Key questions answered by Seán MacConnell.
Q: What is bird flu?
A: The term "bird flu" describes one of several influenza viruses that birds can carry. Several types can also infect humans. These are different in make-up from the usual human flus.
Q: Can humans get it?
A: The authorities believe there have been cases of humans contracting bird flu primarily from contact with excretions from infected birds. Common victims are people who handle poultry on farms or at live markets. There is one known case of it spreading from one person to another. If poultry is properly reared and cooked, humans will not get the disease from eating fowl.
Q: Why is avian flu in the news now?
A: A particular type of bird flu, known as H5N1, is seen as a candidate to cause a flu pandemic if it mutates into a form capable of spreading easily from person to person. Because people have not developed immunity to H5N1, unlike the usual strains of human flu, it could have more severe effects on a greater scale. H5N1 has jumped the species barrier, causing severe disease in humans, on two occasions in the recent past and is now doing so again, in gradually growing numbers in Vietnam and Thailand and more than 60 people have died.
Q: Does human infection with H5N1 happen often?
A: No. Only very rarely. The first documented human infections with the H5N1 avian strain occurred in Hong Kong in 1997. In that first outbreak, 18 persons were hospitalised and six of them died. The source of infection in all cases was traced to contact with diseased birds on farms (one case) and in live poultry markets (17 cases).
Q: Why the panic?
A: Because the World Health Organisation (WHO) says that all available evidence points to an increased risk of transmission to humans when outbreaks of highly pathogenic avian H5N1 influenza are widespread in poultry. As the number of human infections grows, the risk increases that a new virus subtype could emerge, triggering an influenza pandemic. This link between widespread infection in poultry and increased risk of human infection is being demonstrated now in Asia.
Q: Is it reassuring that so few human cases have occurred?
A: Yes. The WHO has some evidence that the H5N1 strain may have been circulating in birds since April 2003. The detection so far of only a few human cases suggests that the virus may not be easily transmitted from birds to humans at present. However, the situation could change quickly, as the H5N1 strain has been shown to mutate rapidly and has a documented propensity to exchange genes with influenza viruses from other species.
Q: Is there a vaccine for bird flu?
A: Yes. French vaccine maker Sanofi-Pasteur has begun production of a vaccine against H5N1, but researchers have not settled on how large a dose will ensure protection and a world shortage of the vaccine is predicted. If bird flu began spreading widely, scientists would have to check whether that vaccine still would provide protection, or whether a new one would be needed.
Q: How is bird flu treated?
A: Two drugs that fight regular flu, Tamiflu and Relenza, are considered to be effective in treating flu caused by H5N1 if administered quickly. They also may help prevent infection. The Government plans to stockpile tens of millions of Tamiflu pills, and a smaller supply of the inhaled drug Relenza.
Q: Can the spread of the bird flu be stopped?
A: Because it is spread mainly by migratory birds, it will be difficult to stop the spread of the disease in birds. However, if countries move fast and destroy infected flocks, the disease can be controlled on the ground.