One in five people infected with the novel coronavirus has no symptoms, according to a new study published on Monday.
A team of researchers from the University of Bonn has conducted an in-depth study of the sick identified in Gangelt, a municipality with about 11,000 inhabitants in the district of Heinsberg, western Germany.
The region is one of the most infected per capita in Germany following the spread of Covid-19 by an infected couple during carnival celebrations on 15 February.
The study which is based on interviews and analysis of 919 people from 405 households, draws conclusions on the fatality rate of the infection. In Gangelt, some 15% of the population have been infected. The death rate among these patients has reached 0.37%.
Two or three weeks after the infection takes place, the immune system builds antibody responses against the virus, the study notes.
Notably, asymptomatic infected individuals in the study present with substantial antibody concentrations.
However a lack of virus neutralization does also not exclude a past infection as there is ample evidence that not all antibody responses neutralize, but may still provide some degree of protective immunity.
“If we extrapolate this figure to the nearly 6,700 deaths associated with Covid-19 in Germany, the total number of people infected would be estimated at around 1.8 million,” according to the authors of the study, which is a number “ten times greater than the total official number of reported cases.”
“In Gangelt, 22% of the people infected showed no symptoms,” the study also reveals. “The fact that apparently one in five infections occurs without noticeable symptoms suggests that infected persons who secrete virus and can infect others cannot be reliably identified on the basis of recognizable symptoms of the disease,” Professor Martin Exner, co-author of the study, notes.
The study also reveals that infections within the same family are fairly low and that more generally, the infection rate appears “very similar in children, adults and the elderly and apparently does not correlate to a certain age or gender.”