After claiming on Monday that asymptomatic transmission of SARS-CoV-2 is “very rare”, World Health Organization Scientist Dr. Maria Van Kerkhove has clarified her meaning:

It was certain that asymptomatic infection happened, she said, but how often was still one of the great unknowns about Covid-19 that scientists were investigating. One of the complications is that some people who appear to be infected but asymptomatic are in fact pre-symptomatic – they can go on to, for instance, experience a mild course of disease. “They may not register that they are sick,” she said.

While it appears there is no new data for the WHO’s statement, at issue is the difference between asymptomatic (infected people who never experience symptoms) and presymptomatic (infected people who WILL experience symptoms but not at the time of the test). Together, asymptomatic and presymptomatic transmission are responsible for almost half of the viral spread and there is insufficient data separating the 2 groups.

Because it’s not currently possible to tell who is infected, and who will spread the virus and become symptomatic (or even severely ill), preventive recommendations including masks, hand washing, physical distancing, contact tracing and isolation remain the tools of choice for preventing transmission. 

The best breakdown we have found is from Dr. Carl Bergstrom (click on this link or on the image below to see the full thread).


  • Continue with physical distancing, hand hygiene, mask-wearing, and other preventative measures as you are able.
  • Always consider the preponderance of evidence. No major decision should be made or risk taken on the basis of one statement, study, or piece of evidence if it runs counter to the majority of other information available.
  • While it’s admittedly disappointing that the WHO muddied the waters with some vague/inaccurate language on June 8th, it’s good to remember that institutions are made of people, and there will be mistakes. This episode should not be used to disregard the other vital services and messages provided by the WHO and other public health organizations.
  • As always, please share this post with your networks.


Sean Hesler, ND lives and practices in Gilbert, AZ. He is a founding member of the Naturopathic Alliance.