According to the European Centre for Disease Prevention and Control, 5,293 cases of flu have been registered in Croatia since the beginning of the 2021/2022 flu season, which means that in the past two years this seasonal infection has almost completely receded, writes Jutarnji List.

In the 2019/2020 season, in the time before the Covid-19, almost 60,000 cases of influenza and about thirty deaths were recorded in Croatia.

Some of the world's scientists suggest that this trend could continue, that is, that the flu, as a real seasonal disease, may not return for years to come, due to the so-called cross-immunity to viral infections or, as it is professionally called, viral interference.

"This means that infection with one virus can trigger immunity that protects against a number of other viral diseases, but we still don't have real evidence of this when it comes to Covid-19," explained Professor Ellen Foxman, an immunologist at Yale University.

Namely, experts expected that the so-called “twindemia”, i.e. that Covid-19 and the flu would attack at the same time and that hospitals would be overcrowded.

But, fortunately, that did not happen, so the number of people infected with Covid-19 was at a record high, but the flu remained at low levels. The wearing of facemasks, scientists believe, also contributed to the low levels of flu cases. And they say that it is not clear how long the so-called cross-immunity will last, but it is possible that a single virus infection can trigger parts of the immune system that can then fight a number of other viruses.

For example, high levels of protein allow the production of interferon in infected cells, or part of the immune system that protects us from the virus. Given that many were infected or vaccinated during the pandemic, natural immunity was achieved, regardless of whether it was an infection or a vaccine, experts say.