Why Humans Cannot Spread And Catch Bird Flu Easily

Last Tuesday, ABC presented a prime time made-for-television movie about Avian Flu, "Fatal Contact: Bird Flu in America",For those who missed it, you can read an outline on http://abc.go.com/movies/birdflu.html which tells of an American businessman on a trip to numerous destinations in the orient when the Chinese health authorities release - too late - information about a new strain of Avian Flu which quickly turns into a pandemic.  It's a movie, not a documentary; a work of fiction designed to entertain and not a factual accounting of a real world event.     

 There is no influenza pandemic in the world at this time. It is important to remember that H5N1 avian influenza is almost exclusively a disease of birds. The few human fatalities have come from close contact with, or eating affected birds. The H5N1 virus has not yet appeared in the U.S., but the appearance of the virus in the US does not mean the start of a pandemic. Remember, although we had a severe pandemic with great loss of life in 1918, flu pandemics in 1958 and 1969 were substantially less severe than the movie depicts. In fact, many Americans at that time did not distinguish the '58 and '69 pandemics from seasonal influenza and were unaware that a pandemic was underway. There is really no way to predict the severity of an outbreak until the symptoms and methods of transmission have been analyzed.

While the movie does serve to raise awareness about avian and pandemic flu, it should inspire preparation - not panic. Steps we can all take to prepare. Keep a supply of food and medicines on hand in case you have to stay home, you can practice good public health measures like frequent hand washing and staying home when sick. Additional good information is available at www.pandemicflu.gov.

The H5N1 bird flu virus strain does not settle in the upper respiratory tract, like the human flu virus does. H5N1 settles in cells deep within the lungs (deep down). This gives us humans two advantages:

1. If I have bird flu and sneeze, hardly any viruses will be sent out because they are deep down in my lungs. With the normal human flu virus, which settles in the upper respiratory tract (nearer my throat), a sneeze will send viruses out in the air and infect people around me.

2. If the virus needs to settle deep down in my lungs before making me ill, I need to be in an environment where lots of them are around me. Huge clusters of H5N1 viruses need to be around me for some of them to have a chance of getting way deep down into my lungs. Basically, I have to surround myself with lots of sick birds and stay very close to them for a long time.

To recap: Humans need lots of bird flu viruses around them to get ill. Infected humans expel tiny amounts of the virus.

This news explains why humans cannot catch bird flu from birds easily, and cannot spread it to other humans (unless you are next to a sick person all day - even then the chances are very remote). Hundreds of millions of birds have died as a result of H5N1 infection since 2003, but only 103 humans.

A study explaining this in detail can be read in the March 23 issue of Nature. It was carried out by researchers at the University of Wisconsin and the University of Tokyo.

The part of the lung the H5N1 virus strain infec