Bird flu news: what factors encourage spread to humans in a bird flu outbreak?

27 March 2008

Researchers involved with the United Nations has just published research that tells us more about how bird flu virus spread in Vietnam and Thailand during the bird flu outbreak four years ago.

They identified three separate peaks of infection with the H5N1 bird flu virus and used computer models to study how the virus spread. Surprisingly, the number of domestic chickens that were kept by the local population was not the major factor that dictated how bird flu spread to people, causing some of their deaths.

Now, a few bird flu facts: In total, bird flu has claimed the lives of 236 people since the first outbreak was recorded in 2003. The deaths have occurred in 10 other countries apart from Thailand and Vietnam. So far, the bird flu virus has spread from birds or animals to people: there have been no confirmed accounts of the virus spreading directly from person to person. This reduces fears that there could be a bird flu pandemic that would sweep across the world, killing many people, as the flu pandemic just after World War I in 1918-1920. The symptoms of bird flu are severe - this is a very pathogenic flu virus that affects healthy young people and adults, with quite a high death rate.

The bird flu information from this study should be helpful in any future outbreaks of avian bird flu to be able to contain the spread of the disease more effectively. One suggestion is that satellite technology could be used to monitor duck populations and migrations and the extent of land covered by rice fields to predict where the greatest danger lies - this could be applied to Cambodia and Laos as well as other parts of Vietnam and Thailand.

This should help deploy bird vaccine in areas where it will do the most good - mass vaccination of birds is extremely costly and time consuming, and many birds are vaccinated without need.

Why are ducks so important? The research suggests that free range ducks may travel more widely within a local area, so becoming more exposed to infected birds. Domestic chickens tend to be kept in a smaller, more confined space, so don't represent such a source of human infection.

To date, the H5N1 bird flu virus has caused human disease only when it has passed to people from birds.The worry is that flu viruses are very quick to mutate - a mutation that enables the virus to pass from person to person directly could set off a global bird flu pandemic, which could kill millions.

The bird flu uk situation has never been as severe as in Asia, but the bird flu virus has reached the UK, and many domestic birds had to be culled in 2007 to stop the virus spreading.