Is there a second wave?


Prime Minister Mark Rutte (VVD) and Minister Hugo de Jonge (Public Health, CDA) will return from vacation on Thursday for a press conference on the corona virus. In Rotterdam, the number of new infections has doubled for four weeks in a row and the number of hospital admissions is also growing again. The cabinet is even considering new, regional measures in the most violent corona fires such as Rotterdam and Amsterdam. It raises the question: are we back to square one in the corona crisis?

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Last week, between 400 and 500 new cases were found per day – comparable to mid-March. That was the week in which the majority of the Netherlands went to work from home, the catering industry and schools were closed and Mark Rutte spoke to the country on TV from the tower. In short, we were at the beginning of the ‘intelligent lockdown’, the measures of which were scaled down step by step two and a half months later.

Yet the situation today is completely different. In that crucial week in mid-March, more than 100 corona patients were hospitalized every day – now there are between five and ten. And the number of infectious people in the Netherlands is now probably much lower. RIVM calculates how many people are contagious based on the number of hospital admissions and positive tests.

It’s a rough calculation, but in March there must have been around 200,000 contagious people. There are now estimated to be between 8,500 and 25,000. The “upward trend” in recent weeks is no more than “a ripple” compared to the numbers in the spring, says Louis Kroes, professor of clinical virology at LUMC in Leiden. “The numbers are rising, there is nothing to dispute. But we are now putting the numbers under a magnifying glass. ”

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Summer over

The big difference between this spring and now is that much, much more is being tested. Where in March only people with serious complaints who ended up in the hospital were tested, since 1 June anyone with complaints, even if they are mild, can pass a corona test. More than 100,000 people have been doing this every week recently. In March there were about 14,000 a week.

“We have never tested so much,” e-mails professor of virology Marion Koopmans from the Erasmus Medical Center from her holiday address. “If we had followed flu pandemics so intensively, we might have found something similar in the summer.” Koopmans points to the severe flu pandemic of 2009, when there were also infections here and there due to ‘summer parties’.

The fact that testing is so intensive makes it difficult to properly interpret the figures, confirms Kroes. “We are now on the heels of the virus, with a normal flu we only have the ‘sentinel stations’ at GPs. As a result, we don’t really know how influenza is ‘over-summering’. It is there in the winter, in the spring it decreases, in the summer we hardly find it anymore and then it is suddenly back in the autumn. Influenza may survive here at a low level in the summer, a little lower than we see now with the corona virus. ”

In short, we do not know what viruses that resemble the coronavirus do in summer, Kroes says, and that is why we do not know how ‘normal’ the upward trend of recent weeks has been.

‘Clusters in particular’

Anyway, the current upswing is not yet the second wave, both Koopmans and Kroes believe. There is no fixed definition of a ‘second wave’, but Koopmans will only speak of this if other figures also rise. Koopmans points to the Nivel network, a sample of GPs who report on viruses such as influenza and SARS-CoV-2. “We look at those sentinel stations for influenza outbreaks. We do not see an increase there yet. This also fits in with the image that it mainly concerns clusters, which can be extinguished with targeted actions. ”

The number of hospital admissions is also increasing. Last week there were more than forty a week, compared to about twenty a week earlier. But there is not yet a ‘stable trend’, says Koopmans. “I would say: if those registrations show an increase a few weeks in a row, you are talking about a second wave.”

Kroes focuses on healthcare. “The policy is aimed at ensuring that care does not overflow. Only when we get a similar situation as in March and April of this year, where healthcare cannot cope, will there be a second wave in my opinion. ”

That is not to say that the increasing number of corona cases is not a problem. Koopmans is certainly concerned. “Everything now stands or falls with the behavior of all of us,” she says.

Kroes also considers the ‘sometimes quite large sources of infection’ a risk. The picture of the epidemic is still “quite good” because the sources of infection can be identified by means of source and contact research. “It is now mainly young people who are infected. They often fall ill less often, but they too come into contact with vulnerable groups. And some of the youngsters will also become seriously ill, you shouldn’t take that too lightly. ”

With the cooperation of Rik Wassens


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