A detailed study involving 303 people in South Korea shows that 29% of people infected with the coronavirus have never developed symptoms, but they carry within them as much virus as symptomatic persons.
The study, led by Seungjae Lee, University of Soonchunhyang and published Thursday in the american journal Jama Internal Medicine, focused on an outbreak of infections in a religious group in south Korean Daegu, in February. The authorities had decided to place the isolation of the positive cases with little or no symptoms, in a building of the dormitories of the government where the doctors and nurses have carefully monitored the evolution of their symptoms and tested their viral loads regularly.
The group was young, an average age of 25.
Out of 303 people, 89 have never developed symptoms, a proportion of 29%.
Since people were locked away until they get negative tests, the medical staff was able to distinguish the cases in presymptomatic real asymptomatic. In fact, 21 people were initially positive for the coronavirus without symptoms, but ino fine had symptoms. Many studies, in testing patients that once may confuse case presymptomatic and asymptomatic cases.
The main teaching is that the concentrations of virus in the asymptomatic were “similar to those of symptomatic patients,” report the authors.
But finding the viral particles residual in the nose, throat or lungs does not necessarily mean that these people were infectious. This is one of the major issues of the pandemic: how many asymptomatic cases are they vectors of the virus? On the one hand, they do cough not, but on the other hand, they do not put in solitary confinement and are thus in contact with other people.
“It is important to note that detection of viral RNA is not synonymous with the presence of an infectious virus and transmissible”, warn the authors of the study. Large epidemiological studies and experimental work are needed to understand it.