NUcheckt checks claims for reliability. This time we look at the claim that the GGD test cannot show whether you can infect others with the coronavirus. That statement is correct, but if you are tested when you just have complaints and the result is positive, then it seems likely that you are contagious.
The number of people who test positive for the coronavirus is increasing again. In response, our reader platform NUjij suggests that many of the people who test positive now are no longer contagious and have become infected long ago.
The claim is substantiated on NUjij by pointing out that the test using the GGD cannot measure whether the virus is still intact and therefore contagious. How does this work?
“Furthermore, it says nothing about the infectiousness of this person, nor whether he is or will be sick.”
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Which test does the GGD use?
The GGD uses a so-called PCR test. With this test, the GGD determines whether you are currently infected with the coronavirus. The result is positive if genetic material of the coronavirus has been found in your throat or nose.
What does a PCR test show?
Jeroen van Kampen, clinical virologist at Erasmus MC, explains to NU.nl that PCR tests are very good at detecting an infection. “If the result is positive, you are infected with the coronavirus. But with a PCR test you can indeed not show whether an infected person can still spread the virus.”
This is possible in the lab, with a so-called virus culture. “You then mix samples from the throat and nose in the lab with cells in which virus particles can multiply. If the cells in the lab become infected, there is still infectious virus in the nose and throat. However, a virus culture is a rather complicated and time consuming test and therefore probably not suitable to be performed on every COVID-19 patient. “
When is someone no longer contagious?
People who are not contagious can still test positive if they have recently been infected with the corona virus. German research among corona patients with mild complaints showed that the majority of throat samples contained infectious virus in the first week of the patients studied experiencing complaints. No infectious virus was found after the eighth day, but some patients still tested positive with the PCR test.
Van Kampen discovered in Erasmus MC that it can take up to fifteen days in seriously ill COVID-19 patients until they are no longer contagious and it can take much longer before a PCR test comes back negative. “Some patients still had a positive PCR test forty days after the first complaints.”
Van Kampen explains that for these admitted patients, two tests have now been developed that are less laborious than a virus culture. “Nursing in isolation is psychologically hard on the patient and relatively expensive. So you don’t want to do this for longer than necessary. In people who have been admitted to COVID-19 a long time ago and who we suspect are no longer contagious, Erasmus MC has now applied these two tests to see if someone can go out of isolation. “
“It is not clear whether these tests are also reliable in patients who only have mild complaints,” says Van Kampen.
What does this mean for the corona figures?
Do people who were infected weeks ago and are therefore no longer contagious now test positive for the coronavirus?
The Dutch are advised to have themselves tested if they have complaints that match the corona virus. If you test people with complaints, according to virologist Marc Van Ranst, there is a good chance that you will discover a recent infection and someone is therefore still contagious, he explained. VRT NWS. “If you test people who have no symptoms at all because of contact research, you may find an old infection,” says the Belgian equivalent of Jaap van Dissel of the RIVM.
So it is possible that some people who test positive now had an infection a few weeks ago and are no longer contagious. However, the probability of this seems small, since the Netherlands is calling for you to be tested when you just have complaints.
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