Side effect of the corona measures: Will the flu wave fall flat this time?

By Klaus Wedekind

The flu season usually starts in autumn. But a look back into spring and the experiences of the past few months in the southern hemisphere show that it could be canceled this year thanks to the Corona measures.

Seasonal flu is not considered to be as dangerous as Covid-19, but this disease also kills many thousands worldwide every year. In the autumn and winter of 2017/18, Germany was hit particularly hard, with the RKI recording almost 1,700 deaths in Germany. According to the institute, however, influenza is often not entered on the death certificate as the cause of death; it estimates the actual number of victims at 25,100.

Last season was just as “normal” as the previous one with around 950 confirmed flu deaths, but it ended abruptly at least two weeks earlier than usual. And it could even fail completely in the coming cold months. This is due to the corona measures, which have also proven to be extremely effective against other respiratory diseases.

In its preliminary analysis of the past flu wave, the RKI comes to the conclusion that it started in the second calendar week of 2020 and ended in the twelfth mid-March. With a duration of 11 weeks, it was significantly shorter than in the previous five seasons, in which the flu epidemic lasted 13 to 15 weeks. A distinction has to be made between the flu season, which usually lasts from the beginning of October to mid-May, and an influenza wave in which influenza cases increase.

The RKI considers it very likely that the Corona measures, which began on March 9 with the cancellation of major events in the eleventh calendar week, “contributed significantly” to this. Institute boss Lothar Wieler even said on an MDR talk show: “We ended the flu through the measures.” A look at the other half of the globe to Argentina, Australia or South Africa confirms this thesis. Because winter is over there and a flu wave should just run out. But there was none at all.

Southern hemisphere had “flu free”

As the WHO FluNet charts show, a flu wave began to build up in some countries in March, but it flattened out again at the end of the month. In other states, next to nothing has happened. The consequences are dramatic. On August 17, reported that there had not been a single influenza death in Australia since May.

The example of South Africa shows how abruptly the beginning flu wave collapsed in the southern hemisphere.

(Foto: WHO)

It looks similar in New Zealand. “It’s amazing, there’s just nothing. No influenza,” The Guardian quoted Michael Baker, professor of health at the University of Otago in Wellington, saying. His South African colleague Cheryl Cohen of the National Institute of Communicable Diseases (NICD) told “CBS News” a few days ago that what happened was completely unprecedented. “We saw that we just didn’t have a flu season in South Africa this year.” And the WHO also came to the conclusion in its influenza update of September 14: “The flu season has not started in the southern hemisphere.”

How many lives the Corona measures saved by suppressing the flu wave can be estimated from the average number of deaths per 100,000 inhabitants in the previous five flu seasons. “The Economist” has compiled them for a number of countries in the southern hemisphere. In Argentina there were around 16, in Chile 12 and in South Africa even 25 people per 100,000. New Zealand, Australia and Paraguay got off lightly with rates between 0.5 and 6.5 deaths. However, in these countries as well, as in Germany, the actual numbers are probably much higher.

Open schools are a problem


Open schools could make the difference compared to spring.

(Foto: picture alliance/dpa)

The experiences from spring and those of the past few months in the southern hemisphere suggest that the effect is now repeated in the northern hemisphere. “You will have a flu season,” says Michael Baker, “but I expect it to be a lot less severe.”

However, the current situation in Germany is not entirely comparable to March and April; above all, the measures are no longer so strict. The schools that are open could make a big difference. Because the RKI wrote in April: “Since children play an essential role in the spread of the annual flu, the school closings from the twelfth calendar week in 2020 are particularly worth mentioning here.”

It could also turn out differently

Virologist Christian Drosten therefore understands that there are considerations to vaccinate children against the flu. Here, too, the main thing is to protect the elderly, he said on the weekend in the “Handover” podcast. The measures had strongly pushed back all viruses transmitted through the air and in the southern hemisphere the influenza had in principle failed. But whether the flu wave will fail this time is not certain. “That is of course a speculation that nobody wants to answer for if it doesn’t turn out that way in the end.”

If the flu wave falls flat this time, it could also be detrimental for years to come. Because because practically no one is infected, immunities do not develop. It is therefore theoretically possible that influenza viruses or other diseases will spread faster in the future if there are no longer any corona measures. This is understandable, but there is no data on it, “because something like this has never happened before,” says Drosten. “From a feeling, I would say that I don’t expect very strong effects, but who knows.”


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