A. I recently attended a lecture about avian influenza, aka bird flu. Before this I thought the disease was a non-issue for us Californians. Apparently, this probably is not to be the case.

We keep hearing that avian influenza (AI) may cause a "global pandemic." A pandemic is a disease that spreads around the world from person to person and kills lots of people. The Spanish flu of 1918 was a global pandemic caused by AI that killed 20 to 50 million people worldwide. Fortunately, disease prevention and treatment has come a long way since then.

So what is AI? It's an influenza virus that circulates in birds just like the influenza virus that hangs around in people. There are different strains, just like human influenza (which is why you have to get a new flu shot every year). Most bird strains cannot infect humans. However, strains can change, or mutate over time to infect other species and/or become more deadly.

The strain of AI that is of concern now is called H5N1. This strain is able to infect people. It is passed through secretions and excretions from infected birds. H5N1 first crossed from poultry to humans and caused deadly, though small, outbreaks in Hong Kong in 1997 and in 2003.

H5N1 is a nasty strain because it kills birds and people. Since 2003 the current outbreak has infected 169 people with 91 deaths — a 54 percent mortality rate. Granted, many of the affected so far have been poultry industry workers. But we can't get too comfortable because the H5N1 strain is able to mutate easily. We first identified it in commercial poultry flocks, but it has made the jump to people and more recently to wild birds.

We care about AI in wild birds because wild birds have the potential to carry the disease around the world via their migratory patterns. From Southeast Asia the H5N1 strain has spread to Europe and recently Nigeria. The only possible explanation is that it is being carried by migratory birds, in particular waterfowl. Because the Pacific migratory routes include California, it is possible that we will be seeing the disease here soon. Also of interest is the fact that while most poultry AI is not lethal to wild birds, the H5N1 strain has become deadly to wild birds, indicating another mutation.

The mutation we worry about the most is the one that would cause the virus to be passed from person to person. That is what happened with the Spanish flu in 1918. It also happened in the 1957 (Asian flu) and 1968 (Hong Kong flu) pandemics. If the virus mutates in that way, the potential for a pandemic will be much greater. That is why experts around the world are watching this disease so carefully.

California is stepping up its surveillance for AI and will soon begin testing migratory birds. At this point, there is no reason to think that a dead wild bird in your backyard has AI. (In fact, birds dead longer than four hours cannot even be tested for the disease.) However, the CDC does have some recommendations:

• Do not handle wild birds. Wash thoroughly with soap and water if contact occurs.
• Hunters, in particular hunters of waterfowl, should not eat or handle sick game, should wear gloves when cleaning or handling birds and should cook all meat thoroughly.
• Report dead birds to the local Department of Fish and Game.