Trending Clinical Topic: COVID-19 Transmission

Ryan Syrek


October 02, 2020

Each week, we identify one top search term, speculate about what caused its popularity, and provide an infographic on a related condition. If you have thoughts about what's trending and why, share them with us on Twitter or Facebook. Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Since the start of the COVID-19 pandemic, researchers have attempted to identify the most common means by which SARS-CoV-2 is spread. This week, an ongoing review of transmission methods resulted in the top trending clinical topic.

On Friday, September 18, the Centers for Disease Control and Prevention (CDC) updated its information on coronavirus spread to acknowledge the prominence of aerosol transmission. However, the following Monday, the CDC removed that information from its website. At the time of publication, that site now states that the organization "is currently updating its recommendations regarding airborne transmission of SARS-CoV-2."

The CDC's now-deleted update stated that the virus is spread "through respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks, or breathes. These particles can be inhaled into the nose, mouth, airways, and lungs and cause infection. This is thought to be the main way the virus spreads." The text had also explained that evidence suggests that droplets and airborne particles suspended in air may be breathed in by others and travel distances farther than 6 feet.

The World Health Organization (WHO) also has yet to officially declare aerosols as a definitive contributor in the spread of COVID-19. Thus far, the WHO suggests only that airborne transmission may play a role in infection, especially in poorly ventilated rooms and buildings. Subsequently, the physical distancing measures necessary to prevent disease spread have become a subject of debate. The WHO has called for separation of at least 1 meter (around 3 feet), whereas the CDC has recommended 6 feet or more. Although some evidence has suggested that SARS-CoV-2 droplets can reach as far as 26 feet after violent exhalations like coughs or sneezes, experts generally agree that transmission is not highly likely at that distance. Optimal distancing has yet to be determined, but the use of face masks has been conclusively proven to help control the spread of coronavirus droplets and aerosols.

In terms of other potential means of transmission, a recent study found extensive environmental contamination of SARS-CoV-2 RNA within 24 hours in occupied rooms of two persons who were asymptomatic. COVID-19 spread by indirect contact was identified in a cluster of infections at a shopping mall in China, although no clear proof of infection due to a contaminated environment was found. The CDC states that transmission by touching a surface or object with the virus and then touching one's mouth or eyes is possible. However, the website clarifies: "This is not thought to be the main way the virus spreads." Infectious SARS-CoV-2 was also recently confirmed in the feces of a patient with severe COVID-19.

Because effective prevention strategies rely heavily on a firm understanding of the most common means of transmission, further information about how COVID-19 is spread is likely to result in amended guidance. As more evidence emerges, the subject will remain one of the top trending clinical topics.

Read more clinical information about COVID-19.


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