A potentially virulent new strain of influenza virus has been isolated in a child in Hong Kong who died of the illness. Experts, however, say the strain is unlikely to present problems during our own wintertime flu season.
The virus was isolated last May in a three-year-old boy, who died of acute respiratory illness. The strain involved typically occurs in ducks, chickens and other birds, but had not previously been isolated in humans, according to specialists at the Centres for Disease Control and Prevention in Atlanta, Georgia.
The possibility that this new strain could cause widespread infection among humans was highlighted in the current issue of the science journal Nature. New flu viruses emerged to cause acute illness and many deaths during outbreaks of the Spanish flu in 1918, the Asian flu in 1957 and the Hong Kong flu in 1968.
New viral forms can cause significant acute illness because the population has little immunity to them, says Mr Seamus Dooley, laboratory manager at UCD's Virus Reference Laboratory. They are also dangerous because health officials might not have vaccines for the viral form responsible for a new outbreak.
The new strain did not seem to be moving through the population, however, and only one case had been detected, Mr Dooley said. "It doesn't seem to have person-to-person transmission," he said. "I am not saying that we should be smug about it," he added, but the new form did not appear to be spreading.
"The Hong Kong flu case had the potential for a high rate of infection. However there has been no evidence of onward infection" from the initial case, according to Mr Simon Barber of the UK's Public Health Laboratory Service, which monitors the rise and fall of flu case numbers. The World Health Organisation had not yet detected any further cases involving this new strain.
Several species, including humans, pigs, horses and birds were affected by their own distinct type of flu virus, Mr Dooley explained. Occasionally viruses would "jump" between species or combine with other viral types to form wholly new viruses.
These new forms always had the potential to cause pandemics but seldom did, he said. Health authorities in the northern hemisphere watched each year for what types of flu emerged during the southern hemisphere winter. This allowed the preparation of flu vaccines for the flu types most likely to occur during our wintertime influenza season.
