Questions and Answers About Avian Flu

What causes avian influenza?

Avian influenza is caused by viruses that occur mostly in birds but that can be transmitted to humans. Most of these viruses cause only mild symptoms in birds and are found worldwide. The high pathogenicity H5N1 strains are of current concern because they have caused deadly outbreaks in poultry and, to a lesser extent, in waterfowl and shorebirds in Africa, Asia, Europe, and the Near East. Most outbreaks in humans have been tied to poultry or poultry products. There have been no documented cases of transmission from wild birds to humans.

What is the risk to humans?

As of April 2006, there have been no reports of highly pathogenic H5N1 avian influenza in humans or birds in North America. The risk of contracting the H5N1 virus is extremely low. Even in areas with outbreaks, where the risk is higher, the virus is not easily transmitted from birds to people. Most cases of human deaths have occurred after direct contact with infected poultry or contaminated surfaces and poultry products. In the few cases of possible human-to-human infection, the disease has not spread beyond a single person.

By April 11, 2006, the World Health Organization had confirmed 109 deaths from H5N1 in 9 countries since 2003. In comparison, the Centers for Disease Control estimates that other forms of flu cause about 36,000 deaths each year in the United States alone.

Health officials are concerned about avian flu because of the potential for the virus to mutate into a form that is more contagious among humans.

When and how is avian flu predicted to arrive in North America?

No one knows, but the United States government has surveillance programs to detect the virus as early as possible.

The commercial poultry industry is the major concern because the virus is most likely to mutate to more harmful forms among crowded poultry flocks in contact with humans. Exportation of poultry and hatching eggs can spread the disease to other countries. The United States has banned poultry from areas affected by avian flu.

The United States has also banned pet birds and bird products from countries affected by H5N1. All live birds imported from other countries are quarantined, but the illegal trade of caged birds is more difficult to monitor.

It is possible that wild birds from Asia or Europe could carry the virus to their breeding grounds in Alaska or Canada, then transmit the disease to species that migrate to the Lower 48. The United States government will be using harmless swab tests on 75,000--100,000 birds in 2006.

If the H5N1 virus is detected in North America, it will not signal the start of a pandemic because the virus is not easily transmissible to or between humans.

Are wild birds spreading the disease?

Wild birds can carry the virus with them when they migrate, but in most cases so far, they appear to have contracted the disease from poultry rather than vice-versa.

In most cases, new outbreaks of avian flu originated with the poultry industry. In outbreaks among wild birds in Azerbaijan, Croatia, Greece, and Turkey in autumn 2005, the birds may have contracted the virus from infected poultry flocks in the Black Sea region, then dispersed to warmer regions, carrying the virus with them.

About 5-10 percent of the world?s population of Bar-headed Geese was estimated to have died in an avian flu outbreak in Qinghai, China.

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In spring 2005, some 6,000 wild birds, mostly Bar-headed Geese, died in an outbreak at Qinghai Lake in northwestern China. The strain was genetically similar to one found in healthy migratory ducks at Poyang Lake in southeastern China, indicating that migratory birds have the potential to carry the virus as they travel. However, the study also found distinct regional viruses, suggesting that transportation of poultry plays the primary role in the spread of the virus within China.

So far there does not appear to be widespread transmission of the virus along migratory bird routes, and outbreaks have been isolated. Tests of migratory birds show that high pathogenicity H5N1 is uncommon. Only 6 of more than 13,000 healthy wild birds in China have tested positive, and none of 100,000 birds tested elsewhere have been found with the virus.

Should wild birds be culled?

No. Culling wild birds is unlikely to stop the spread of disease. Draining wetlands is completely unwarranted and could increase the dangers for wild birds by taking away important refuge areas, causing them to become more stressed and susceptible to disease, and to disperse, bringing the virus to new areas.

Is it safe to watch birds and feed birds?

Yes, it is safe to keep birding, to attract and feed birds, and to monitor nest boxes. The H5N1 virus has not been detected in North America, and even in areas with the virus, there have been no documented cases of wild birds infecting humans. As always, wash your hands thoroughly after handling bird feeders, bird nests, birdbaths, or water contaminated by birds. Avoid touching bird droppings or dead birds. If you must move a dead bird, use disposable gloves or double plastic bags. These precautions will help keep you safe from harmful bacteria and viruses including high pathogenicity H5N1, should it arrive among our backyard birds.

For more information about avian flu, please visit www.birds.cornell.edu/birdflu.

For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: lle24@cornell.edu