Avian influenza (H5N1) in China

There are recent reports of highly pathogenic avian influenza (H5N1) from Qinqhai Nature Preserve in Qinqhai Province, China (west of Xining; see here for a description of the area), a significant extension of the known affected area for this disease.

Previous to this report, the current H5N1 outbreak was thought to be
contained to Southeast Asia (see map).

There are many rumours circulating about this issue, and given the propensity of the media to speculation, it is important to keep in mind what we know and what we don't know.

Why is this important?
The current outbreak of H5N1 avian influenza in Southeast Asia has been making news headlines for over a year now. Millions of domestic poultry have been affected throughout southeast Asia and over 50 humans have died to date. In the last 100 years there have been three pandemics of avian influenza in humans, the most lethal of which occuring in 1918-1919. Well over 20 million people died in that outbreak. Many scientists and health practitioners are warning that it is only a matter of time before the next global influenza pandemic occurs. The current strain circulating in Southeast Asia does not transmit efficiently among humans. However, there is great worry that with continued exposure to humans, the virus may evolve greater transmissibility through mutation or by obtaining genetic material from human influenza viruses.

What we know:

- Disease reports: in its report to the Office International des Epizooties (an international body responsible for fighting infectious diseases), China reported that 519 individuals of 5 species (bar-headed goose (Anser indicus), great black-headed gull (Larus ichthyaetus), brown-headed gull (Larus brunnicephalus), ruddy shelduck (Tadorna ferruginea) and great cormorant (Phalacrocorax carbo)) were found dead at Qinghai Lake Nature Reserve. Although H5N1 avian influenza was initially ruled out as the cause of death, it has subsequently been identified at the site. All these birds are migratory.

- Control measures: There are reports that China has closed all nature preserves to visitors, including Qinqhai NP. Three million doses of vaccine have been shipped to the province, presumably to vaccinate poultry in the area. Further, special clinics have been set up to screen humans with fevers or pneumonia for influenza infection.

Critical information that we don't know:

- We don't actually know what killed these birds. Apparently as many as 100,000 birds congregate on this lake, and so 500 dead birds may not be unusual, and it is possible that avian influenza was isolated from birds that died of something else. Cause-of-death determinations may have been done, but those data are not publicly available presently. If they were not done, it may be too late to determine cause-of-death in this case, but such determinations are a
critical part of any disease outbreak.

- We don't know how many of these 519 birds actually had avian influenza. In some die-offs, detailed investigation is done on a few animals, and then the results of those investigations are extrapolated to the rest of the dead animals.

- We don't know if the virus isolated from these birds is related to
the virus circulating in Southeast Asia. The isolate should be sequenced and the sequence deposited at GENBANK so that comparisons can be made.

- We don't know how or where these birds got infected. H5N1 avian influenza is known to be circulating in domestic poultry in Southeast Asia, but very few wild birds have been found with the virus there. It is possible that one of these five bird species (or one of the many other species that congregate there) brought the virus to the preserve from Southeast Asia. Alternatively, it is also possible that there is an unreported outbreak of H5N1 in domestic poultry in central China from which the wild birds picked up the virus. Transparent reporting
from China on the disease status of their domestic poultry is necessary.

- In the region, there are unsubstantiated reports of human deaths due to an unknown cause. Some bloggers have speculated that these are human cases of influenza, but at this point there is no evidence for or against this theory. The Chinese government is saying there are no
human cases. Again, transparent reporting is necessary.

Why is this a conservation issue?
Avian influenza forms a threat to wild bird conservation on several fronts. First, although most strains of avian influenza relatively benign, H5N1 appears to be able to cause illness and death in wild birds. Second, there may be calls for culling of wild birds to try to control or limit the spread of H5N1, although it is recognized in the wildlife health community that culling of wild birds is not an effective control measure, and that there is no evidence that wild birds play a major role in influenza epidemiology.

The most effective way to prevent transmission of avian influenza between domestic poultry and wild birds is to improve biosecurity around poultry farms. The key goal of improved biosecurity would be to reduce or prevent contact between wild birds and domestic poultry
and their wastes.