Photo: Rafael De Nadai
On Monday, a World Health Organization official reported during a news briefing from the United Nations headquarters in Geneva that transmission of the coronavirus from asymptomatic carriers was “very rare” and that health officials should put more focus on following the symptomatic cases when it comes to contact tracing.
On Tuesday, that official, Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, walked back on her claim.
The WHO walked back on its claim that asymptomatic transmission is “very rare”
Van Kerkhove clarified on Tuesday that her comments were based on only two or three studies and added that it was a “misunderstanding” to say asymptomatic transmission is rare.
“I was just responding to a question, I wasn’t stating a policy of W.H.O. or anything like that,” Van Kerkhove said.
Van Kerkhove also said that the estimates of transmission from asymptomatic people come mostly from models, which could be inaccurate representations of what is actually happening.
“That’s a big open question, and that remains an open question,” Van Kerkhove said.
What did Van Kerkhove say that lead to the confusion?
On Monday, Van Kerkhove said that while asymptomatic spreading can occur, it is not the main way that the virus is spreading.
“From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual,” Van Kerkhove said. “It’s very rare.”
Van Kerkhove said that the WHO has analyzed data reports from countries that are doing very detailed contact tracing. The contact tracers follow asymptomatic cases and contacts, and they are “not finding secondary transmission onward.”
Van Kerkhove did acknowledge that some studies have found evidence of asymptomatic or presymptomatic spread in both nursing homes and household settings.
Van Kerkhove also noted that more research and data are needed to fully understand whether coronavirus can spread widely through asymptomatic carriers.
As a result of these findings, Van Kerkhove said that health officials should be most concerned with symptomatic cases in their areas, focusing policy mainly on tracking cases in which individuals show symptoms of COVID-19.
“What we really want to be focused on is following the symptomatic cases,” Van Kerkhove said on Monday. “If we actually followed all of the symptomatic cases, isolated those cases, followed the contacts and quarantined those contacts, we would drastically reduce [the spread of the virus.]”
What are other scientists saying?
Other scientists criticized the organization for creating confusion over the issue of asymptomatic transmission. The issue goes beyond what an individual deems as safe, as information from the WHO affects public policy around the world. So far governments have required or recommended face masks and social distancing measures due to the risk of asymptomatic transmission of the virus.
“All of the best evidence suggests that people without symptoms can and do readily spread SARS-CoV-2, the virus that causes Covid-19,” scientists at the Harvard Global Health Institute wrote in a memo on Tuesday.
“Communicating preliminary data about key aspects of the coronavirus without much context can have tremendous negative impact on how the public and policymakers respond to the pandemic,” the authors continued.
Additionally, a widely cited paper suggests that people are most infectious about two days before they begin to feel any symptoms, meaning they spread the virus most when they are presymptomatic.
What is the difference between asymptomatic and presymptomatic?
Asymptomatic means that the carrier of the virus does not develop any systems throughout the course of having it.
On the other hand, presymptomatic refers to the early stages of an illness, before the patient develops any symptoms. Patients who show no symptoms at first, but eventually develop some after a few days of contracting the virus, are presymptomatic. As mentioned, the CDC estimates that 40% of the of COVID-19 spread occurs before patients feel any symptoms.
On May 22, the CDC announced that it estimated that 35% of coronavirus patients are asymptomatic and that 40% of coronavirus transmission occurs before people feel sick.
Social distancing was enacted as a main tactic to slow the spread of coronavirus because it was thought that asymptomatic and presymptomatic carriers of coronavirus could very actively spread it to others.
Jennifer Fabiano is an SEO reporter at Ladders.