SARS-CoV-2 Omicron virus causes attenuated disease in mice and hamsters.

The recent emergence of B.1.1.529, the Omicron variant1,2, has raised concerns of escape from protection by vaccines and therapeutic antibodies. A key test for potential countermeasures against B.1.1.529 is their activity in preclinical rodent models of respiratory tract disease. Here, using the collaborative network of the SARS-CoV-2 Assessment of Viral Evolution (SAVE) programme of the National Institute of Allergy and Infectious Diseases (NIAID), we evaluated the ability of several B.1.1.529 isolates to cause infection and disease in immunocompetent and human ACE2 (hACE2)-expressing mice and hamsters. Despite modelling data indicating that B.1.1.529 spike can bind more avidly to mouse ACE2 (refs. 3,4), we observed less infection by B.1.1.529 in 129, C57BL/6, BALB/c and K18-hACE2 transgenic mice than by previous SARS-CoV-2 variants, with limited weight loss and lower viral burden in the upper and lower respiratory tracts. In wild-type and hACE2 transgenic hamsters, lung infection, clinical disease and pathology with B.1.1.529 were also milder than with historical isolates or other SARS-CoV-2 variants of concern. Overall, experiments from the SAVE/NIAID network with several B.1.1.529 isolates demonstrate attenuated lung disease in rodents, which parallels preliminary human clinical data.

Swine H1N1 Influenza Virus Variants with Enhanced Polymerase Activity and HA Stability Promote Airborne Transmission in Ferrets.

Understanding how animal influenza A viruses (IAVs) acquire airborne transmissibility in humans and ferrets is needed to prepare for and respond to pandemics. Here, we investigated in ferrets the replication and transmission of swine H1N1 isolates P4 and G15, whose majority population had decreased polymerase activity and poor hemagglutinin (HA) stability, respectively. For both isolates, a minor variant was selected and transmitted in ferrets. Polymerase-enhancing variant PA-S321 airborne-transmitted and propagated in one ferret. HA-stabilizing variant HA1-S210 was selected in all G15-inoculated ferrets and was transmitted by contact and airborne routes. With an efficient polymerase and a stable HA, the purified minor variant G15-HA1-S210 had earlier and higher peak titers in inoculated ferrets and was recovered at a higher frequency after airborne transmission than P4 and G15. Overall, HA stabilization played a more prominent role than polymerase enhancement in the replication and transmission of these viruses in ferrets. The results suggest pandemic risk-assessment studies may benefit from deep sequencing to identify minor variants with human-adapted traits. IMPORTANCE Diverse IAVs circulate in animals, yet few acquire the viral traits needed to start a human pandemic. A stabilized HA and mammalian-adapted polymerase have been shown to promote the adaptation of IAVs to humans and ferrets (the gold-standard model for IAV replication, pathogenicity, and transmissibility). Here, we used swine IAV isolates of the gamma lineage as a model to investigate the importance of HA stability and polymerase activity in promoting replication and transmission in ferrets. These are emerging viruses that bind to both α-2,6- and α-2,3-linked receptors. Using isolates containing mixed populations, a stabilized HA was selected within days in inoculated ferrets. An enhanced polymerase was also selected and propagated after airborne transmission to a ferret. Thus, HA stabilization was a stricter requirement, yet both traits promoted transmissibility. Knowing the viral traits needed for pandemic potential, and the relative importance of each, will help identify emerging viruses of greatest concern.

Highly Pathogenic Avian Influenza A(H5N6) Virus Clade 2.3.4.4h in Wild Birds and Live Poultry Markets, Bangladesh.

Migratory birds play a major role in spreading influenza viruses over long distances. We report highly pathogenic avian influenza A(H5N6) viruses in migratory and resident ducks in Bangladesh. The viruses were genetically similar to viruses detected in wild birds in China and Mongolia, suggesting migration-associated dissemination of these zoonotic pathogens.

