 H1N1 virus. In contrast, lower mortality rate in in the older (>30 years) adult population points toward the beneficial effects of pre-existing cross-reactive immunity. In addition to the role of humoral and cellular immunity, there is a growing body of evidence to suggest that individual genetic differences, especially involving single-nucleotide polymorphisms (SNPs), contribute to differences in the severity of influenza virus infections. Co-infections with bacterial pathogens, and possibly measles and malaria, co-morbidities, malnutrition or obesity are also known to affect the severity of influenza disease, and likely influenced 1918 H1N1 disease severity and outcomes. Additionally, we also discuss the new challenges, such as changing population demographics, antibiotic resistance and climate change, which we will face in the context of any future influenza virus pandemic. In the last decade there has been a dramatic increase in the number of severe influenza virus strains entering the human population from animal reservoirs (including highly pathogenic H7N9 and H5N1 viruses). An understanding of past influenza virus pandemics and the lessons that we have learnt from them has therefore never been more pertinent.