Flu Time

Hot topic - Avian flu ( bird flu )

According to BUPA (an international health and care company with bases on three continents and more than seven million customers. ):

written by BUPA's Health Information Team

A number of Asian countries have been affected by avian flu (bird flu) infecting their poultry stocks. In some of these countries, a small number of people have contracted the avian flu virus from chickens.

Scientists are concerned by these events because it is feared that the avian flu virus could merge with a human flu virus. The result of this merging might result in a new, highly infectious, rapidly fatal flu virus. Such a new virus would be transmitted rapidly from person to person with potentially devastating results.

To keep the outbreak of avian flu virus under control, many of the Asian countries are culling their poultry stocks to prevent further spread of the virus.

What is avian flu?

Avian flu is used to describe the influenza viruses that infect birds - for example wild birds such as ducks and domestic birds such as chickens. In fact, birds appear to a natural reservoir of flu viruses - 15 subtypes influenza A virus are known to be circulating in bird populations.

Many forms of avian flu virus cause only mild symptoms in the birds, or no symptoms at all. However, some of the viruses produce a highly contagious and rapidly fatal disease, leading to severe epidemics. These virulent viruses are known as "highly pathogenic avian influenza" and it is these viruses that cause particular concern. One such avian flu virus is currently infecting chickens in Asian countries.

Why are scientists and governments so concerned about avian flu?

Until 1997 avian flu was believed to only infect birds, however in 1997 it was discovered that the virus can occasionally infect people who have been in close contact with live birds in markets or farms.

This rare ability of avian flu viruses to infect humans (known as "species jumping") throws up a worrying possibility. It is possible that a highly pathogenic avian flu virus could merge with a human flu virus and create a new virus that could be easily passed between humans and was rapidly fatal. If this happens, the result could be the next flu pandemic.

What is a flu pandemic?

When a new, highly infectious form of a flu virus is formed it can rapidly infect a large number of people. The result is a illness that rapidly spreads round the world and may cause widespread loss of life. An example is the Spanish flu pandemic of 1918-1919 which caused an estimated 40-50 million deaths worldwide.

How would an avian flu virus merge with a human flu virus to produce a new, highly infectious flu virus?

There are two circumstances in which an avian flu virus could merge with a human flu virus:

In humans - if a person who already has flu is comes into close contact with birds who have highly pathogenic avian flu, there is a tiny chance that the person could become infected with the avian flu virus. If this happens, the person would now be carrying both the human flu virus and the avian flu virus. The two viruses could meet in the person's body and swap genes with each other. If the new virus had the avian flu's genes that made it rapidly fatal and the human flu's genes to allow it to be passed from person to person, a flu pandemic could result.

In pigs - pigs are susceptible to both human and bird flu viruses. If a pig became infected with both viruses at the same time, it could act as a "mixing vessel", allowing the two viruses to swap genes and produce a new virus.

Has such a new flu virus happened yet?