Research released in CDC report
An investigation conducted by Vermont Dept. of Health scientists and released by the Centers for Disease Control and Prevention found that transmission of Covid-19 can occur during multiple brief exposures with someone who is infected.
Staff from the Health Dept. and the Dept. of Corrections looked into an instance in which a state corrections officer became infected after several brief interactions with incarcerated people who had Covid-19. None of the individual interactions lasted 15 minutes, but together added up to more than that amount over time.
CDC officials cited the investigation findings in announcing its updated definition of what is considered to be a close contact. The Vermont report was published in the CDC’s Morbidity and Mortality Weekly on Oct. 21.
The CDC definition now says a close contact is someone who was within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period. This is a refinement of previous guidance, which defined close contact as being within 6 feet for 15 minutes or more at a time.
The investigation team reviewed video surveillance footage to determine that the correctional officer did not meet the then-definition of a close contact. The team reviewed additional footage and standard correctional officer shift duty responsibilities to approximate the frequency and duration of interactions between the correctional officer and infectious incarcerated or detained persons at the facility.
Health Commissioner Mark Levine, MD said he is pleased the CDC is taking this data into account, to increase understanding about the importance of maintaining physical distance.
“Throughout the pandemic, we have let the science lead the way,” said Dr. Levine. “Amid their non-stop work on the Covid-19 response, our team has also contributed to the worldwide body of knowledge about Covid-19. I’m really proud of their work.”
An author on the study, Natalie Kwit, DVM, state public health veterinarian, noted that the key finding that the correctional officer did not initially meet the definition of a close contact, will help public health officials better identify people who could be at risk for getting and spreading Covid-19.
“Vermont is already doing this to a certain degree, but all public health officials can consider this research when doing contact tracing and interviews,” Dr. Kwit said. “It may be more relevant in certain group and congregate settings, where there is potential to have these multiple brief interactions.”
Dr. Kwit emphasized that identifying a close contact is about more than just the length of time of an exposure. How far away a person is, whether they are symptomatic, and their environment are all factors that need to be considered.
“It may expand the number of close contacts identified in certain situations, but is also serves as a reminder of how important it is for people to do the best they can to avoid possible exposure,” said Dr. Kwit. “We all know the key things to do, wear a mask and stay physically distant. But especially as we start to spend more time indoors it’s important to avoid crowds and large gatherings whenever possible.”