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Breaking the chains of infection: this is the most important measure in the fight against the pandemic. Above all, it is essential that there are as few contacts as possible in which the Sars-CoV-2 virus can be transmitted from an infected person to another who has not yet been infected. A new meta-study from Britain now suggests that infected people may have to stay home longer than before, and the spread of the virus could still be prevented.
In the debate, however, it is first important to distinguish between two terms: quarantine and isolation.
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quarantine means the separation of contact persons who do not have symptoms and have been shown to be infected. It can be voluntary or ordered by the authorities. The quarantine period in Germany will be shortened from 14 to 10 days on December 1, on the condition that a corona negative test is available at the end of this period, regardless of whether it is a PCR or rapid antigen test. . “Ten days of quarantine with a quick test at the end is as safe as 14 days of quarantine without a test,” said Federal Health Minister Jens Spahn. “But it means four days less restrictions for those affected.”
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Since Isolation It is spoken against, if it is found that infected people are not allowed to leave their apartment so as not to infect anyone. The period for this has been ten days so far, at least if the patient has been asymptomatic for 48 hours at the end of this time and, if the evolution is severe, he or she can also present a negative PCR test.
The duration of quarantine or isolation depends on the answer to a crucial question: how long does an infected person shed such large amounts of virus that they can infect other people? From an epidemiological point of view, when in doubt, it makes sense to choose the longest period possible. However, there is a risk that people will not follow the rules. Anyone who goes outside again before the deadline can be a danger to others. Ultimately, official rules can, at best, be selectively checked.
In Germany, late in the summer, there was a lively discussion about reducing quarantine and isolation times. This shortening has now also been decided on quarantine. From their point of view, the new meta-evaluation by the British researchers now suggests talking again about the duration of isolation. Mücke Çevik’s team from the University of St Andrews reports in the trade journal “The Lancet Microbe” on the findings on when and for how long infected people shed the Sars-CoV-2 virus.
Short transmission window
The researchers analyzed 79 studies on Sars-CoV-2 and another 19 studies on related pathogens. “In none of the studies was a live virus detected after the ninth day of illness despite a persistently high viral load,” they concluded. Viral loads in the upper respiratory tract appear to peak in the first week of illness. Infected people without symptoms also appear to have about the same amount of virus as patients with symptoms. In asymptomatic people, however, the virus apparently clears the body more quickly.
“This meta-analysis shows how short the transmission window is,” says virologist Michael Mina of Harvard University, who was not involved in the study. Even those who do the PCR test as soon as possible have already secreted 90 percent of the viruses when they get the result.
People with Covid-19 are typically most infectious a day or two before symptoms appear, according to the study, and up to about five days after they begin. However, in some cases, patients can carry genetic fragments of the pathogen in the nasopharynx for up to three months.
RKI experts consider shortening essential
In the case of those who are actually infected, it is better to limit the incubation period and infectivity than for contact persons. Therefore, here too a shortening of the isolation period can be discussed with better facts. A period of just five days could cause more infected people to adhere to isolation, so Çevik. Their reasoning is likely based on an August opinion poll, according to which only 20 percent of respondents in Britain actually follow the rules of self-isolation. The reasons for this may be financial in nature or the feeling that you are no longer ill.
At the end of September, a research group from the Robert Koch Institute presented an opinion on the duration of the quarantine and isolation of Covid-19. “Shorten the isolation period to less than 10 days […] they go hand in hand with a correspondingly large increase in risk, ”he says.
