Μake us preferred on Google A new genetic variant of the influenza virus, an unusually early start to the flu season in Greece and sharp week-to-week changes in infection rates are shaping an unpredictable start to this year’s flu season.
In the United States, flu activity is rising earlier than expected, with scientists closely monitoring a genetic change known as G155E. Although available data do not currently indicate that it causes more severe illness, experts warn that influenza can spread across borders and stress the importance of timely vaccination.
Most flu samples tested in the U.S. so far have been positive for the familiar H1N1 subtype. However, the early onset of flu activity on the West Coast has drawn attention to G155E, a genetic change in hemagglutinin, a protein on the surface of the virus that plays a key role in how the immune system recognizes it.
According to Reuters, scientists say people who have previously encountered H1N1 through infection or vaccination may have only partial protection against this altered version of the virus. Younger people are a particular concern because some may have less previous immune exposure to H1N1 strains with similar genetic changes.
Dr. Jennifer Duchon, a pediatric infectious disease specialist at Mount Sinai Children’s Hospital in New York City, told Reuters that there are concerns about the possibility of more severe illness among this group.
Greece sees an earlier start to flu season
The situation in Europe is different. According to the latest data from the European Centre for Disease Prevention and Control (ECDC), influenza activity across the continent remains low for this time of year.
Greece, however, appears to have entered its flu season about 15 days earlier than usual, raising questions about how infections will develop in the coming weeks.
“The next three weeks will be critical,” said Theodora Psaltopoulou, a professor of therapeutics, epidemiology and preventive medicine at the National and Kapodistrian University of Athens’ medical school.
The period will help determine whether the early increase in flu activity in Greece subsides or is followed by another rise, she said.
Recent surveillance data have shown fluctuating trends. During the week of October 5-11, the proportion of positive flu tests in the community exceeded 10%, reaching the epidemic threshold used to signal seasonal influenza activity. The rate then declined in the following report.
Hospital admissions, however, moved in the opposite direction, rising from 27 to 52. The increase illustrates why a decline in one indicator does not necessarily mean that the overall situation is improving.
Experts urge people not to delay vaccination
Weather conditions and crowded indoor settings can influence how easily the virus spreads, Psaltopoulou said. She cautioned against drawing firm conclusions about the season’s trajectory from a single week of surveillance data.
Her advice is to get vaccinated without unnecessary delay, particularly for people at higher risk of complications from influenza.
People do not need to wait until mid-November to receive their flu shots, she said.
The international target for influenza vaccination coverage among people aged 65 and older is at least 75%. Yet the latest comparative ECDC figures, covering the 2024-2025 season, show that vaccination coverage among older adults across the European Union and European Economic Area stood at just 47%.
