Early indicators in Europe suggest the upcoming flu season could be a severe one for the elderly, Europe's public health agency said on Tuesday.
Flu circulation is already above the seasonal threshold in Croatia, the agency said, which is unusually early.
The main reported type of flu virus circulating is one that disproportionately affects older people, the European Centre for Disease Prevention and Control (ECDC) said in a statement.
Vaccines often are less effective against it, the agency warned. Many European governments are beginning vaccine campaigns to encourage vulnerable populations to receive the flu jab.
"The early detections of the A (H3N2) subtype are an indication that the upcoming flu season could be severe, although we cannot know for sure what the upcoming flu season will look like," said Pasi Penttinen, head of ECDC’s influenza programme.
"A steep rise in flu infections during the ongoing COVID-19 pandemic could have serious consequences for the elderly and those with weak immune systems and could place an additional burden on health systems already strained by COVID-19."
Last winter, as governments imposed restrictions as COVID-19 circulated widely among unvaccinated populations and sent large numbers of people to hospital, flu decreased significantly. But as people gather in larger numbers without pandemic restrictions, winter viruses are expected to increase.
Approximately 20% of the population get the flu each year, the ECDC said. One in four infected people develop symptoms.
The elderly and people who are pregnant or who have chronic health issues are at greater risk of experiencing severe complications from the flu.
The agency estimates that tens of thousands of people die of flu complications each year in the European Union. Hundreds of thousands of people are hospitalised for flu.