Preparing for a pandemic influenza

Stephen D. Prior

An episode of pandemic influenza is the viral equivalent of a perfect storm. Three essential conditions must be met for an outbreak to begin: a new flu virus must emerge from the animal reservoirs that have produced and harbored such viruses-- one that has never infected human beings and therefore one for which no person has developed antibodies; the virus has to make humans sick (most do not); it must be able to spread efficiently, through coughing, sneezing, or a handshake. The avian flu virus H5N1 already has met the first two conditions: transfer to humans has been documented and the effects are deadly, with 30 percent to 70 percent lethality, but the transmission rates to humans and between humans are still relatively low. Recent reports suggest the virus is mutating and could change in ways that allow it to fulfill the third criterion. When the human-to-human transfer begins,...