Coronavirus: SARS-CoV-2 transmission possible before symptoms start

Coronavirus: SARS-CoV-2 transmission possible before symptoms start

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SARS-CoV-2 contagion exists before the onset of symptoms

The SARS-COV-2 coronavirus can be transmitted before the first symptoms appear. This was shown by a German research team in a recent study.

Are people infected with the corona virus contagious before they even notice anything? This could make it more difficult to contain the pandemic. A German study has now investigated the question. The study, published in The Lancet Infectious Diseases, confirmed that infected people can be contagious before the first symptoms appear.

The first Corona cases in Germany were analyzed in detail

Four months after the first corona cases in Germany, scientists analyzed the contagion chains of the first group of patients in detail. The researchers led by Merle Böhmer from the Bavarian State Office for Health and Food Safety, Udo Buchholz from the Robert Koch Institute and Victor Corman from the Berlin Charité examined the first Corona cases in Germany that were related to the car supplier Webasto near Munich. A Chinese colleague had introduced the pathogen during a business trip.

Infectivity before the onset of symptoms

In at least one of the 16 cases examined, an infected person passed on the coronavirus before he had symptoms, the authors report. This may even have been the case for five other cases. In at least four cases, an infected infected other people on the day the symptoms started. The authors write five more cases during this period.

A huge challenge

The team concluded that infectivity was significant before the onset of symptoms or shortly thereafter, was a huge challenge for health measures. In addition, the incubation period, which averaged 4.0 days, was often very short. "Global containment of Covid-19 could be difficult to achieve," the researchers emphasize.

This is also underlined by Jan Rybniker and Gerd Fätkenheuer from Cologne University Hospital in a “Lancet” comment. “This matches other results that estimate the frequency of presymptomatic transmission to up to half of all infections. This is one of the most serious obstacles to controlling the pandemic. "

Difficulty tracking contacts

In the event of a larger spread, the traditional tracking of contacts is no longer sufficient. "Therefore, new technologies such as contact tracking apps are urgently needed to effectively control the pandemic," emphasize the Cologne experts.

Annelies Wilder-Smith from the London School of Hygiene & Tropical Medicine (LSHTM) also emphasizes this in a statement: The study underlines the importance of tracking transmission chains through contact tracing and quarantine of contacts. “All countries that have rigorously followed up on contacts have been most effective in keeping the number of new infections small. South Korea, Taiwan, Hong Kong, Thailand, Vietnam, and Singapore are clear examples of countries that do not save on resources and technology to rigorously identify contacts. Everyone was successful. ”(Vb; source dpa)

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.

Graduate editor (FH) Volker Blasek


  • Merle M Böhmer, Udo Buchholz, Victor M Corman, and others: Investigation of a COVID-19 outbreak in Germany resulting from a single travel-associated primary case: a case series; in: The Lancet Infectious Diseases, 2020,

Video: Tracking disease progression of COVID-19 (October 2022).