KUALA LUMPUR, June 10 — The actual rate of asymptomatic transmission of the coronavirus is still unknown as scientists have yet to determine the incidence of carriers who don’t show symptoms infecting others, a World Health Organization (WHO) official clarified.
The clarification came after Dr Maria Van Kerkhove, head of WHO’s emerging disease and zoonosis unit, said asymptomatic Covid-19 transmission was “very rare”, prompting strong feedback from public health experts, suggesting that the agency had blundered or miscommunicated, as reported by STAT.
Dr Kerkhove reportedly backtracked on her previous comments and said that the definite rates of asymptomatic transmission are still unknown.
“The majority of transmission that we know about is that people who have symptoms transmit the virus to other people through infectious droplets, but there are a subset of people who don’t develop symptoms, and to truly understand how many people don’t have symptoms, we don’t actually have that answer yet,” Dr Kerkhove reportedly said.
Some of the confusion arose from the definition of “asymptomatic infection”, and the different ways that the term is used, as cited by STAT.
It was reported that the term is sometimes also used to describe people who have yet to show symptoms of the coronavirus, during which they are pre-symptomatic, a period when the infected person becomes infectious before feeling ill.
“The WHO created confusion yesterday when it reported that asymptomatic patients rarely spread the disease,” an email from the Harvard Global Health Institute reportedly said Tuesday.
“All of the best evidence suggests that people without symptoms can and do readily spread SARS-CoV-2, the virus that causes Covid-19. In fact, some evidence suggests that people may be most infectious in the days before they become symptomatic — that is, in the presymptomatic phase when they feel well, have no symptoms, but may be shedding substantial amounts of virus.”
Dr Kerkhove yesterday also admitted that her use of the phrase “very rare” had created miscommunication, and explained that she had based that phrasing on findings from a small number of studies that followed asymptomatic cases and tracked the number of their contacts that became infected from them.
She further added that she did not mean to indicate that “asymptomatic transmission globally” was rarely happening, as that claim has not yet been proven.