Thursday, April 5, 2007

H5N1 and Drinking Water

Just received and interesting Q&A update from WHO WatSan team on what the risks may be for transmitting H5N1 through drinking water. This question became especially relevant for CARE during the recent floods in Jakarta, where H5N1 in poultry is widespread.

Here's a few of the truncated Q&A's below, if you'd like the whole document, email us at: There's also a good background paper on the latest evidence at:

From WHO:

Q. Is there a risk from drinking water?
A. Potentially Yes.

Avian influenza viruses can persist for extended periods of time in water depending on temperature, pH and salinity but information on environmental persistence of H5N1 in water is lacking. As influenza A (H5N1) infection is frequently accompanied by gastrointestinal symptoms this could mean that H5N1 might enter the host also through Gastrointestinal tract.
Based on no evidence but considering a potential risk. Knowing that water supplied for multiple use and for drinking water in health-care facilities, minimum standards are required based on national protocols.

Q. How does avian influenza virus get into drinking water sources?

A. Infected waterfowl carry avian influenza viruses in their gastrointestinal tract, where the virus replicates. Birds infected with avian influenza virus shed large quantities of virus in their faeces as well as in their saliva and nasal secretions. Recent studies of ducks inoculated with H5N1 isolates from 2003 and 2004 showed infective virus shedding up to 17 days post-infection. Thus, it is likely that infected droppings or other secretions from both symptomatic and asymptomatic waterfowl will enter water environments where these birds gather. Avian influenza virus has been isolated from unconcentrated lake water where ducks gathered and deposited large amounts of faeces, but virus concentrations were not determined in these studies. Still, avian influenza virus detection in unconcentrated water and in small sample volumes suggests that levels could be relatively high.

While there have been no quantitative studies on the transport of avian influenza virus to groundwater underlying poultry operations, the disposal and composting of infected waste on poultry farms could create a potential pathway for the virus to enter groundwater. Similarly, interconnected surface water and groundwater systems might provide a potential route to groundwater if surface waters are carrying high concentrations of the virus.

Q. Do we know how long avian influenza viruses persist in drinking water sources?

A. Avian influenza viruses are known to persist for extended periods of time in water depending on environmental conditions, including temperature, pH and salinity, but information on the persistence of highly pathogenic avian influenza (HPAI) viruses, including H5N1, in water is lacking. Persistence of avian influenza in water is most sensitive to temperature.

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