[ad_1]
Infected people who are tested once they have no symptoms may develop symptoms later. In a study from the University of Bern, 80 percent of cases turned out to be only presymptomatic.
Only a minority of those infected with Covid-19 remain symptom-free for the entire duration of the disease, as a study from the Bern survey shows.
Photo: Roberto Pfeil (Keystone)
In a large overall study, researchers from the University of Bern determined the proportion of people infected with Covid 19 who did not develop the disease. It is, therefore, about twenty percent, as reported in the specialized journal “PLOS Medicine.”
If the number of people without symptoms were high, the so-called herd immunity should be achieved soon, according to one thesis. But: “This is most likely not the case,” epidemiologist and latest study author Nicola Low, of the University of Bern told Keystone-SDA.
So far, experts have disagreed on the extent of the infected without symptoms. Because the devil is in the details: anyone infected with a single test without symptoms can develop symptoms later; we speak of presymptomatic patients.
Children tend to remain symptom free
Low’s team has now evaluated 79 studies that examined infected people for symptoms over a long period between March and June. Consequently, out of 6,616 people, only 1,287 remained asymptomatic for the entire duration of the disease. In about 80 percent, however, symptoms appeared sooner or later.
In a narrower selection of studies in which subjects were randomly selected, not just hospital patients, the number of asymptomatic infected people stabilized at 30 percent. The researchers also found that the disease manifests itself less frequently in children than in adults.
The problem of presymptomatic patients
The overall study confirms that asymptomatically infected people play a relatively small role in the spread of the virus. The problem is presymptomatic patients who are not yet aware of their infection, Low said.
Therefore, to stop the pandemic, it is of the utmost importance to constantly adhere to general measures, such as wearing a mask and keeping your distance.
New insights into symptoms
Low and his team will keep an eye on the studies on the course of asymptomatic diseases; Since the completion of his review article, another 900 studies have been published that, according to the epidemiologist, could be relevant.
It is now known that the spectrum of symptoms is broader than initially assumed: in addition to coughing and shortness of breath, there was also loss of taste and smell, as well as pain in the extremities. With these new findings, the number of asymptomatic disease courses can be more precisely determined in the future.
http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003346