Continued Evolution of H5Nx Avian Influenza Viruses in Bangladeshi Live Poultry Markets: Pathogenic Potential in Poultry and Mammalian Models.

The genesis of novel influenza viruses through reassortment poses a continuing risk to public health. This is of particular concern in Bangladesh, where highly pathogenic avian influenza viruses of the A(H5N1) subtype are endemic and cocirculate with other influenza viruses. Active surveillance of avian influenza viruses in Bangladeshi live poultry markets detected three A(H5) genotypes, designated H5N1-R1, H5N1-R2, and H5N2-R3, that arose from reassortment of A(H5N1) clade 2.3.2.1a viruses. The H5N1-R1 and H5N1-R2 viruses contained HA, NA, and M genes from the A(H5N1) clade 2.3.2.1a viruses and PB2, PB1, PA, NP, and NS genes from other Eurasian influenza viruses. H5N2-R3 viruses contained the HA gene from circulating A(H5N1) clade 2.3.2.1a viruses, NA and M genes from concurrently circulating A(H9N2) influenza viruses, and PB2, PB1, PA, NP, and NS genes from other Eurasian influenza viruses. Representative viruses of all three genotypes and a parental clade 2.3.2.1a strain (H5N1-R0) infected and replicated in mice without prior adaptation; the H5N2-R3 virus replicated to the highest titers in the lung. All viruses efficiently infected and killed chickens. All viruses replicated in inoculated ferrets, but no airborne transmission was detected, and only H5N2-R3 showed limited direct-contact transmission. Our findings demonstrate that although the A(H5N1) viruses circulating in Bangladesh have the capacity to infect and replicate in mammals, they show very limited capacity for transmission. However, reassortment does generate viruses of distinct phenotypes.IMPORTANCE Highly pathogenic avian influenza A(H5N1) viruses have circulated continuously in Bangladesh since 2007, and active surveillance has detected viral evolution driven by mutation and reassortment. Recently, three genetically distinct A(H5N1) reassortant viruses were detected in live poultry markets in Bangladesh. Currently, we cannot assign pandemic risk by only sequencing viruses; it must be conducted empirically. We found that the H5Nx highly pathogenic avian influenza viruses exhibited high virulence in mice and chickens, and one virus had limited capacity to transmit between ferrets, a property considered consistent with a higher zoonotic risk.

Potential for Low-Pathogenic Avian H7 Influenza A Viruses To Replicate and Cause Disease in a Mammalian Model.

H7 subtype influenza A viruses are widely distributed and have been responsible for human infections and numerous outbreaks in poultry with significant impact. Despite this, the disease-causing potential of the precursor low-pathogenic (LP) H7 viruses from the wild bird reservoir has not been investigated. Our objective was to assess the disease-causing potential of 30 LP H7 viruses isolated from wild avian species in the United States and Canada using the DBA/2J mouse model. Without prior mammalian adaptation, the majority of viruses, 27 (90%), caused mortality in mice. Of these, 17 (56.7%) caused 100% mortality and 24 were of pathogenicity similar to that of A/Anhui/1/2013 (H7N9), which is highly pathogenic in mice. Viruses of duck origin were more pathogenic than those of shorebird origin, as 13 of 18 (72.2%) duck origin viruses caused 100% mortality while 4 of 12 (33.3%) shorebird origin viruses caused 100% mortality, despite there being no difference in mean lung viral titers between the groups. Replication beyond the respiratory tract was also evident, particularly in the heart and brain. Of the 16 viruses studied for fecal shedding, 11 were detected in fecal samples. These viruses exhibited a strong preference for avian-type α2,3-linked sialic acids; however, binding to mammalian-type α2,6-linked sialic acids was also detected. These findings indicate that LP avian H7 influenza A viruses are able to infect and cause disease in mammals without prior adaptation and therefore pose a potential public health risk. IMPORTANCE: Low-pathogenic (LP) avian H7 influenza A viruses are widely distributed in the avian reservoir and are the precursors of numerous outbreaks of highly pathogenic avian influenza viruses in commercial poultry farms. However, unlike highly pathogenic H7 viruses, the disease-causing potential of LP H7 viruses from the wild bird reservoir has not been investigated. To address this, we studied 30 LP avian H7 viruses isolated from wild avian species in the United States and Canada using the DBA/2J mouse model. Surprisingly, the majority of these viruses, 90%, caused mortality in mice without prior mammalian adaptation, and 56.7% caused 100% mortality. There was also evidence of spread beyond the respiratory tract and fecal shedding. Therefore, the disease-causing potential of LP avian H7 influenza A viruses in mammals may be underestimated, and these viruses therefore pose a potential public health risk.

