We Might Be Totally Wrong About Who's Spreading Coronavirus, WHO Says
The World Health Organization now says asymptomatic transmission of coronavirus is "very rare."
Throughout the COVID-19 pandemic, we have struggled to keep up with evolving guidelines from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) as they work to slow the spread of the novel coronavirus. There is still so much we don't know about the virus, and we learn new things every day—some of which even contradicts earlier information. The latest news from WHO, however, is particularly jarring, because it seems to go against so much of what we have come to believe about COVID-19 transmission. According to new data, WHO is now saying asymptomatic transmission of coronavirus is "very rare."
"From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual," Maria Van Kerkhove, PhD, head of WHO's emerging diseases and zoonosis unit, said at a United Nations briefing on June 8. "It's very rare."
These remarks are in line with the face mask guidelines WHO released on June 5, which stated, "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."
If true, this could change everything about our collective response to coronavirus. So much of how we have handled the pandemic—from the widespread use of face masks to social distancing measures to school closures—has been based on the belief that individuals without symptoms can still transmit the virus. And while WHO is not denying the possibility of asymptomatic spread, they are certainly downplaying it.
Van Kerkhove also downplayed the number of truly asymptomatic cases. "The other thing we're finding is that when we actually go back and say, 'How many of them were truly asymptomatic?'—we find out that many have really mild disease," she said. "They're not 'COVID' symptoms, meaning they may not have developed fever yet. They may not have had a significant cough, or they may not have shortness of breath, but some may have mild disease."
It's important to note that Van Kerkhove's remarks and WHO's current guidelines contradict previous reports about the spread of COVID-19. In May, the CDC said that 35 percent of people with coronavirus never develop symptoms, and they estimated that 40 percent of infections were from asymptomatic carriers. Other studies have placed the rate of asymptomatic coronavirus cases at as high as 80 percent.
In their June 5 mask guidelines, WHO admits that viable virus has been found in asymptomatic and pre-symptomatic people, meaning that transmission is possible. The organization also acknowledges past studies have appeared to show significant rates of asymptomatic and pre-symptomatic spread. But, WHO concludes, "the available data, to date, on onward infection from cases without symptoms comes from a limited number of studies with small samples that are subject to possible recall bias and for which fomite transmission [infection from touching an object with viral particles on it] cannot be ruled out."
It's also important to draw a distinction between asymptomatic people (those who never develop noticeable coronavirus symptoms) and pre-symptomatic people (those who are infected but have yet to develop symptoms). The CDC's estimate of 40 percent of transmissions coming from people without symptoms includes both asymptomatic and pre-symptomatic individuals. While Van Kerkhove did mention pre-symptomatic people in her remarks, she mostly used the term asymptomatic.
But WHO appears to be conflating the two terms, suggesting that the vast majority of people spreading coronavirus are those with COVID-19 symptoms. "What we really want to be focused on is following the symptomatic cases," Van Kerkhove said. "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]."
So, does that mean you should go back to living your life as you did pre-pandemic and simply self-isolate if you feel sick? Not so fast. With new information about the coronavirus emerging daily, the latest report from WHO is just one more piece of data to keep in mind while assessing personal risk. At the same time, if more studies emerge suggesting that asymptomatic spread is a true rarity, national guidelines may change accordingly. And for current CDC guidelines to follow, here are 5 Things the CDC Says You Still Shouldn't Be Doing.