Influenza
Implicating results of H5N1 avian influenza virus laboratory study in ducks
By Nilesh, WHO Correspondent
Nov 4, 2004, 08:35

- Highly pathogenic H5N1 virus replicates in the respiratory and intestinal tracts of experimentally infected domestic ducks and contact ducks. Large amounts of virus (103.5 � 10 5.5 per ml) are excreted via the respiratory route as well as in faeces.

- No symptoms or deaths were observed in the majority of ducks and contacts infected with human and chicken H5N1 viruses from the 2004 outbreaks in Viet Nam.

- The amounts of H5N1 virus shed are sufficient to allow transmission of H5N1 infection directly from apparently healthy ducks to chickens.

- All infected ducks shed virus for 11 days and some for 17 days and longer. In comparison, ducks infected with an H5N1 virus isolated in 2003 shed virus for a maximum of 10 days.

- Preliminary results on the environmental stability indicate that H5N1 viruses from the 2004 outbreaks have become more stable. H5N1 viruses from 2004 survived at 37oC for 6 days, compared with 2 days for viruses from the 1997 outbreak.

The studies were completed last week by researchers at the WHO collaborating centre for animal influenza viruses at St Jude Children�s Research Hospital in Memphis, USA. The main findings are being made public, in advance of publication, because of their significance for human health.


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