Coronavirus transmission from asymptomatic patients rare: WHO

Potential for presymptomatic transmission underscores the importance of social distancing, says WHO expert

The World Health Organization (WHO) has said that transmission of the novel coronavirus from asymptomatic patients is rare.

The head of WHO’s emerging diseases and zoonosis unit, Dr Maria Van Kerkhove, said during a press briefing: “From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual”.

She added that governments should focus on tracing and isolating people who are infected with Covid-19 and anyone who have been on contact with them.

“We have a number of reports from countries that are doing very detailed contact tracing,” she said. “They’re following asymptomatic cases. They’re following contacts. And they’re not finding secondary transmission onward. It’s very rare.”

“Some studies have indicated asymptomatic or presymptomatic spread in nursing homes and in household settings,” she said adding that more data and research is needed to “truly answer” whether coronavirus can transfer though asymptomatic carries.

Dr Isaac Bogoch and Dr Allan Detsky of the University of Toronto pointed out that the issue might of semantics and misuse of the term "asymptomatic" when referring to "presymptomatic" patients.

Asymptomatic patients never show sign of contracting coronavirus whereas presymptomatic people exhibit no signs of contracting the deadly disease for the first few days before exhibiting and experiencing the classic symptoms.

"The potential for presymptomatic transmission underscores the importance of social distancing, including the avoidance of congregate settings, to reduce Covid-19 spread," Kerkhove said.

Kerkhove added that seemingly asymptomatic carriers just did not recognise the signs of the virus."When we actually go back and say, 'How many of them were truly asymptomatic?' we find out that many have really mild disease, very mild disease."

"Comprehensive studies on transmission from asymptomatic individuals are difficult to conduct, but the available evidence from contact tracing reported by Member States suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms," she added.

In April, The Centers for Disease Control and Prevention (CDC) cited the importance of social distancing and taking precautionary measures like wearing masks in public as studies suggested that asymptomatic or presymptomatic people are able to spread the disease.

Understanding the characteristics and spread of Covid-19 has been an ongoing challenge throughout the pandemic. It is characterised by the questions surrounding the spread of the virus before patients start exhibiting symptoms.