U.S. residents are being warned of the possibility of one of the toughest flu seasons in history coming to its shores.

Right now Europe, specifically England, is facing one of the toughest ever winters in its history with an early wave of flu cases being reported.

“Flu rates have started climbing much sooner than usual this year, driven largely by cases in young adults and schoolchildren,” according to a report from the British Medical Journal [bmj]. 

  And experts warn that the H3N2 strain, currently the dominant strain in flu cases in England, mutated seven times over the summer, making it more severe than normal, according to the bmj. 

There are growing concerns that hospitals will be overwhelmed this winter. Health officials have urged all eligible groups, including people over 65, people with certain longterm conditions, pregnant women, and children, get vaccinated, according to bmj. 

According to a report from bmj, the dominant H3N2 strain of influenza mutated multiple times over the summer making it more severe. 

Flu cases in Japan have seen an early surge as well leading health authorities to declare an influenza epidemic in October. 

According to Scientific America, as of Oct. 10 there were 6,013 cases of influenza reported in Japan, more than 100 schools closed and nearly half of the 287 people who were hospitalized for flu in September were children 14 years old and younger. 

According to the Centers for Disease Control and Prevention (CDC), the flu activity in the U.S. has remained low but cases are increasing especially among children. 

The flu mutation is called “subclade K” and it appears to be the predominant strain globally. 

“Because influenza viruses don’t need a passport, I think it’s only a matter of time before this strain shows up in the United States,” said William Schaffner, MD, an infectious disease specialist and a professor of preventive medicine and health policy at the Vanderbilt University School of Medicine in Nashville, Tennessee. “It may even be here now, but because of the government’s recent shutdown, we haven’t heard much information about flu now for weeks from the CDC.”

According to a report from the CDC released in September, “During the 2025 Southern Hemisphere influenza season, seasonal influenza vaccination reduced influenza-association outpatient visits by 50.4% and hospitalization by 49.7%. [Therefore] CDC recommends that all eligible persons aged [greater than] six months receive the seasonal influenza vaccine.”