Maria Van Kerkhove, the World Health Organization’s (WHO) technical lead for coronavirus response earlier mentioned that the spread of COVID-19 by someone who is not showing symptoms appears to be “very rare”. However, Van Kerkhove clarified her remarks, citing a “misunderstanding”.
“I was referring to very few studies, some two or three… I used the phrase ‘very rare’, and I think that is a misunderstanding to state that asymptomatic transmission globally is very rare. What I was referring to was the subset of studies,” she stated during a discussion re-broadcast on the WHO’s Twitter account.
What Van Kerkhove stated before
Previously, Van Kerkhove in a media briefing said that the spread of COVID-19 by someone who is not showing symptoms appears to be rare. She also said that it comes from data that they have.
“We have a number of reports from countries who are doing very detailed contact tracing. They’re following asymptomatic cases, they’re following contacts and they’re not finding secondary transmission onward. It is very rare—and much of that is not published in the literature. We are constantly looking at this data and we’re trying to get more information from countries to truly answer this question. It still appears to be rare that an asymptomatic individual actually transmits onward,” she said during that media briefing.
Her remarks caused plenty of social media coverage, and sparked a reaction from part of the scientific community. Liam Smeeth, a clinical epidemiology professor at the London School of Hygiene and Tropical Medicine, said he was “quite surprised”.
“There remains scientific uncertainty, but asymptomatic infection could be around 30 per cent to 50 per cent of cases. The best scientific studies to date suggest that up to half of cases became infected from asymptomatic or pre-symptomatic people,” he said.
During WHO’s discussion re-broadcast where Van Kerkhove clarified the misunderstanding, WHO Tweeted that they are “still learning about the disease every day”, and that they “need more data to better understand transmission”. You can watch the re-broadcast here.
We also reported earlier on 1st June that our Health Director-General Datuk Dr Noor Hisham Abdullah also said asymptomatic COVID-19 positive individuals do not have the potential to infect others. This is because they have a low “virus load” compared to those who are symptomatic. However, he said that infectivity could occur two days before the individual showed symptoms.
And like many scientists that spoke out when Van Kerkhove made her earlier statement, it is not scientifically possible yet to affirm that asymptomatic carriers of the virus are not infectious.