COVID-19 Quarantines: U.S. CDC Issues Warnings About Shortened Quarantines As Some Transmission Of SARS-CoV-2 Occurs After 7 Or 10 Days
: The U.S. CDC has published a new warning that there is some onward transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from household contacts released from quarantine after seven or 10 days and that extra precautions still need to be adhered to.
The U.S. CDC warning was issued after a study was published in the Jan. 1 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report. https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a1.htm
Dr Melissa A. Rolfes, Ph.D., from the CDC COVID-19 Response Team, and colleagues analyzed interim data from an ongoing study of household transmission of SARS-CoV-2 to examine the proportion of household contacts who had detectable virus after a shortened quarantine period. For 14 days, household contacts of index patients completed a daily symptom diary and self-collected respiratory specimens, which were tested for SARS-CoV-2.
The study team found that 59 percent of the 185 household contacts had detectable SARS-CoV-2 at any time; 76 and 86 percent of test results were positive within seven and 10 days, respectively, after the index patient's illness onset date. The chance of remaining asymptomatic and receiving negative test results through day 14 was 81 and 93 percent, respectively, among household contacts who received negative SARS-CoV-2 test results and were asymptomatic through day 7 or through day 10.
Dr Rolfes told Thailand Medical News, "Although persons might be more adherent to a shorter quarantine period, such a policy is not without risk for further spread. Timely access to a sufficiently sensitive test at the end of a shorter quarantine period will help identify household contacts with SARS-CoV-2 infection."
Quarantine can stop onward transmission of SARS-CoV-2; however, adherence to a 14-day quarantine can be challenging. Analysis of data from an ongoing study of SARS-CoV-2 detection after exposure to an infected household member found an 81% chance that a household contact who had negative SARS-CoV-2 RT-PCR test results and was asymptomatic for 7 days after the index patient’s illness onset date would remain asymptomatic and continue to receive negative RT-PCR test results through 14 days. Conversely, one in five household contacts would become symptomatic or receive positive SARS-CoV-2 RT-PCR test results between day 7 and 14, suggesting that, compared with no quarantine, reducing quarantine to <14 days might decrease but not eliminate the risk for spreading SARS-CoV-2.
However with consistent adherence, quarantine prevents transmission from persons who were exposed to the virus and who might become infectious, but who do not have symptoms or signs of infection (i.e., who are presymptomatic or who will remain asymptomatic).
The length of quarantine is typically based on the known incubation period, or the interval between exposure to an infectious pathogen and the development of symptoms or signs of infection, which for SARS-CoV-2 ranges from 2 to 14 days. https://www.cdc.gov/coronavirus/2019-ncov/hcp/faq.html#Transmission
However, quarantine efforts will not effectively reduce transmission if adherence is low.
Evidence suggests that adherence to recommended quarantine during the COVID-19 pandemic varies and might be low in some settings. https://pubmed.ncbi.nlm.nih.gov/33040761/
France, Belgium, and now some jurisdictions in the United States have shortened the quarantine period for persons exposed to someone with COVID-19 from 14 days to 10 or 7 days, but there is ongoing concern that shortening quarantine for all exposed persons could increase community transmission. https://pubmed.ncbi.nlm.nih.gov/33045184/
Modeling studies suggest that combining a shorter quarantine with a timely diagnostic test at the end, to detect asymptomatic or presymptomatic infections, might carry some residual risk for transmission but could be an alternative to a 14-day quarantine period if the shorter quarantine length enhances compliance.
A 14-day quarantine of all close contacts who are exposed to a person with COVID-19, such as in the household, is the most effective strategy to reduce the spread of COVID-19. Although persons might be more adherent to a shorter quarantine period, such a policy is not without risk for further spread. Timely access to a sufficiently sensitive test at the end of a shorter quarantine period will help identify household contacts with SARS-CoV-2 infection and might enable an effective shorter quarantine period for household contacts who remain asymptomatic and have negative test results, who pose lower risk for further spread of COVID-19.
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