Spread of bird flu

According to a latest WHO report, environmental sources of the H5N1 bird flu virus may play a role in its transmission to humans. Highly pathogenic influenza A (H5N1) viruses are entrenched among poultry in parts of Asia, Africa and perhaps the Middle East. This has prompted the slaughter of hundreds of millions of chickens in these areas. Recently, the WHO team reviewed all known human cases of avian influenza, which has infected 350 people in 14 countries and killed 217 of them since 2003. In this review published in the New England Journal of Medicine, it was found that in 25 percent of cases there is no clear explanation about the source of exposure, and environment to human transmission remains a possibility. Most infections in humans are passed directly from birds to people, and very rarely one-person can infect another. From the small particles of virus-contaminated fluid stuck to surfaces to perhaps the fertiliser made from infected bird faeces, environmental factors are believed to carry the virus into people's noses or mouths. It is said that after exposure to infected poultry, the incubation period generally appears to be 7 days or less, and in many cases this period is 2 to 5 days. As compared to this, in cases of human-to-human transmission the incubation period appears to be approximately 3 to 5 days, although in one cluster it was estimated to be 8 to 9 days. With the increasing number of people getting infected with bird flu (or avian flu), WHO fears that the virus can mutate into a strain that passes easily from one person to another, setting off a pandemic that could kill millions of people in a couple of months.