July 2006
Explaining The Avian Flu By Rob Fergus

It is hard not to read the newspaper or watch television reports without becoming concerned about the spread of the avian influenza virus. Many people seem to be afraid they could contract the avian flu from birds in their backyard, so what do you as a garden center operator need to know and tell your customers about the relationship between bird feeding and contracting avian flu?

Having the right answers to your customers’ questions will help ensure, and hopefully increase, sales in the birding category.

What is avian influenza?

Avian (or bird) influenza is primarily a disease caused by several related types of viruses. Most of these viruses are usually only found in birds, while others, such as the common flu virus, can cause illness in humans and other mammals. While there are more than 100 different types (and even more subtypes) of avian influenza, the one news reports are concerned about is referred to as H5N1. This virus mostly attacks domestic birds like chickens, turkeys and ducks but has also reportedly killed more than 130 people around the world since 2003.

How does H5N1 avian influenza spread?

This virus is usually spread from bird to bird through close contact with nasal or other bodily secretions. It is especially easy to spread in factory farms where birds are in close contact with one another. The virus is difficult for humans to contract because large numbers of the virus are required for infection. It is also difficult for people to spread the virus to other humans because it lodges deep inside the respiratory system where it is harder to be coughed out and spread to others. So far, all human cases have come from people who have had close and extended contact with either infected birds or other infected people.

Do wild birds spread H5N1?

While many species of wild birds have been infected by H5N1, the virus most commonly infects water birds such as ducks and swans. Since many infected birds apparently die without spreading the virus to others, wild birds are more likely to be victims rather than transmitters. This past winter, some mute swans carried the virus from Eastern Europe to Western Europe, where they apparently died without passing it on to humans or other birds.

The only humans to contract the virus from wild birds were a handful of young women in Azerbaijan who illegally plucked and processed the bodies of several swans that died near their village. There is no evidence to suggest people can contract H5N1 from wild birds without such close and prolonged contact with the bodies or secretions of infected birds.

Is H5N1 coming to America?

Researchers are trying to better understand how the virus has spread across the eastern hemisphere. There is a small chance that wild birds from Asia could carry it to Alaska or Greenland, where it might spread south through contact with migrating birds. In the past, there has been only very limited exchange of different avian flu viruses between the hemispheres, so it is thought to be more likely that if H5N1 were to come to the United States, it would arrive by way of infected poultry or poultry products imported from another country.

Legal and illegal poultry trade is the primary way H5N1 has spread in the past. Globalization of trade has made it much more likely that H5N1 will eventually arrive in the United States, but biosecurity measures are in place to deal with the virus should it infect poultry operations here in the United States. Most wild birds infected with H5N1 die without spreading the virus to other birds; in the unlikely event that wild birds do carry the virus to the United States, it probably will not persist long in the wild bird population.

Does backyard bird feeding put people at risk?

No one has ever contracted avian flu from wild birds in their yards. The first thing to remember is that the dangerous H5N1 has not been found in North America. Even if the virus were to arrive in North America, it is mostly a disease of water birds and domestic poultry. The small birds in your backyard, even if they were to contract H5N1, could only spread it to humans if there were close and prolonged contact with infected birds.

However, anyone who comes into direct contact with birds and their droppings should follow recommended sanitary practices for those who handle birds (www.nwhc.usgs.gov/publications/wildlife_health_bulletins/WHB_05_03.jsp), and since birds can transmit other diseases to humans (e.g., salmonellosis), people who feed birds should routinely clean their feeders and birdbaths as recommended by Audubon (www.audubon.org) and the USGS National Wildlife Health Center (www.nwhc.usgs.gov).

By keeping bird feeders and birdbaths clean and by washing up thoroughly after servicing them, there is almost no way to contract H5N1. There is a much greater risk of tripping on your way out the door than there is of contracting avian flu or any other disease from backyard wild birds. The National Safety Council reports that trips and falls killed 16,000 Americans and sent more than 7 million others to the emergency room in 2003; less than 200 people across the globe have died from H5N1.

Will the H5N1 virus mutate and become more of a threat to people?

Viruses mutate and change all the time, but random mutations are just as likely to make H5N1 safer for people rather than more dangerous. Global health officials are monitoring H5N1 cases in humans and birds but have yet to find mutations that make it more easily transmitted from birds to people or from person to person. If the virus ever does mutate to become easily transmitted from person to person, then we will all be more at risk of contracting the virus from each other than from casual contact with birds in our backyards.

The best and latest information about H5N1 avian influenza can be found online at these Web sites:

Centers for Disease Control


GRAIN report on avian influenza and the global poultry industry


United Nations Food and Agricultural Organization


ProMED-mail Program for Monitoring Emerging Diseases


USGS National Wildlife Health Center


United States Fish and Wildlife Service


BirdLife International Statement on Avian Influenza


Wetlands International Statement on Avian Influenza


The National Audubon Society


Rob Fergus

Rob Fergus monitors the global avian flu situation for the science office of the National Audubon Society in Ivyland, Pa. He can be reached at [email protected]


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