transmission electron micrograph (tem) of negatively stained influenza virus particles (small , white) attached host cells (large , irregular) (late passage). (source: dr. erskine palmer, centers disease control , prevention public health image library)
infected birds transmit h5n1 through saliva, nasal secretions, feces , blood. other animals may become infected virus through direct contact these bodily fluids or through contact surfaces contaminated them. h5n1 remains infectious after on 30 days @ 0 °c ( 32.0 °f) (over 1 month @ freezing temperature) or 6 days @ 37 °c ( 98.6 °f) (one week @ human body temperature); @ ordinary temperatures lasts in environment weeks. in arctic temperatures, not degrade @ all.
because migratory birds among carriers of highly pathogenic h5n1 virus, spreading parts of world. h5n1 different known highly pathogenic avian flu viruses in ability spread animals other poultry.
in october 2004, researchers discovered h5n1 far more dangerous believed. waterfowl revealed directly spreading highly pathogenic strain chickens, crows, pigeons, , other birds, , virus increasing ability infect mammals, well. point on, avian flu experts increasingly referred containment strategy can delay, not prevent, future avian flu pandemic.
since 1997, studies of influenza (h5n1) indicate these viruses continue evolve, changes in antigenicity , internal gene constellations; expanded host range in avian species , ability infect felids; enhanced pathogenicity in experimentally infected mice , ferrets, in cause systemic infections; , increased environmental stability.
the new york times, in article on transmission of h5n1 through smuggled birds, reports wade hagemeijer of wetlands international stating, believe spread both bird migration , trade, trade, particularly illegal trade, more important .
on september 27, 2007 researchers reported h5n1 bird flu virus can pass through pregnant woman s placenta infect fetus. found evidence of doctors had long suspected — virus not affects lungs, passes throughout body gastrointestinal tract, brain, liver, , blood cells.
in may 2013, north korea confirmed h5n1 bird flu outbreak forced authorities kill on 160,000 ducks in pyongyang.
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