Riccardo Liguori With over 6,000 infections and 100 schools closed, Japan declares a national flu epidemic. Infectious disease specialist Bassetti warns: the H3N2 strain could reach Europe in the coming weeks
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Japan has declared a national influenza epidemic after cases surpassed 6,000, with over a hundred schools forced to temporarily close. A level of spread considered off the charts for this time of year: the flu season in the country typically only begins between late November and early December.
This year, however, infections increased as early as September, approximately five weeks ahead of schedule. Surveillance laboratories report an unusual pattern, likely linked to a combination of environmental and social factors.
An early start that surprises experts
Virologist Vinod Balasubramaniam from Monash University Malaysia explained to Nature that the early surge “has never been observed at these levels” and could be influenced by increased international mobility following the end of Covid-related restrictions, climate variations altering respiratory seasons, and lower natural immunity in children and the elderly, who have been less exposed to the virus in recent years.
According to epidemiologists, increased contact between regions and countries is shortening the distance between flu seasons in the two hemispheres, disrupting the traditional balance between the Northern and Southern worlds.
The role of the H3N2 strain
The virus under closest observation is the influenza A (H3N2) strain, already responsible for a sharp increase in cases in Australia and New Zealand during the austral winter. As Ian Barr, deputy director of the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne, emphasized, “it’s likely that circulation of the H3N2 strain has been accelerated by travel between hemispheres, particularly to Japan, where tourism has returned to pre-pandemic levels.”
Genetic analyses of Japanese samples are ongoing, but preliminary data appear to confirm the presence of this same strain, already known for its ability to mutate rapidly and spread easily.
The most vulnerable groups and school closures
Among those hospitalized in September, nearly half were under 14 years old, a figure indicating that schools are among the main outbreak sites. Several prefectures have opted for temporary suspension of classes and a return to precautionary measures, such as mask-wearing and limiting group activities.
In Malaysia, too, the infection curve follows a similar pattern: nearly 6,000 students affected and 97 school outbreaks recorded in a single week, indicating that the Asian region is facing an early and intense flu season.
The risks for USA and Europe
For now, the situation remains confined to Asia, but the phenomenon is being closely monitored by health authorities. Italian infectious disease specialist Matteo Bassetti noted that “the H3N2 and H1N1 strains currently circulating in Japan will likely reach other countries in the coming weeks.”
The concern is not so much about a new global emergency, but rather an earlier and broader flu season compared to historical averages. If confirmed, Japan’s early start could indeed modify vaccination and surveillance strategies.
Source: Nature