Genesis of Influenza A(H5N8) Viruses.

Highly pathogenic avian influenza A(H5N8) clade 2.3.4.4 virus emerged in 2016 and spread to Russia, Europe, and Africa. Our analysis of viruses from domestic ducks at Tanguar haor, Bangladesh, showed genetic similarities with other viruses from wild birds in central Asia, suggesting their potential role in the genesis of A(H5N8).

Stat1-Deficient Mice Are Not an Appropriate Model for Efficacy Testing of Recombinant Vesicular Stomatitis Virus-Based Filovirus Vaccines.

Stat1(-/-) mice lack a response to interferon α, ß, and γ, allowing for replication of nonadapted wild-type (wt) Ebolavirus and Marburgvirus. We sought to establish a mouse model for efficacy testing of live attenuated recombinant vesicular stomatitis virus (rVSV)-based filovirus vaccine vectors using wt Ebolavirus and Marburgvirus challenge strains. While infection of immunocompetent mice with different rVSV-based filovirus vectors did not cause disease, infection of Stat1(-/-) mice with the same vectors resulted in systemic infection and lethal outcome for the majority of tested rVSVs. Despite differences in viral loads, organ tropism was remarkably similar between rVSV filovirus vaccine vectors and rVSVwt, with the exception of the brain. In conclusion, Stat1(-/-) mice are not an appropriate immunocompromised mouse model for efficacy testing of live attenuated, replication-competent rVSV vaccine vectors.

Impact of Adjuvants on the Immunogenicity and Efficacy of Split-Virion H7N9 Vaccine in Ferrets.

BACKGROUND: An effective vaccine is urgently needed against the H7N9 avian influenza virus. We evaluated the immunogenicity and protective efficacy of a split-virion H7N9 vaccine with or without the oil-in-water adjuvants in ferrets. METHODS: Ferrets were vaccinated with 2 doses of unadjuvanted, MF59 or AS03-adjuvanted A/Shanghai/2/2013 (H7N9) vaccine, and the induction of antibodies to hemagglutinin (HA) or neuraminidase proteins was evaluated. Ferrets were then challenged with wild-type H7N9 virus to assess the vaccine's protective efficacy. The vaccine composition and integrity was also evaluated in vitro. RESULTS: Adjuvanted vaccines stimulated robust serum antibody titers against HA and neuraminidase compared with the unadjuvanted vaccines. Although there was a difference in adjuvanticity between AS03 and MF59 at a lower dose (3.75 µg of HA), both adjuvants induced comparable antibody responses after 2 doses of 15 µg. On challenge, ferrets that received adjuvanted vaccines showed lower viral burden than the control or unadjuvanted vaccine group. In vitro examinations revealed that the vaccine contained visible split-virus particles and retained the native conformation of HA recognizable by polyclonal and monoclonal antibodies. CONCLUSIONS: The adjuvanted H7N9 vaccines demonstrated superior immunogenicity and protective efficacy against H7N9 infection in ferrets and hold potential as a vaccination regimen.

Human H7N9 and H5N1 influenza viruses differ in induction of cytokines and tissue tropism.

