The number of swine flu cases in Japan are escalating with surprising speed, and health officials are not sure why. The Japanese government on Wednesday confirmed the first two cases of the disease in Tokyo, the world’s most populous metropolitan area. Meanwhile, the number of Japanese who have contracted the new flu has more than doubled since May 18 from 130 to 279, a rate of increase that is “without a doubt” the highest in Asia, says Peter Cordingley, regional spokesman for the World Health Organization. “It’s explosive.”
Since May 16, when Japan confirmed its first instance of the flu being transmitted among the domestic population, the virus has hopscotched through the western prefectures of Osaka and Hyogo, where more than 4,400 schools and some businesses have been temporarily closed. Initially, efforts to contain the disease which included the establishment of a special committee chaired by Prime Minister Taro Aso appeared to be successful. But now that the virus has reached the greater Tokyo area, home to 35 million, concerns are growing over the speed of transmission.
The majority of the confirmed infections are among high school students. “These are the kinds of people who meet in cafeterias, sports events, youth clubs, karaoke,” says Cordingley. “They mingle a lot, and mingling is the perfect environment for this virus.” But he added that “We honestly don’t know” why the number of infections have jumped. “It’s all happened since Saturday.” so far, none of those who have contracted the disease in Japan have died.
Health authorities believe the Tokyo patients, two 16-year-old girls who attend the same private high school, contracted H1N1, the swine flu virus, while participating in the Model United Nations at the United Nation’s headquarters in New York City. The two roomed together and sat next to each other on a Continental airlines flight that returned them to Narita International Airport on May 19. One girl, from the Hachioji district in western Tokyo, was feverish on the flight but a quarantine test showed her to be negative for the new flu. A test taken Wednesday night at a Hachioji hospital confirmed H1N1. Her classmate, who is from Kawasaki, south of Tokyo, was confirmed with the swine flu the same night.
Governments worldwide have tried to contain the spread of the flu that has already infected more than 11,000 people in 41 countries, killing 85. Experts say H1N1 is mildly virulent and comparable to that of seasonal flu, but very contagious. “We have no way of forecasting what’s going to happen in Tokyo. But it’s going to happen, and it’s going to happen big time,” says Cordingley. A major concern expressed by the WHO is that even if the number of new flu cases flattens out as the end of the flu season nears, another more virulent strain of the virus could return this winter.
Public service announcements being broadcast on Japanese national television feature Aso urging the public to keep calm. Sales of medical masks have skyrocketed and masks are commonly being worn by commuters. Visitors to offices in Tokyo’s financial center of Marunouchi as well as those entering the parliament building are now required to sanitize their hands and don masks. The chief economist at a major bank says his colleagues have canceled meetings with business associates who have arrived from abroad within the past five days.
On Friday morning, the government is expected to adopt a set of guidelines to fight the flu at the recently established Headquarters for Countermeasures Against Influenza A in Tokyo. The new guidelines will be a modification of an existing plan created to counter the more virulent H5N1 virus, known as avian flu.
With reporting by Yuki Oda
See 10 things to do in Tokyo.
See TIME’s Pictures of the Week.