It's not as rare as a misunderstanding on Monday led people to believe.
Plenty of parents and teachers are worried about how COVID-19 could spread in school settings, so a suggestion that asymptomatic spread of the virus is 'very rare' piqued the interest of many this week. Unfortunately, the reasons why public health experts have emphasized social distancing during the pandemic still stand, because people can spread the virus without even knowing they are sick or showing symptoms.
On Monday, a World Health Organization official stated that the spread of the virus from asymptomatic people is very rare...but by Tuesday the WHO was walking back the claim.
The clarification comes after experts disagreed with the Van Kerkhove's suggestion on Monday.
Liam Smeeth, a professor of clinical epidemiology at the London School of Hygiene and Tropical Medicine, says Van Kerkhove's statements shocked him. "I was quite surprised by the WHO statement," he explained. "It goes against my impressions from the science so far that suggest asymptomatic people—who never get symptoms—and pre-symptomatic people are an important source of infection to others."
Dr. Maria Van Kerkhove, head of WHO's emerging diseases and zoonosis unit, originally told reporters on Monday, "From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual. It's very rare."
But by Tuesday Van Kerkhove said there had been "misunderstandings" regarding her Monday statement and clarified that what she was referring to as "very rare" was a subset of studies, not asymptomatic transmission globally. She also added, "Some estimates of around 40% of transmission may be due to asymptomatic, but those are from models, and so I didn't include that in my answer yesterday but wanted to make sure that I covered that here."
The science is evolving to catch up with the virus, and experts suggest that distinguishing between asymptomatic, pre-symptomatic and paucisymptomatic (presenting few symptoms) is important here.
"Detailed contact tracing from Taiwan as well as the first European transmission chain in Germany suggested that true asymptomatics rarely transmit. However, those (and many other) studies have found that paucisymptomatic transmission can occur, and in particular, in the German study, they found that transmission often appeared to occur before or on the day symptoms first appeared," Dr. Babak Javid, a principal investigator at Tsinghua University School of Medicine in Beijing and consultant in infectious disease at Cambridge University Hospitals, said this week.
Bottom line: The science suggests that we need to focus on testing, tracing and quarantining those with symptoms rather than living in fear of asymptomatic spread, but we do need to recognize that asymptomatic spread is a possibility.
As first reported by CNBC, the Centers for Disease Control has previously suggested that it's necessary for people to remain socially distant even from those who don't have symptoms because the symptomless people can spread the virus. The CDC notes: "The potential for presymptomatic transmission underscores the importance of social distancing, including the avoidance of congregate settings, to reduce COVID-19 spread."
We do need to continue keeping our distance, at least for now.
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