UNLABELLED: Since emerging in 2013, the avian-origin H7N9 influenza viruses have resulted in over 400 human infections, leading to 115 deaths to date. Although the epidemiology differs from human highly pathogenic avian H5N1 influenza virus infections, there is a similar rapid progression to acute respiratory distress syndrome. The aim of these studies was to compare the pathological and immunological characteristics of a panel of human H7N9 and H5N1 viruses in vitro and in vivo. Although there were similarities between particular H5N1 and H7N9 viruses, including association between lethal disease and spread to the alveolar spaces and kidney, there were also strain-specific differences. Both H5N1 and H7N9 viruses are capable of causing lethal infections, with mortality correlating most strongly with wider distribution of viral antigen in the lungs, rather than with traditional measures of virus titer and host responses. Strain-specific differences included hypercytokinemia in H5N1 infections that was not seen with the H7N9 infections regardless of lethality. Conversely, H7N9 viruses showed a greater tropism for respiratory epithelium covering nasal passages and nasopharynx-associated lymphoid tissue than H5N1 viruses, which may explain the enhanced transmission in ferret models. Overall, these studies highlight some distinctive properties of H5N1 and H7N9 viruses in different in vitro and in vivo models. IMPORTANCE: The novel avian-origin H7N9 pandemic represents a serious threat to public health. The ability of H7N9 to cause serious lung pathology, leading in some cases to the development of acute respiratory distress syndrome, is of particular concern. Initial reports of H7N9 infection compared them to infections caused by highly pathogenic avian (HPAI) H5N1 viruses. Thus, it is of critical importance to understand the pathology and immunological response to infection with H7N9 compared to HPAI H5N1 viruses. We compared these responses in both in vitro and in vivo models, and found that H5N1 and H7N9 infections exhibit distinct pathological, immunological, and tissue tropism differences that could explain differences in clinical disease and viral transmission.

Development of a nucleoside-modified mRNA vaccine against clade 2.3.4.4b H5 highly pathogenic avian influenza virus.

mRNA lipid nanoparticle (LNP) vaccines would be useful during an influenza virus pandemic since they can be produced rapidly and do not require the generation of egg-adapted vaccine seed stocks. Highly pathogenic avian influenza viruses from H5 clade 2.3.4.4b are circulating at unprecedently high levels in wild and domestic birds and have the potential to adapt to humans. Here, we generate an mRNA lipid nanoparticle (LNP) vaccine encoding the hemagglutinin (HA) glycoprotein from a clade 2.3.4.4b H5 isolate. The H5 mRNA-LNP vaccine elicits strong T cell and antibody responses in female mice, including neutralizing antibodies and broadly-reactive anti-HA stalk antibodies. The H5 mRNA-LNP vaccine elicits antibodies at similar levels compared to whole inactivated vaccines in female mice with and without prior H1N1 exposures. Finally, we find that the H5 mRNA-LNP vaccine is immunogenic in male ferrets and prevents morbidity and mortality of animals following 2.3.4.4b H5N1 challenge. Together, our data demonstrate that a monovalent mRNA-LNP vaccine expressing 2.3.4.4b H5 is immunogenic and protective in pre-clinical animal models.

Highly pathogenic avian influenza A(H5N1) virus in a common bottlenose dolphin (Tursiops truncatus) in Florida.

Since late 2021, highly pathogenic avian influenza (HPAI) viruses of A/goose/Guangdong/1/1996 (H5N1) lineage have caused widespread mortality in wild birds and poultry in the United States. Concomitant with the spread of HPAI viruses in birds are increasing numbers of mammalian infections, including wild and captive mesocarnivores and carnivores with central nervous system involvement. Here we report HPAI, A(H5N1) of clade 2.3.4.4b, in a common bottlenose dolphin (Tursiops truncatus) from Florida, United States. Pathological findings include neuronal necrosis and inflammation of the brain and meninges, and quantitative real time RT-PCR reveal the brain carried the highest viral load. Virus isolated from the brain contains a S246N neuraminidase substitution which leads to reduced inhibition by neuraminidase inhibitor oseltamivir. The increased prevalence of A(H5N1) viruses in atypical avian hosts and its cross-species transmission into mammalian species highlights the public health importance of continued disease surveillance and biosecurity protocols.

