Japan’s health authorities have declared a nationwide influenza epidemic after flu cases surged far earlier than usual, marking the country’s second-earliest outbreak in two decades. The Ministry of Health, Labour and Welfare made the declaration on October 3 after influenza cases exceeded epidemic thresholds five weeks ahead of the typical flu season.
Between September 22 and 28, more than 4,000 people in Japan were treated for influenza—an average of 1.04 patients per monitored medical institution. That figure jumped to over 6,000 cases the following week, or 1.56 patients per institution, more than double last year’s rate. The outbreak has forced 135 schools and childcare centers across the country to temporarily close, three times higher than during the same period in 2023.
Twenty-eight of Japan’s 47 prefectures have reported rising flu cases, with Okinawa recording the highest infection levels. Health officials say the early onset may be linked to increased travel and tourism following the pandemic.
The outbreak is part of a broader regional trend. Rising influenza cases have also been reported in Singapore, Thailand, and India in recent weeks. India’s northern states have seen a spike in infections caused by the H3N2 strain—a descendant of the virus behind the 1968 Hong Kong flu pandemic.
Experts warn the early start to flu season may signal shifting global disease patterns. “The flu season has started really early this year, but in the changing global environment this might become a more common scenario,” said Professor Yoko Tsukamoto from Japan’s Health Sciences University of Hokkaido.
In Singapore, health authorities have reported an increase in acute respiratory infections, with flu cases up by as much as 40% last month, according to DoctorAnywhere, a medical network. Although most infections remain mild, doctors say changing weather patterns and frequent thunderstorms during the inter-monsoon period may be contributing to the rise as people spend more time indoors.
Thailand has also warned of a major surge, with more than 555,000 flu cases and 59 deaths recorded so far this year. Heavy rainfall during the monsoon season and climate-related extreme weather are believed to be influencing transmission.
Researchers say climate change could alter the behavior of flu viruses and human exposure patterns. “With increased rainfall and higher population densities, we may actually observe an increase in influenza across all climates,” said Dr. Sophie Dennis of the World Health Organization.
Virologists also caution that new virus strains may be emerging. “There are drifted influenza strains circulating, which we may not be immune to,” said Dr. Paul Tambyah, former president of the Asia Pacific Society of Clinical Microbiology and Infection.
While scientists stress there is no sign of an imminent pandemic, they are closely monitoring viral evolution in both humans and animals. As Tsukamoto noted, “We are seeing greater global movement of people—and the virus is moving with them.”
