COVID-19 Info for SF Healthcare Providers

“LONG” DEFINITION OF CLOSE CONTACT FOR COVID-19 (11/19/2020)

Definition of “close contact” for COVID-19. The SFDPH has adopted the CDC’s updated definition of “close contact” (CDC) for exposure to COVID-19:
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 starting from 2 days before illness onset (or, for asymptomatic patients, 2 days prior to test specimen collection) until the time the patient is isolated.”

A key change to the definition is that the exposure does not have to be 15 consecutive minutes, rather can be cumulative. “Cumulative” means shorter periods are added up over a 24 hour period. For example, three 5-minute exposures make a total of 15 minutes, or dozens of brief encounters over the course of a working shift may add to more than 15 minutes. This new definition is in keeping with our understanding of risk and the chance of getting infected. The CDC’s decision to change the definition was influenced by evidence of COVID-19 acquired by an employee with video documentation of not meeting the old definition while meeting the new definition (Pringle et al).

SFDPH recognizes challenges in implementing this new definition. Recalling, measuring, and adding up brief encounters is difficult. The number of persons categorized as close contacts and requiring quarantine may greatly increase. Moreover, data are limited, making it difficult to precisely define “close contact”. Therefore, SFDPH recommends using cumulative exposure as an operational definition while also taking into account other factors that affect the risk of getting COVID-19. Consistent with CDC guidance (CDC) and other health jurisdictions (CDPH, LACDPH, WSDH), the following factors should also be considered:

• Proximity (closer distance likely increases exposure risk)
• Duration of exposure (longer exposure time likely increases exposure risk)
• Whether the infected individual has symptoms (the period around onset of symptoms is associated with the highest levels of viral shedding; PCR cycle threshold value may also be an indication of viral shedding, see Tom et al)
• If the infected person was likely to generate respiratory aerosols (e.g., was coughing, singing, shouting, talking)
• Environmental factors (e.g., crowding, adequacy of ventilation) and whether exposure was indoors or outdoors (e.g., parents waiting outside to pick up children).

Because the general public has not received training on proper use of respiratory PPE, determining if someone other than healthcare personnel is a close contact should be made irrespective of whether the contact or infected person was wearing respiratory PPE. The use of fabric face coverings should not be used to determine if someone is or is not a close contact.

As previously defined, SFDPH continues to consider the following persons as close contacts regardless of the cumulative time of exposure:

• A person who had direct contact with that person’s body fluids or secretions while they were not wearing a facemask, gown, and gloves
• People in the home of, sex partners of, and people who take care of or are taken care of by the person with COVID-19
• For pods/cohorts of children under 12, SFDPH considers all children and staff in a cohort to be close contacts

References

• California Department of Public Health (CDPH) https://covid19.ca.gov/contact-tracing/
• Centers for Disease Control and Prevention (CDC) close contact definition: https://www.cdc.gov/coronavirus/2019-ncov/php/contact-tracing/contact-tracing-plan/appendix.html#contact
• Los Angeles County Department of Public Health (LACDPH) http://publichealth.lacounty.gov/acd/ncorona2019/IsolationQuarantine/#dCloseContact
• Pringle JC, Leikauskas J, Ransom-Kelly, et al. COVID-19 in a Correctional Facility Employee Following Multiple Brief Exposures to Persons with COVID-19 — Vermont, July–August 2020. MMWR. October 30, 2020; 69(43);1569–1570. https://www.cdc.gov/mmwr/volumes/69/wr/mm6943e1.htm
• Tom MR, Mina MJ. To Interpret the SARS-CoV-2 Test, Consider the Cycle Threshold Value. Clinical Infectious Diseases, ciaa619, https://doi.org/10.1093/cid/ciaa619
• Washington State Department of Health (WSDH), COVID-19 Infection – General: https://www.doh.wa.gov/Portals/1/Documents/5100/420-107-Guideline-COVID-19.pdf