Cross-species spill-over potential of the H9N2 bat influenza A virus.

In 2017, a novel influenza A virus (IAV) was isolated from an Egyptian fruit bat. In contrast to other bat influenza viruses, the virus was related to avian A(H9N2) viruses and was probably the result of a bird-to-bat transmission event. To determine the cross-species spill-over potential, we biologically characterize features of A/bat/Egypt/381OP/2017(H9N2). The virus has a pH inactivation profile and neuraminidase activity similar to those of human-adapted IAVs. Despite the virus having an avian virus-like preference for α2,3 sialic acid receptors, it is unable to replicate in male mallard ducks; however, it readily infects ex-vivo human respiratory cell cultures and replicates in the lungs of female mice. A/bat/Egypt/381OP/2017 replicates in the upper respiratory tract of experimentally-infected male ferrets featuring direct-contact and airborne transmission. These data suggest that the bat A(H9N2) virus has features associated with increased risk to humans without a shift to a preference for α2,6 sialic acid receptors.

Hemagglutinin destabilization in H3N2 vaccine reference viruses skews antigenicity and prevents airborne transmission in ferrets.

During influenza virus entry, the hemagglutinin (HA) protein binds receptors and causes membrane fusion after endosomal acid activation. To improve vaccine efficiency and pandemic risk assessment for currently-dominant H3N2 influenza viruses, we investigated HA stability of 6 vaccine reference viruses and 42 circulating viruses. Recent vaccine reference viruses had destabilized HA proteins due to egg-adaptive mutation HA1-L194P. Virus growth in cell culture was independent of HA stability. In ferrets, the vaccine reference viruses and circulating viruses required a relatively stable HA (activation and inactivation pH < 5.5) for airborne transmissibility. The recent vaccine reference viruses with destabilized HA proteins had reduced infectivity, had no airborne transmissibility unless reversion to HA1-P194L occurred, and had skewed antigenicity away from the studied viruses and circulating H3N2 viruses. Other vaccine reference viruses with stabilized HAs retained infectivity, transmissibility, and antigenicity. Therefore, HA stabilization should be prioritized over destabilization in vaccine reference virus selection to reduce mismatches between vaccine and circulating viruses.

Emergence of a new genotype of clade 2.3.4.4b H5N1 highly pathogenic avian influenza A viruses in Bangladesh.

Influenza virological surveillance was conducted in Bangladesh from January to December 2021 in live poultry markets (LPMs) and in Tanguar Haor, a wetland region where domestic ducks have frequent contact with migratory birds. The predominant viruses circulating in LPMs were low pathogenic avian influenza (LPAI) H9N2 and clade 2.3.2.1a highly pathogenic avian influenza (HPAI) H5N1 viruses. Additional LPAIs were found in both LPM (H4N6) and Tanguar Haor wetlands (H7N7). Genetic analyses of these LPAIs strongly suggested long-distance movement of viruses along the Central Asian migratory bird flyway. We also detected a novel clade 2.3.4.4b H5N1 virus from ducks in free-range farms in Tanguar Haor that was similar to viruses first detected in October 2020 in The Netherlands but with a different PB2. Identification of clade 2.3.4.4b HPAI H5N1 viruses in Tanguar Haor provides continued support of the role of migratory birds in transboundary movement of influenza A viruses (IAV), including HPAI viruses. Domestic ducks in free range farm in wetland areas, like Tangua Haor, serve as a conduit for the introduction of LPAI and HPAI viruses into Bangladesh. Clade 2.3.4.4b viruses have dominated in many regions of the world since mid-2021, and it remains to be seen if these viruses will replace the endemic clade 2.3.2.1a H5N1 viruses in Bangladesh.

Development of a nucleoside-modified mRNA vaccine against clade 2.3.4.4b H5 highly pathogenic avian influenza virus.

