FLU NEWS SCAN: H5N1 in Cambodia, mutant H5N1 study in ferrets, flu in seals

Nov 7, 2011

H5N1 hits Cambodian poultry farm
Cambodia's agriculture ministry today reported that the H5N1 avian influenza virus struck a broiler farm in Battambang province, located in the northwestern part of the country, according a report to the World Organization for Animal Health (OIE). The event began on Nov 3, killing 1,050 of 5,206 susceptible birds. Provincial and central authorities culled the remaining 4,156 poultry to control the spread of the virus. The National Veterinary Research Institute conducted an investigation but did not determine the source of the outbreak. Cambodia reported its last H5N1 outbreak in September.
Nov 7 OIE report

Study finds series of complex steps needed for airborne H5N1 spread in ferrets
A series of complex changes allowed the H5N1 avian flu virus to become transmissible via airborne droplets in ferrets, US researchers reported in Virology. Working on the assumption that acquisition of alpha-2-6 sialoside receptor specificity by alpha-2-3–specific H5N1 is a prerequisite for efficient transmission in humans, they identified four variant viruses that had modestly increased alpha-2-6 and minimally decreased alpha-2-3 binding. They then created a mutant virus combining one of these variants (Q196R) with mutations from previous pandemic viruses (Q226L and G228S) that had predominantly alpha-2-6 binding. This novel virus was transmitted between ferrets, which are seen as good models of flu transmission in humans. Spread, however, occurred by direct contact, not by airborne droplets. The team then created a reassortant virus containing the mutant hemagglutinin, a human N2 neuraminidase, and internal genes from an H5N1 virus, and observed that it was "partially transmitted via respiratory droplets." The researchers conclude, "The complex changes required for airborne transmissibility in ferrets suggest that extensive evolution is needed for H5N1 transmissibility in humans."
Nov 5 Virology abstract

Influenza A investigated in New England seal deaths
Animal health officials in New England are exploring the role influenza A may have played in a large number of seal deaths reported along the region's coast since September, the National Oceanic Atmospheric Administration (NOAA) said in a Nov 4 statement. Preliminary pathology, toxin, and virology tests on five seals found that that all tested positive for influenza A. NOAA cautioned that the results only apply to those five seals, and more tests are under way to determine what led to the deaths of 146 seals. The die-off has been declared an "unusual mortality event," which allows NOAA to devote more resources to determining the cause of death. Dr Teri Rowles, from NOAA's fisheries services, in the statement warned people to avoid exposing themselves and their pets to the seals as authorities gauge if there are any potential risks to human health.
Nov 4 NOAA press release

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