By BETSY MCKAY
New reports showed the A/H1N1 swine flu had spread to 18 countries, as the World Health Organization moved closer to officially declaring the new strain a global pandemic.
Incidents of the new flu continued to turn up, including in a herd of swine in Canada, U.S. officials said. But health officials cautioned that declaring a pandemic doesn't mean the disease, which has proven mild outside of Mexico, is deadly to most people or will sweep the entire globe.
"There is a lot of misunderstanding in terms of fear and death," said Margaret Chan, director-general of the WHO, in an interview. Declaring a pandemic "doesn't mean death in big numbers is going to happen."
Last week, concerns about a deadly flu swept the world. Mexico, where 19 deaths have been blamed on the virus, shut schools and discouraged public gatherings. In Hong Kong, 300 guests and staff at one hotel were quarantined after a Mexican visitor tested positive for A/H1N1. Cases were reported across the U.S., from New York to Sacramento, and some schools were closed, though by the end of the week most of the evidence suggested that most symptoms were mild.
Unease in the agriculture sector, particularly in the pork industry, was amplified by the weekend discovery of the flu in a swine herd in Canada, which raised the specter of a new avenue of transmission to humans. The infected herd was quarantined and the source of the virus was determined to be a worker recently returned from Mexico, officials said.
Officials have emphasized that people can't get the flu by eating pork products. Global transmission of the disease is the subject of intense research by scientists from the WHO, the Atlanta-based Centers for Disease Control and Prevention and other agencies and governments.
The challenge for all of them has been to balance the genuine danger of a serious outbreak with the risk of overreacting, a decision that must be made before the virus's full lethality becomes clear.
"We cannot overreact and we cannot be complacent either," Dr. Chan said. "We haven't seen the full spectrum of the disease.... One thing I have learned is that with any new disease, they're unpredictable."
Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the WHO and CDC have been consistent and on target with their messages, stressing the disease needs to be taken seriously because it's new and it isn't clear yet how lethal it might eventually be. "It's the media that has really created the roller coaster in terms of over- and underreacting," he said.
Dr. Chan said she couldn't say when the WHO, a United Nations agency, would raise its alert level to phase 6, which signals all public-health authorities in the world to activate their pandemic-preparedness plans. The agency declares a pandemic when community outbreaks are occurring in two countries in one region of the globe and at least one country in another region. This would be the first flu pandemic since 1968.
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The A/H1N1 strain had been reported in 18 countries and sickened 898 people as of Sunday, according to the WHO, which counts only cases that have been confirmed by a laboratory test. Those cases include 506 infections in Mexico, with 19 deaths -- far fewer than Mexican authorities originally indicated. The U.S. has reported 226 infections in 30 states and one death.
The disease is spreading within communities in the U.S. and Mexico, and case counts are mounting in Canada. Health officials have said community outbreaks could occur in other countries where case counts are fairly large, such as Spain and New Zealand. The WHO has lifted its global pandemic alert level twice in the past week, to phase 5 from phase 3.
Dr. Chan said the WHO acted appropriately in raising a global alarm over the new strain, given its unpredictability after it emerged at the tail end of this flu season. An initial outbreak of flu in spring 1918 was followed by a second, far deadlier wave months later that killed millions of people around the world, she said. "It may come back," Dr. Chan added. "The world should prepare for it."
But a pandemic declaration "doesn't mean every country in the world will be affected by this wave of infection," Dr. Chan said. "We know fully from the data that most people make a full recovery and some people don't even need to take medicine." The new strain of A/H1N1 flu could remain mild or morph into a deadlier bug, so public health authorities must respond aggressively, she said.
Since being named to head the WHO in 2006, Dr. Chan has overseen the implementation of new international rules compelling countries to notify the agency quickly about outbreaks and other public health occurrences, instead of shielding threats from the outside world as China was accused of doing when SARS spread in 2003. Dr. Chan was director of Hong Kong's health department when SARS and H5N1 avian flu struck.
In recent years, the WHO has pushed countries to develop plans to contain outbreaks and has stockpiled antiviral drugs. The Geneva-based agency now tracks outbreaks in real time instead of scanning dated reports and trying to get besieged country health officials on the phone.—Lauren Etter, Scott Kilman and Peter Stein contributed to this article.
Write to Betsy McKay at email@example.comPrinted in The Wall Street Journal, page A14