Highly pathogenic avian influenza viruses from H5 clade 2.3.4.4b are circulating at unprecedently high levels in wild and domestic birds and have the potential to adapt to humans. We generated an mRNA lipid nanoparticle (LNP) vaccine encoding the hemagglutinin (HA) glycoprotein from a clade 2.3.4.4b H5 isolate. We show that the vaccine is immunogenic in mice and ferrets and prevents morbidity and mortality of ferrets following 2.3.4.4b H5N1 challenge.

Rapid evolution of A(H5N1) influenza viruses after intercontinental spread to North America.

Highly pathogenic avian influenza A(H5N1) viruses of clade 2.3.4.4b underwent an explosive geographic expansion in 2021 among wild birds and domestic poultry across Asia, Europe, and Africa. By the end of 2021, 2.3.4.4b viruses were detected in North America, signifying further intercontinental spread. Here we show that the western movement of clade 2.3.4.4b was quickly followed by reassortment with viruses circulating in wild birds in North America, resulting in the acquisition of different combinations of ribonucleoprotein genes. These reassortant A(H5N1) viruses are genotypically and phenotypically diverse, with many causing severe disease with dramatic neurologic involvement in mammals. The proclivity of the current A(H5N1) 2.3.4.4b virus lineage to reassort and target the central nervous system warrants concerted planning to combat the spread and evolution of the virus within the continent and to mitigate the impact of a potential influenza pandemic that could originate from similar A(H5N1) reassortants.

Pandemic swine-origin H1N1 influenza A virus isolates show heterogeneous virulence in macaques.

The first influenza pandemic of the new millennium was caused by a newly emerged swine-origin influenza virus (SOIV) (H1N1). This new virus is characterized by a previously unknown constellation of gene segments derived from North American and Eurasian swine lineages and the absence of common markers predictive of human adaptation. Overall, human infections appeared to be mild, but an alarming number of young individuals presented with symptoms atypical for seasonal influenza. The new SOIV also showed a sustained human-to-human transmissibility and higher reproduction ratio than common seasonal viruses, altogether indicating a higher pathogenic potential for this newly emerged virus. To study the virulence of the SOIV, we used a recently established cynomolgus macaque model and compared parameters of clinical disease, virology, host responses, and pathology/histopathology with a current seasonal H1N1 virus. We here show that infection of macaques with two genetically similar but clinically distinct SOIV isolates from the early stage of the pandemic (A/Mexico/4108/2009 and A/Mexico/InDRE4487/2009) resulted in upper and lower respiratory tract infections and clinical disease ranging from mild to severe pneumonia that was clearly advanced over the mild infection caused by A/Kawasaki/UTK-4/2009, a current seasonal strain. Unexpectedly, we observed heterogeneity among the two SOIV isolates in virus replication, host transcriptional and cytokine responses, and disease progression, demonstrating a higher pathogenic potential for A/Mexico/InDRE4487/2009. Differences in virulence may explain more severe disease, as was seen with certain individuals infected with the emerged pandemic influenza virus. Thus, the nonhuman primate model closely mimics influenza in humans.

It's the Wrong Virus: Rapid Adaptation of Operations Inside a Highly Pathogenic Avian Influenza Select Agent Laboratory in Response to the 2019 SARS-CoV-2 Pandemic.

