The danger of bird flu The bird flu was first recorded to have been passed on to humans in 1997 in Hong Kong 1. The virus

        This has not happened yet although being a few cases of the virus spreading from human to human these were limited in scale. Health officials fear that the avian viruses will find a way of spreading easily among humans.

        This type of change in influenza viruses is known as an antigenic shift. This happens when an influenza virus subtypes to a virus which humans have little or no defence against, possibly causing a pandemic.

The virus is carried mainly in water birds. The bird hosts the virus in their intestine. It can be transmitted to other birds by saliva, nasal secretions and faeces. The most common way of the virus being transmitted is faecal to oral. Domestic birds can also get this virus from cages and bird feed if they are infected. Wild birds that have this disease do not normally suffer from it but can pass it on to other birds.

The global effort to avert the spread of bird flu is complicated, centring on the health of both birds and humans. Various ways of stopping the virus spreading between domestic birds have been carried out, such as culling. Since the first cases of humans being affected appeared millions of birds, mainly chickens have been slaughtered. Farms have been quarantined. Some have questioned the wisdom of destroying so many birds. The birds were either burned or buried alive. This is the WHO’s first line of defence against the spread of the avian viruses.

        Surveillance programs have also been used by some countries. All poultry has to be vaccinated and watched in farms and markets. Some are put into quarantine until they are deemed healthy. Farms also have to disinfect boots and tires.

        Other countries have banned or restricted the importation of birds and eggs from places with flu epidemics. The United States have banned the importation of birds from most Asian countries 6.

According to the WHO there have only ever been two cases of human-to-human transmission in Asia. Doctors and health officials in Vietnam insist that they have no evidence of any such cases. The WHO also suspect that it is, in fact, ducks, not chickens – the birds that have been culled, who are the main danger to the bird flu spreading as they carry the virus and hold no symptoms. The Vietnamese have killed 825,000 ducks, 470,000 chickens and 500,000 other fowl to prevent further spread of the virus. Health officials say that there have been no further cases since March 16th but they believe that it will come back 7.

        The vaccines the United States plan to test are thought likely to be ineffective. Even if the result of the vaccination proves positive they will still take too long to produce on a large scale. It will take far too long for enough doses to prevent a pandemic strain affecting humans. Other countries are following more promising approaches but are not ready to start testing them out. Because of the viruses’ capability of mutating and affecting humans, many countries have changed strategies. Instead of waiting for a pandemic strain to emerge human vaccines against the current strain are being created. Although these vaccines will not be perfect they are thought to make a difference between life and death. The sooner prototype vaccines are tested the sooner they can be manufactured and can help prevent the virus affect humans 8.

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7 – The times, April 17th

8 – New Scientist magazine, issue 2492