bird flu, avian flu, pandemic

What is Bird Flu

Readers Question: What is Bird Flu?
BIRD FLU Humans have known and feared diseases caused by viruses for thousands of years. Among the diseases that viruses cause are infectious hepatitis, polio, rabies, and AIDS. It is easy to see why the late Sir Peter Medawar, Nobel laureate in physiology or medicine, wrote, A virus is a piece of bad news wrapped in protein. Perhaps the most lethal virus in human history has been the influenza virus. Some 21 million Americans and Europeans died of flu within 18 months in 1918 and 1919, an astonishing number. The recent outbreak in Hong Kong of a potentially deadly strain of flu has focused the world’s attention once again on flu.

A potentially deadly new strain of flu virus, A(H5N1), has emerged in the last few months, again in Hong Kong. Its arrival was greeted with unusual caution by scientists for two reasons. First, A(H5N1) represents a novel combination of H and N spikes, the sort of new combination that has in the past been associated with major flu epidemics. Second, unlike all previous instances of new flu strains, A(H5N1) passed to humans directly from birds, in this case chickens. A(H5N1) was first identified in chickens in 1961, and in the spring of 1997 devastated flocks of chickens in Hong Kong. The first human case of “bird flu” occurred in May, 1997, in a 3-year-old boy who died of the infection. The number of human infections by A(H5N1) remains small, with

17 confirmed cases by the end of the year. Five have died, and three more are in intensive care units, surviving with the aid of mechanical respirators.

Fortunately the bird flu virus does not appear to spread easily from person to person. Public health officials remain concerned that the genes of A(H5N1) could yet mix with those of a human strain to create a new strain that could spread widely in the human population. To prevent this, health officials have ordered the killing of all 1.3 million chickens in Hong Kong. Thousands of blood samples have been sent to the Center for Disease Control and other laboratories to determine the extent of the A(H5N1) infection among people, chickens and other animals in the Hong Kong area. Tests must be done carefully in high-level biosafety laboratories, as any one of the samples may contain infectious A(H5N1) virus.

No decision has been taken to produce a vaccine directed against the bird flu virus. Such a vaccine will not be easy to produce, as the virus kills the chicken eggs usually used to mass-produce flu vaccines. One approach being contemplated is to produce the vaccine from a similar (but not egg-killing) strain isolated from ducks in Singapore in 1997. Public health

scientists have injected the duck virus into laboratory ferrets, often used as test animals in flu research because they develop classic respiratory symptoms. Is the duck virus enough like bird flu that the ferrets develop antibodies that protect against A(H5N1)? It will take months to know.

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