How much coronavirus transmission comes from people with no symptoms is still a “big unknown”, a World Health Organization scientist has clarified, the BBC reports.
Dr Maria Van Kerkhove said on Monday it was “very rare” for asymptomatic people to pass the disease on.
But she has now stressed this observation was based on a relatively small set of studies.
Evidence suggests people with symptoms are most infectious, but the disease can be passed on before they develop.
Although a proportion of people test positive with no symptoms, it is not known how many of these people go on to infect others.
Dr Van Kerkhove said the evidence she had been discussing came from countries that had carried out “detailed contact tracing”,
Looking at investigations of clusters of infections from various countries, she said that where an asymptomatic case had been followed up it was “very rare” to find secondary infections among their contacts.
But she it was still a “big open question” as to whether the same was true globally.