ETIDIOH - NEW

  Abstract Currently, there is limited knowledge on the impact of immunity to hemagglutinin (HA) and/or neuraminidase (NA) on the transmission of influenza viruses . Therefore, using intramuscular vaccination , intranasal vaccination , or infection with reassortant viruses , we induced immunity to each antigen alone or both antigens combined in ferrets . We then assessed transmission of the 2009 pandemic H1N1 virus from these ferrets to naïve respiratory contacts . For all strategies used to induce immunity, combined immunity to HA and NA resulted in the largest reductions in transmission . Moreover, immunity to HA and NA conferred additive rather than synergistic reductions in transmission. No escape variants emerged in our transmission studies, and logistical regression showed that the probability of transmission was less than 50% when viral titers in donors were reduced to 101.5 and 102 median tissue culture infectious dose per ml on days 1 and 3 postinfection, respectively. The...

  Abstract The ongoing outbreak of highly pathogenic avian influenza virus (HPAIV) subtype H5N1 in the U.S. poses a significant public health threat . To date, 70 human cases have been confirmed in the United States , including two severe cases and one fatality . While suitable animal models are crucial for predicting the potential pandemic risk of newly emerging pathogens in humans, studies investigating contemporary HPAIV H5N1 transmission dynamics remain limited. Here, we investigate the pathogenicity and transmission efficiency of recent clade 2.3.4.4b H5N1 viruses isolated from a bovine, mountain lion, and a human case using Syrian hamsters . Intranasal inoculation results in productive virus replication in the respiratory tract and shedding for all three isolates . Transmission studies demonstrate limited efficiency via direct contact and airborne routes for all isolates. Although overall transmission is inefficient , the human H5N1 isolate demonstrates relatively greater con...

  ABSTRACT Ferrets are widely used to model airborne transmission of influenza viruses in humans . Airborne transmission is evaluated by infecting donor ferrets with a high virus dose and monitoring transmission to contact animals sharing the same airspace . Humans can be infected with a broad range of influenza virus doses . Therefore, we evaluated the relationship between inoculation dose and transmission for two pandemic influenza viruses in ferrets . Donor ferrets were inoculated with 100 to 106 tissue culture infectious dose 50 (TCID50) of the 2009 pandemic H1N1 or 1968 pandemic H3N2 virus and were then paired with respiratory contacts . Using the proportion of donors that became infected across virus doses, we calculated the infectious dose 50 (ID50). Subsequently, by comparing the proportion of contacts that became infected, we calculated the transmissible dose 50% (TD50): the donor inoculation dose that resulted in transmission to 50% of contacts . For the 2009 pandemic H1N...

  Abstract Recent A(H5N1) zoonotic cases linked to poultry and cattle in North America highlight the urgent need to assess the pandemic potential of emerging strains . Using male ferrets , we evaluate two B3.13 and two D1.1 genotype A(H5N1) viruses isolated from humans and observe fatal disease and varying capacities for direct contact transmission . To enhance pandemic risk assessment , we conduct aerosol sampling using cyclone BC251 and water condensation capture-based SPOT samplers and perform comparative analyses to include additional A(H5N1), A(H9N2), A(H7N9), and A(H1N1)pdm09 strains with known transmissibility profiles. Although none of the A(H5N1) strains transmit via the air, B3.13 viruses are detected at significantly higher levels compared to D1.1 strains . Here we show strong correlations between viral loads in nasal washes, airborne virus shedding, and transmissibility in ferrets , highlighting the value of these metrics for identifying zoonotic influenza viruses that ...