Background: The Animal Biosafety Level 3 Enhanced (ABSL-3+) laboratory at St. Jude Children's Research Hospital has a long history of influenza pandemic preparedness. The emergence of SARS-CoV-2 and subsequent expansion into a pandemic has put new and unanticipated demands on laboratory operations since April 2020. Administrative changes, investigative methods requiring increased demand for inactivation and validation of sample removal, and the adoption of a new animal model into the space required all arms of our Biorisk Management System (BMS) to respond with speed and innovation. Results: In this report, we describe the outcomes of three major operational changes that were implemented to adapt the ABSL-3+ select agent space into a multipathogen laboratory. First were administrative controls that were revised and developed with new Institutional Biosafety Committee protocols, laboratory space segregation, training of staff, and occupational health changes for potential exposure to SARS-CoV-2 inside the laboratory. Second were extensive inactivation and validation experiments performed for both highly pathogenic avian influenza and SARS-CoV-2 to meet the demands for sample removal to a lower biosafety level. Third was the establishment of a new caging system to house Syrian Golden hamsters for SARS-CoV-2 risk assessment modeling. Summary: The demands placed on biocontainment laboratories for response to SARS-CoV-2 has highlighted the importance of a robust BMS. In a relatively short time, the ABSL-3+ was able to adapt from a single select agent space to a multipathogen laboratory and expand our pandemic response capacity.

Distinct but connected avian influenza virus activities in wetlands and live poultry markets in Bangladesh, 2018-2019.

From April 2018 to October 2019, we continued active surveillance for influenza viruses in Bangladeshi live poultry markets (LPMs) and in Tanguar Haor, a wetland region of Bangladesh where domestic ducks have frequent contact with migratory birds. The predominant virus subtypes circulating in the LPMs were low pathogenic avian influenza (LPAI) H9N2 and clade 2.3.2.1a highly pathogenic avian influenza (HPAI) H5N1 viruses of the H5N1-R1 genotype, like those found in previous years. Viruses of the H5N1-R2 genotype, which were previously reported as co-circulating with H5N1-R1 genotype viruses in LPM, were not detected. In addition to H9N2 viruses, which were primarily found in chicken and quail, H2N2, H3N8 and H11N3 LPAI viruses were detected in LPMs, exclusively in ducks. Viruses in domestic ducks and/or wild birds in Tanguar Haor were more diverse, with H1N1, H4N6, H7N1, H7N3, H7N4, H7N6, H8N4, H10N3, H10N4 and H11N3 detected. Phylogenetic analyses of these LPAI viruses suggested that some were new to Bangladesh (H2N2, H7N6, H8N4, H10N3 and H10N4), likely introduced by migratory birds of the Central Asian flyway. Our results show a complex dynamic of viral evolution and diversity in Bangladesh based on factors such as host populations and geography. The LPM environment was characterised by maintenance of viruses with demonstrated zoonotic potential and H5N1 genotype turnover. The wetland environment was characterised by greater viral gene pool diversity but a lower overall influenza virus detection rate. The genetic similarity of H11N3 viruses in both environments demonstrates that LPM and wetlands are connected despite their having distinct influenza ecologies.

A novel model of lethal Hendra virus infection in African green monkeys and the effectiveness of ribavirin treatment.

The henipaviruses, Hendra virus (HeV) and Nipah virus (NiV), are emerging zoonotic paramyxoviruses that can cause severe and often lethal neurologic and/or respiratory disease in a wide variety of mammalian hosts, including humans. There are presently no licensed vaccines or treatment options approved for human or veterinarian use. Guinea pigs, hamsters, cats, and ferrets, have been evaluated as animal models of human HeV infection, but studies in nonhuman primates (NHP) have not been reported, and the development and approval of any vaccine or antiviral for human use will likely require efficacy studies in an NHP model. Here, we examined the pathogenesis of HeV in the African green monkey (AGM) following intratracheal inoculation. Exposure of AGMs to HeV produced a uniformly lethal infection, and the observed clinical signs and pathology were highly consistent with HeV-mediated disease seen in humans. Ribavirin has been used to treat patients infected with either HeV or NiV; however, its utility in improving outcome remains, at best, uncertain. We examined the antiviral effect of ribavirin in a cohort of nine AGMs before or after exposure to HeV. Ribavirin treatment delayed disease onset by 1 to 2 days, with no significant benefit for disease progression and outcome. Together our findings introduce a new disease model of acute HeV infection suitable for testing antiviral strategies and also demonstrate that, while ribavirin may have some antiviral activity against the henipaviruses, its use as an effective standalone therapy for HeV infection is questionable.