Nature 427, 274 (22 January 2004); doi:10.1038/427274a
Bird flu sparks worldwide bid to prevent human pandemic
ALISON ABBOTT AND DAVID CYRANOSKI
The outbreak of highly contagious bird flu that is sweeping Asia, and which has killed at least five people, has put the World Health Organization (WHO) on full alert.
WHO scientists are now pulling out all the stops to trace the origin of the virus, known as H5N1, and to develop vaccine candidates. The spectre of a new human influenza pandemic, similar to that which killed millions in 1918, looms over their effort. Pandemics arise when bird or pig flu viruses jump the species barrier to humans and mutate into highly contagious forms.
The current bird flu outbreak, which has wreaked havoc among poultry in Vietnam, Japan and South Korea, is exceptionally worrying, says Albert Osterhaus, an influenza expert at Erasmus University in Rotterdam, the Netherlands. Bird flu outbreaks in the Netherlands and Hong Kong last winter were rapidly contained and led to the deaths of only three people (see Nature 422, 247; 2003). But Osterhaus says that management of the current outbreak has been loose and surveillance inadequate. There is no sign that the outbreak is abating, and it may already have spread to birds in Cambodia or Laos, where surveillance is also lax.
Viruses that jump the species barrier tend to be highly pathogenic, as the new host's immune system has had no time to build up defences. Although dangerous, the viruses are not necessarily contagious because they are adapted to survive in their original host. But the greater the number of people who catch the flu, the greater the chance that the virus will mutate into a form that is easily transmitted between humans. As yet, human-to-human transmission does not seem to have occurred.
Scientists in Japan, Hong Kong and the United States have sequenced the genomes of viruses found in birds in Vietnam, Japan and Korea, as well as those isolated from Vietnamese patients who have died.
The genomic data could reveal where the virus first emerged, its path of transmission and mutation rate, and how to control the spread, says Masato Tashiro, a virologist at the National Institute of Infectious Diseases in Tokyo. "The strains are similar to that isolated from a 2003 Hong Kong victim," he adds.
The data are being pooled in the Influenza Sequence Database based in Los Alamos, California, to aid development of human vaccine candidates. One candidate, made for the 2003 Hong Kong outbreak, is already being tested and if shown to be effective against the current strain will offer the effort a head start. "Should the few cases we are currently seeing in Vietnam turn out to signal a pandemic, we shall be ready for it," says Maria Cheng, a WHO spokeswoman based in Geneva. |
