As the northern hemisphere gears up for the annual flu season, another exotic strain of the disease has turned up in Hong Kong. Although health officials are anxious not to cause panic, the Hong Kong strain is being monitored closely because it seems to have jumped from pigs-the animals thought to have been the origin of the 1918 Spanish flu pandemic that killed an estimated 20 million people worldwide.
New strains of flu turn up each year. Most are variants of existing viruses and so pose no special problems. But every few decades, a radically different virus comes along, triggering a pandemic that can kill millions across the globe; the last two were in 1957 and 1968. These killer strains are thought to come from either pigs or poultry.
The latest alarm was sounded after a 10-month-old girl was admitted to Hong Kong's Tuen Mun hospital in late September. Although she was successfully treated, her virus bears all the molecular hallmarks of a strain from pigs. The finding is worrying because analyses of preserved tissue from victims of Spanish flu suggest that it jumped from pigs to people (New Scientist, 29 March 1997, p 20).
"We're monitoring the case very carefully for that reason," says Alan Hay, director of the WHO influenza collaborating centre at the National Institute for Medical Research in London. Hay's team, and virologists at the US Centers for Disease Control and Prevention (CDC) in Atlanta, are now studying samples of the virus taken from the Hong Kong patient. "We don't know the ins and outs of this yet," says Hay. "It's at quite a preliminary stage."
Previous small outbreaks of swine influenza viruses in people caused what Alan Kendal of Emory University in Atlanta calls "false alarms". In 1986, a Dutch man suffered severe pneumonia after contracting a swine-type virus. And in 1977 a similar virus turned up in a handful of people in Fort Dix, New Jersey.
Neither of those viruses had the combination of virulence and high transmissibility needed to trigger a pandemic. And it may well be that the new Hong Kong virus presents no special danger. Kendal, who headed the CDC's influenza programme in the 1980s, says that health officials find themselves in a dilemma each time a virus crosses over from pigs. "The question is: how do you not cry wolf while avoiding closing the door after the horse has bolted?"
But given the obviously devastating impact of a flu pandemic, no one can afford to be complacent. A team at the CDC has predicted that the next pandemic could kill up to 200 000 people in the US alone (New Scientist, 24 July, p 5).
Hong Kong was the scene of a major flu scare two years ago, when a strain of flu from chickens struck 18 people, killing six of them. Fortunately, the outbreak was contained and there was no evidence of human-to-human spread. But in the wake of that scare, Peter Patriarca, a senior official with the US Food and Drug Administration who was responsible for drawing up an emergency action plan for the US in the event of a pandemic, warned that too few resources were being devoted to the project.
Even now, says Daniel Lavanchy, head of the WHO's influenza programme, only ten nations have produced pandemic action plans. "The next pandemic could begin anywhere at any time," says Martin Meltzer, a CDC official working on the US action plan. "We need better surveillance now, and it's not happening."
Author: Michael Day
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