Where are we actually?
It simply had to do with the fact that not all figures had yet been processed due to a malfunction, but it was a record: on Monday, RIVM reported more than 100 thousand positive test results in one day for the first time. Spread out over several days, an average of almost 80 thousand people now test positive every day, so much that RIVM cannot process all the results in time. While a month ago there were ‘only’ close to 15 thousand.
And those are just the cases that end up in the official statistics. “We do not know how many people test themselves at home and do not go to the GGD,” says a spokesperson for the RIVM. “Except that there must be a lot of them.” In fact, the advice is to go to the GGD for confirmation after a positive corona test. But figures from the RIVM Behavioral Unit show that many Dutch people only do a self-test – and that roughly half of the population did not go to the test street in the event of complaints.
It can’t go on like this forever, can it?
When the peak of Mount Omikron is in sight, nobody knows. However, the increase may suddenly come to an end, says professor of theoretical epidemiology Hans Heesterbeek (Utrecht University): ‘At a certain point there are too few susceptible people. And if you increase very fast, you also go faster through the population, and you reach the point sooner that not every infected person can make a new case.’
A very tentative indication of where the peak is, countries that already seem to have gone over the top of the Omikron mountain. Denmark peaked at about 5,600 cases per 100 thousand inhabitants per week, in France the peak was at almost four thousand confirmed cases per 100 thousand inhabitants. The Netherlands has 2,700 positives per 100 thousand inhabitants: the top can never be far away.
Belgium also announced on Tuesday that it has most likely passed its peak, with more than 3,100 weekly cases per 100,000 inhabitants at its peak.
Is the peak already in sight for us?
The epidemic seems to be spreading through the population according to a fairly fixed pattern: after the twenties with their busy social lives, the virus takes root in teenagers and schoolchildren, followed by the parents (thirties and forties), followed by the elderly. In the latter group, roughly from the age of 60, the virus has not yet revived very much, whether or not as a result of the booster shot.
The peak will therefore come earlier for some age groups. Among the people in their twenties, among whom the omikron variant spread very quickly at the beginning of January, there was a cautious decline for a few weeks, but the figures are rising again this week – although a lot of elbow room is appropriate, because perhaps people have simply started testing more.
In any case, Heesterbeek understands that people are still cautious about reopening society. ‘At some point you will have to say: let it go, we’ll let it go. We’re getting close to that point.’
The peak in hospital figures may take a while, even if the number of infections falls. It usually takes one or two weeks before a lower infection rate translates into fewer new corona patients in hospital.
And then? Is the fire over then?
Most disease peaks have a strongly symmetrical shape, says Heesterbeek: the steeper up, the steeper it is down. How steep that is mainly has to do with the infectivity of the virus in question if you let it run its course (the ‘R-zero’) and the speed at which the virus causes new infections.
These are both variables, which are higher with omikron than with previous variants, resulting in a steeper peak. “You go up exponentially. The moment infections peak, the R is exactly 1. And after that you go down exponentially again.’
That shape – a sharp peak, followed by an equally sharp drop – is becoming visible in the infection figures of Denmark and France, among others. And in South Africa: first the number of infections there increased fivefold in two weeks, then the number of infections fell again by a factor of five in two weeks.
But beware, Heesterbeek warns: in practice, anything can disrupt that beautiful, smooth symmetry. Such as corona measures. In the United Kingdom, the decline stopped after Johnson canceled the measures, in Denmark the road suddenly became steeper when the country relaxed its corona policy while there were still enough susceptible people.
Another factor is the reinfections. If omikron can reinfect people several times in quick succession, the wave of disease would disappear less quickly than it came. ‘The graph then gets a thick, long tail. Certainly when the measures are released,’ says Heesterbeek.
At first sight, this seems to be the case in South Africa, where the omikrona has passed, but the virus is still simmering for a remarkably long time, at a level of about 40 reported infections per 100 thousand inhabitants per week. By the way, most people are properly protected against another infection for at least two or three months immediately after they have had the virus or have been boosted.
With the cooperation of Serena Frijters