Concerning COVID: Defining “Close Contacts”

October 5, 2020 |

Concerning COVID

October 5, 2020

Question: For contact tracing, why do we define “close contacts” as anyone who has been within 6 feet for at least 15 minutes within two days before the person developed symptoms?


“Quarantine is used to keep someone who might have been exposed to COVID-19 away from others. Quarantine helps prevent spread of disease that can occur before a person knows they are sick or if they are infected with the virus without feeling symptoms. People in quarantine should stay home, separate themselves from others, monitor their health, and follow directions from their state or local health department.”

Since no masks outside of N95s prevent transmission of all viral particles, people are still considered close contacts regardless of whether or not masks were worn by both parties. This allows health authorities to track community spread more accurately

“What counts as close contact?”

  • You were within 6 feet of someone who has COVID-19 for a total of 15 minutes or more
  • You provided care at home to someone who is sick with COVID-19
  • You had direct physical contact with the person (hugged or kissed them)
  • You shared eating or drinking utensils
  • They sneezed, coughed, or somehow got respiratory droplets on you


  • Center for Disease Control and Prevention. (2020, September 10). COVID-19: When to Quarantine.
  • Koks S, Williams RW, Quinn J, Farzaneh F, Conran N, Tsai SJ, Awandare G, Goodman SR. (2020). COVID-19: Time for precision epidemiology. Experimental Biology and Medicine. 245 (8). https://doi: 10.1177/1535370220919349.

Fact Summary:
The CDC defines “close contact” under these parameters because 2 days is the minimum amount of time for an individual to present symptoms after being exposed to COVID-19 (CDC, 2020). The CDC recommends that individuals that fall under “close contact” parameters should quarantine. Quarantining those individuals helps to mitigate the potential spread of the virus. Under the “domino model,” (Koks et al., 2020) a single individual has a transmission rate of infecting two people, giving a total infected population of over a million in two weeks. However, taking away half of the “dominos” every three days by limiting close contact reduces the total infected population after two weeks to less than five thousand.

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