Last year’s flu epidemic was particularly intense: estimates speak of over 16 million people bedridden by flu-like syndromes over the course of the winter, a new record since the start of monitoring by the Higher Institute of Health. And this year we risk repeating it. In fact, more and more evidence indicates that the 2025-2026 flu season could prove early and particularly troublesome. Like in Japan, where the health authorities have already declared the start of the flu epidemic much earlier than normal: it is only the second time in two decades that the virus has started circulating so early in the Asian country, and when it happens it often heralds a rather intense epidemic in the rest of the northern hemisphere too.
The epidemic in Asia
Currently, over six thousand cases of influenza have been confirmed in Japan, 287 hospitalizations caused by influenza viruses, and over 100 schools have been closed due to the high number of infections. According to Japanese standards, the influenza epidemic begins when the country’s three thousand sentinel health facilities reach the average threshold of one patient with confirmed infection per hospital. And an average of 1.4 patients per hospital has now been reached, officially marking the start of the epidemic more than a month earlier than normal.
The news coming from the rest of the region is no longer comforting: from India, to Thailand, to Singapore, many nations have reported an anomalous number of cases in recent weeks. In Malaysia, over six thousand students have already been sickened by flu viruses, and several schools have been closed due to the high number of cases.
“The arrival of the flu peak also depends a lot on local factors and without knowing precisely what is happening in Japan, it is difficult to predict what it could mean for our country,” Pierluigi Lopalco, full professor of hygiene at the University of Salento, explains to The Vermilion. “As a general rule, however, it is practically impossible to predict the moment of the peak and the intensity of an influenza epidemic until the epidemic begins, when its progress begins to be studied and the first viral isolations begin to occur. Unfortunately, we can only say how the epidemic will go when the epidemic has already started”.
H3N2
Looking at the first signs arriving from the East is therefore not sufficient to make predictions. A more reliable clue comes from the southern hemisphere, where the winter season has just ended. “Usually we look at what happened in Australia, where they have a particularly efficient surveillance system – continues Lopalco – we check what viruses are circulating there, and we use this information to update the flu vaccine. Looking at the intensity of the Australian epidemic, however, can also provide some clues as to what to expect, and this year they actually had a particularly intense epidemic”.
Not only that, because the Australian flu season was also characterized by the circulation of a particularly aggressive subtype of influenza virus, H3N2, which is often associated with intense epidemics and more serious forms of illness and began to spread more in the last part of the southern winter. Precisely in correspondence with the period in which a high number of Australian citizens travel to Japan. The virus could therefore have arrived in Asia towards the end of summer, and given the proximity in time to the beginning of autumn and the drop in temperatures, it could be responsible for the early start of the epidemic observed in recent days.
The important thing is to get vaccinated
If H3N2 were to have high circulation here too, it is likely that we are in for a particularly intense flu season. Not that knowing it in advance changes things much: the only possible prevention against the flu is vaccines, and those should be done every year by all categories for which they are recommended, regardless of the intensity of the epidemic.
“Even if we could precisely predict the week of the epidemic peak, from a public health point of view nothing would change: the vaccination campaign must be started as early as possible to give as many citizens as possible the opportunity to get vaccinated,” concludes Lopalco. “It remains the only weapon we have against the flu and unfortunately we still have unsatisfactory vaccination rates: barely half of the elderly manage to get vaccinated, the other half remain uncovered. And let’s talk about the elderly, if we go and see the adults at risk with serious pathologies who should be vaccinated, the percentages are even lower”.