Silke Buda, leader of the Influenza Working Group at the government disease control centre, said that large numbers of people had fallen ill with the disease this year.

“This is one of the most serious flu outbreaks of recent years,” she said.

So far 40,000 people have been treated for the flu this season, with especially large numbers of people aged 39 to 59 affected.

Vaccinations less effective

The constantly-evolving flu virus is a tough target to pin down for developers of vaccinations.

The type of virus prevalent this year means that even vaccinated patients are not as well protected as during previous outbreaks.

“Despite all our efforts, it's difficult to predict so far in advance the exact subtype of influenza that the vaccination has to counteract,” said Carlos Guzman of Brunswick's Helmholtz Centre for Infectious Disease Research.

Outbreaks of the same strain in the winters of 2012-13 and 2008-09 saw up to 20,000 people die from the infection, although Buda said it was too early to estimate what the toll might be this year.

Most at risk are older people who are already ill.

“The weaker the immune system, the more difficult it is to react properly to a new influenza virus,” Buda said.

Both experts emphasized that it is still important to have flu jabs in autumn, as they offer the best possible protection against a possible infection.

Currently only around 30 percent of people in Germany get themselves vaccinated, far short of the World Health Organization (WHO) recommendation that at least 75 percent of older people be immunized.