October 17, 2025
2 minute read
Flu cases surge in Japan, sparking global health concern
School closures and hospitalizations due to an unexpected early surge in flu cases in Japan have experts worried about what lies ahead for other countries.
Paulo Friedman/Contributor/Getty Images
Japanese health authorities have declared a flu epidemic in which thousands of people have become infected with the respiratory virus. The number of infections is unusual for this time of year and could lead to outbreaks in countries in Asia and Europe heading into winter, although it is unlikely to become a global pandemic, the researchers said.
As of October 10, Japan has reported 6,013 cases of influenza virus infection. More than 100 schools closed, and nearly half of the 287 people hospitalized due to the flu in September were children 14 or younger. On October 3, the Ministry of Health, Labor and Welfare declared a nationwide epidemic. Outbreaks are classified as epidemics when the number of infections exceeds what is expected in a given area over a period of time.
Influenza virus outbreaks typically occur seasonally every yearmainly in winter in countries with temperate climates. In Japan this usually occurs around the end of November. This year, the rise in the number of people being treated for flu began five weeks earlier than usual, says Vinod Balasubramaniam, a molecular virologist at Monash University Malaysia in Subang Jaya.
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In the past few years, the flu season has started early in Japan, but not that early, says Ian Barr, a researcher and deputy director of the World Health Organization Collaborating Center for Influenza Reference and Research, based in Melbourne, Australia. “You may see cases in October, but not epidemic-type numbers,” Barr says.
Increased international travel since COVID-19 pandemic “This is one of the factors that can cause the flu season to start early,” says Balasubramaniam. Other factors include climate change and lack of exposure to the circulating virus, especially among older people and young children.
Information has not yet emerged about which strains are circulating in Japan, but Barr says outbreaks there may be caused by a strain of influenza A called H3N2, which has surged in Australia and New Zealand over the past two months, coinciding with the end of winter in the Southern Hemisphere. People from Australia are traveling to Japan in huge numbers, meaning there is a greater chance of transmission of the virus between hemispheres, he said.
Not a throwaway
Other countries, including Malaysia, have also seen early flu seasons this year in which the H3N2 strain has predominated, Balasubramaniam said. According to the data, about 6,000 schoolchildren across Malaysia have been infected and some schools have been closed. Reuters. Australia and New Zealand also saw early spikes in flu cases, with different strains dominating the outbreaks, Barr said.
According to him, the current flu epidemic in Japan is unlikely to develop into a global pandemic, given that countries in the Southern Hemisphere are now experiencing warmer seasons, which reduces the spread of the virus. “But it could very well leave Japan and spread to other neighboring countries or countries that are on the travel route from Japan,” Barr says. Countries approaching winter will be more susceptible to outbreaks.
This article is reproduced with permission and has been first published October 14, 2025.
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