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Heinsberg study: Around 20 percent of those infected with corona show no symptoms
According to official information, over 160,000 people in Germany have so far been infected with the novel coronavirus SARS-CoV-2. However, according to one study, the number of infected people could be close to two million. In addition, the scientific study shows that about 20 percent of those who have contracted the infection have no symptoms.
The district of Heinsberg in the Cologne region in North Rhine-Westphalia is the focal point for the corona virus. After a carnival session in mid-February there was an early and massive spread of the pathogen in Germany. As part of the so-called Heinsberg study, a research team determined, among other things, the mortality rate of the infection. This is significantly lower than assumed, as the first interim results already showed. The study results have now been presented to the public.
Important insights for the whole country
“In the Heinsberg district, there was a large number of people who were infected with the Corona virus earlier than at any other place in Germany. The district of Heinsberg is thus the first region - from here important insights for the whole of Germany can be derived, ”said North Rhine-Westphalian Prime Minister Armin Laschet in a communication on the first interim results of the so-called Heinsberg study.
The results of the study have now been published in advance and are now being presented to science and the public. A publication in a peer-reviewed journal will follow.
According to a message, a research team led by Prof. Dr. Hendrik Streeck and Prof. Gunther Hartmann from the University of Bonn surveyed, sampled and analyzed a large number of residents as part of the study in the village of Gangelt in the Heinsberg district.
Percentage of deaths among those infected
The focus of the study is the infection fatality rate (IFR), which indicates the proportion of deaths among those infected.
This must be differentiated from case fatality rate (CFR). As stated in the communication, the IFR is the more reliable parameter for various reasons, and its determination is required internationally for SARS-CoV-2.
“With our data, it is now possible for the first time to estimate very well how many people have been infected after an outbreak event,” explains study director Prof. Hendrik Streeck, director of the Institute of Virology at the University Hospital Bonn.
“In our study, that was 15 percent for the community of Gangelt. Infection mortality (IFR) can be determined from the total number of all infected people. For SARS-CoV-2, it is 0.37 percent for the outbreak in the community of Gangelt, ”said the expert.
The number of unreported cases is more than ten times the number of reported cases
With the IFR, the number of people who have died can be used to estimate how many people have contracted infection in other places with different infection rates. The comparison of this number with the number of officially reported infected leads to the so-called dark figure.
According to the information, this is about 5 times higher in Gangelt than the officially reported number of people who tested positive. If one estimates the number of almost 6,700 SARS-CoV-2-related deaths in Germany, an estimated total of around 1.8 million people would be infected.
According to the University of Bonn, this unreported figure is 10 times larger than the total number of officially reported cases (162,496 on May 3, 2020, 7:20 am).
"The results can be used to further improve model calculations on the spreading behavior of the virus - so far the data basis has been comparatively uncertain," explains co-author Prof. Gunther Hartmann, head of the Institute for Clinical Chemistry and Clinical Pharmacology at the University Hospital Bonn.
According to the researchers, the study also provides important information for further research on SARS-CoV-2, such as the risk of infection depending on age, gender and previous illnesses, the higher severity of the disease under the special conditions of a massive infection event such as in Gangelt, or the risk of infection within families.
Around every fifth infection with no noticeable symptoms
The symptom description is also an aspect of the study. The most noticeable symptom complex for this infection is the odor and taste loss previously described by Professor Streeck.
In addition, a total of 22 percent of all infected people in Gangelt showed no symptoms at all. It was noticed that people who attended the carnival session had symptoms more often.
"In order to find out whether physical proximity to other meeting participants and increased droplet formation through loud speaking and singing have contributed to a more severe course of the disease, we are planning further examinations in cooperation with specialists in hygiene," explains Prof. Hartmann.
"The fact that every fifth infection apparently has no noticeable disease symptoms suggests that it is not possible to reliably identify infected people who can secrete the virus and thus infect others on the basis of recognizable symptoms," says Prof. Martin Exner, head of the Institute for Hygiene and public health and co-author of the study.
According to the hygiene expert, this confirms the importance of the general distance and hygiene rules in the corona pandemic. “Every supposedly healthy person we encounter can unwittingly carry the virus. We have to be aware of this and act accordingly, ”says Prof. Exner.
It was also shown that the risk of infecting another person was surprisingly low in the multi-person households examined. "The infection rates in children, adults and the elderly are very similar and apparently do not depend on age," explains Prof. Streeck. There are also no significant differences between the sexes.
Test detects antibodies
A total of 600 randomly selected households in Gangelt were contacted for the study and asked to participate. From March 30 to April 6, 919 study participants from 405 households were interviewed and tested six weeks after the outbreak of the infection in Gangelt. The scientists took throat swabs and blood samples.
According to the information, in the acute phase of the infection, the PCR test, which records the “genetic thumbprint” of SARS-CoV-2, is very reliable in the first week or two. Two or three weeks after infection, the immune system forms so-called antibodies against the pathogen, which the ELISA test recognizes.
"By combining the PCR and ELISA tests, we can detect both acute and past infections," explains Hartmann. Preliminary studies have shown that the ELISA test is "wrong" in about one percent of the examinations performed and incorrectly indicates that the infection has been passed through.
"With a high percentage of infected people like Gangelt, this measurement uncertainty factor takes a back seat," says Prof. Hartmann.
In currently planned Germany-wide studies with an estimated infection rate of about one to two percent, this metrological uncertainty factor is a problem.
"Which conclusions are drawn from the study results depends on many factors that go beyond a purely scientific view," says Prof. "Society and politics are responsible for evaluating the findings and the conclusions for concrete decisions." (Ad)
Author and source information
This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
- Rheinische Friedrich-Wilhelms-Universität Bonn: Results of the “Heinsberg Study” published, (accessed: May 4, 2020), Rheinische Friedrich-Wilhelms-Universität Bonn
- Rheinische Friedrich-Wilhelms-Universität Bonn; Hendrik Streeck, Bianca Schulte, Beate M. Kümmerer, Enrico Richter, Tobias Höller, Christine Fuhrmann, Eva Bartok, Ramona Dolscheid, Moritz Berger, Lukas Wessendorf, Monika Eschbach-Bludau, Angelika Kellings, Astrid Schwaiger , Martin Coenen, Per Hoffmann, Birgit Stoffel-Wagner, Markus M. Nöthen, Anna-Maria Eis-Hübinger, MartinExner, Ricarda Maria Schmithausen, Matthias Schmid and Gunther Hartmann: Infection fatality rate of SARS-CoV-2 infection in a German community with a super-spreading event, (accessed: May 4, 2020), Rheinische Friedrich-Wilhelms-Universität Bonn
- State government of North Rhine-Westphalia: Scientific team researches the infection events of the corona virus in Heinsberg, (accessed: May 4, 2020), state government of North Rhine-Westphalia