News & Views: What Do We Know about COVID-19 Transmission at This Juncture?
Published on in Vaccine Update for Healthcare Providers
Published on in Vaccine Update for Healthcare Providers
In early July 2020, news reports discussed a seeming difference of opinion between scientists and the World Health Organization (WHO). At its core the difference related to whether or not SARS-CoV-2 can spread through aerosolized droplets, and it wasn’t so much a “rift” as it was the process of scientific discourse. But, given the pandemic and lack of tools to control it, the discourse resulted in pressure that led more than 200 scientists to support an open letter stating that there was enough evidence of aerosolized spread that the WHO should be including it in communications about COVID-19 transmission. The scientists convinced the WHO to make this update, but the discussion may have created questions and left some of your patients wondering what we know about transmission of SARS-CoV-2 at this point?
Almost since its inception, COVID-19 has been characterized as most commonly spreading in manners similar to other respiratory infections — through large respiratory droplets and contact with infected surfaces followed by touching one’s face. Coughing, sneezing, and even talking or singing can cause droplets containing infectious virus particles to spread to others or contaminate surfaces.
However, as described in the open letter, evidence also suggests small droplet spread. In terms of infection control, the difference between large and small droplet transmission is critical. Small droplets, defined as 5 microns or smaller, mean that the virus can spread through the air. As a result, decreasing transmission relies more heavily on ventilation and isolation, particularly because these droplets can travel longer distances and may hang in the air after an infected person has left.
Whereas large droplets are unlikely to travel more than 3 to 6 feet, small droplets can travel more than 10 to 13 feet. In practical terms, this means that people in the same room could be infected even without directly interacting. When considering how to stem transmission of COVID-19, this type of spread has implications for reopening places like restaurants and schools, where groups of people gather in small spaces. This was one of the reasons that the scientists felt the open letter was timely.
Takeaways for talking with patients:
One of the underlying themes of transmission is the idea that people who don’t have symptoms can spread COVID-19. While it remains unclear whether asymptomatic individuals can transmit the virus, it is clear that people who experience symptoms can spread the virus beginning about two days before symptoms start. And, people can spread virus throughout the period during which they are symptomatic. Symptoms typically occur within two days to two weeks of exposure, but it has varied in studies from different regions.
Takeaways for talking with patients:
Contributed by: Charlotte A. Moser, MS, Paul A. Offit, MD
Categories: Vaccine Update July 2020, News and Views About Vaccines
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