Japan confirmed its fourth case of the H1N1 virus yesterday in a teenager who recently returned from a school trip to Canada with the three other Japanese who have contracted the new flu strain. In the US, a man in Washington state with H1N1 influenza died last week, health officials said, the third US death among 2,200 confirmed cases in the country.
Worldwide, health officials said the true number of cases could be underestimated. Although most cases are mild, the virus has killed just as seasonal flu does.
Forty-eight people have died in Mexico and one each in Canada and Costa Rica.
The fourth Japanese patient, who was not identified, is being quarantined at a hospital near the airport, the Japanese Health and Welfare Ministry said. He had been in Oakville, Ontario, since April 24 and returned on Friday on a Northwest Airlines flight from Detroit, Michigan.
Japanese authorities have been busy tracking travelers who arrived on the same flight as the four confirmed to have the virus.
China and Hong Kong said they had quarantined travelers who were on the flight and had continued on to their countries. Hong Kong is keeping two people under observation who have not shown any flu symptoms. China’s Health Ministry said it had placed seven people under observation. Their conditions were not immediately known.
In Japan, medical staff wearing masks and rubber boots have been sent to major airports to isolate anyone suspected of being infected.
In the US, a man in his 30s with underlying heart conditions died last week, Washington Governor Chris Gregoire said on Saturday, describing his death as “a sobering reminder that influenza is serious.”
The virus has moved into the southern hemisphere, where influenza season is just beginning, and could mix with circulating seasonal flu viruses or the H5N1 avian influenza virus to create new strains, health officials said.
“One of the big challenges with influenza viruses is the way that they change, the way they combine and their prevalence in a number of species,” Anne Schuchat of the US Centers for Disease Control and Prevention told a news briefing on Saturday. “This is why it is so important for countries to have a strong capacity to deal with influenza and also why it is very important to understand what happens at the interface between people and animals.”
“Today there are almost 3,000 probable and confirmed cases here in the United States,” Schuchat said. “The good news is we are not seeing a rise above the epidemic threshold.”
Japan reported four cases and globally officials reported more than 4,200 people in 30 countries had been ill. Australia reported its first case, a woman who had been travelling in the US, but officials said she had made full recovery.
“We think this virus is in most of the United States,” Schuchat said. “The individual numbers are likely to be a very great underestimate.”
More Americans are seeing doctors for influenza-like illnesses at a time of year when such visits usually decline.
Schuchat said tests showed they did not all have the new H1N1 virus. Many have seasonal flu — the H1N1 seasonal strain, the H3N2 seasonal strain and influenza B — and other infections.
Seasonal flu kills between 250,000 and 500,000 people globally and infects up to a third of the population each year.
Health experts have not openly criticized efforts by other countries to stop the virus from getting in — most notably China and Hong Kong, which have quarantined travelers in contact with patients.
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