W.H.O. to Rewrite Rules for Declaring a Pandemic
In Tokyo, schoolchildren visited the upper house of Parliament on Friday. According to data from the World Health Organization, Japan has had 294 confirmed cases of swine flu, but no deaths.
Bowing to pressure, the World Health Organization announced Friday that it would rewrite its rules for alerting the world to new diseases, meaning the swine flu circling the globe will probably never be declared a full-fledged pandemic.
Dr. Keiji Fukuda, the deputy director general making the W.H.O. announcement, said that he could not predict exactly what the new rules would be but that criteria would include a “substantial risk of harm to people,” not just the geographic spread of a relatively benign virus.
The six-point system was created in 2005 when the threat was H5N1 avian flu, which has a fatality rate of about 60 percent. But the system does not take into account a virus’s lethality, and in the current outbreak, some countries have complained that the warning system created panic and pressure for border closings, even though the strain was less deadly.
Asked if the W.H.O. could damage its credibility by changing the rules in mid-outbreak, Dr. Fukuda said: “There’s nothing like reality for telling you whether something is working or not. Rigidly adhering to something that is not working would not be very helpful.”
Speaking in Geneva, Dr. Fukuda added, “We’re trying to walk a fine line between not raising panic and not being complacent.”
The W.H.O., starting in April, quickly raised its alert level to 4 and then 5 as the virus spread in North America. But even as the virus infected people in Britain, Spain and Japan, the agency did not go to Level 6, which signifies spread to a new continent. Dr. Fukuda argued that there was still no proof of “community spread,” meaning beyond travelers, schools and contacts. Some experts were skeptical.
While acquiescing, he noted that experts hashed out these issues in 2005. Geographic spread is easy to detect, but severity is highly subjective. Death rates are impossible to calculate before many people are infected; if they turn out to be high, precious time has been lost. Viruses can mutate, becoming more lethal, and even a less lethal strain can kill many people in poor nations with young, malnourished and AIDS-infected populations.
Separately, federal health officials said a study of flu genes released Friday showed that the virus could have been circulating undetected in pigs for years, and called for better surveillance.
The study, published online by Science magazine, was a collaboration between virologists from the Centers for Disease Control and Prevention and the W.H.O., along with others from Mexico, Britain, the Netherlands and the health departments of several American states and New York City.
After sequencing virus genes from 76 Americans and Mexicans and comparing them to known human and pig sequences, the study found no identical matches but concluded that the virus could be in pigs anywhere in the world, said Dr. Nancy Cox, chief of the federal agency’s flu division.
The closest match, surprisingly, was found in Thailand in 2005 — a pig with both North American and Eurasian flu genes.
Since the outbreak began, virologists have wondered how Eurasian genes got into a North American pig. Live pigs are moved through the Americas fairly easily, but rarely are legally moved across oceans, because they carry diseases. Even a single breeding boar must be tested and quarantined.
Now that the mixed genes have been found in Asia, it is possible that they came from a North American pig that was taken there. There is little flu surveillance of pigs in much of the world, and even in the United States it is “not very systematic,” Dr. Cox said.
Canadian pig farmers are required to report flu; Americans are not. Early this month, the United States Agriculture Department’s chief veterinarian said it sequenced only 500 samples a year from 100 million pigs.
In 2006, facing the avian flu threat, the United States chicken industry began voluntarily testing 1.6 million chickens a year.
Dr. Paul Sundberg, head of science for the National Pork Board, said it was planning more tests, especially on pigs in contact with people at fairs or livestock exhibits.
Henry L. Niman, who runs a Web site tracking flu mutations, complained that many swine sequences are posted by American universities and in Mexico only on private databases. “Those sequences would be very useful for figuring out how the H1N1 emerged,” he said.
The flu could also be in an intermediate host, said Dr. Cox, as the 2002 SARS virus passed from bats to humans through palm civets. But she said scientists “don’t have a hypothesis for alternative hosts.” Not enough is known about how many species carry flu, Dr. Cox said. For example, virologists were surprised to learn in 2004 that bird flu could kill zoo tigers and house cats.
Dr. Fukuda also said the new virus has been confirmed in 42 countries and had killed 86 people. About half of those hospitalized are young and healthy with no underlying conditions, he said. In the United States, such conditions are more common among the 300 now hospitalized.
Denise Grady contributed reporting.