• Implications of Shortened Quarantine Among Household Contacts of Index Patients with Confirmed #SARS-CoV-2 Infection — Tennessee and Wisconsin, April–September 2020 | MMWR
    https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a1.htm

    Au sein des foyers familiaux, 19% des cas secondaires (PCR positif) n’apparaissent que 7 jours après l’apparition des symptômes du cas (supposé) source.

    Summary

    What is already known about this topic?

    After exposure to COVID-19, a 14-day quarantine period can prevent further spread but might be challenging to maintain.

    What is added by this report?

    Among persons exposed to COVID-19 in the household who were asymptomatic and had negative laboratory test results through 7 days after symptom onset in the index patient, 19% experienced symptoms or received positive test results in the following week.

    What are the implications for public health practice?

    A shorter quarantine after household exposure to COVID-19 might be easier to adhere to but poses some risk for onward transmission. Persons released from quarantine before 14 days should continue to avoid close contact and wear masks when around others until 14 days after their last exposure.

    [...]

    The findings in this report are subject to at least five limitations. First, the index patient’s illness onset date was used as a proxy for last exposure. This might not have been the actual date of last exposure, affecting calculations on timing of positive specimens and symptom onset. Second, chains of transmission are challenging to recreate with observational studies; however, the main findings were robust in several sensitivity analyses designed to account for possible misclassification of secondary infections. Third, household contacts were assumed to have acquired infection from the index patient; however, the possibility that some infections might have been introduced from the community cannot be excluded. Fourth, a highly sensitive assay was used to detect SARS-CoV-2 nucleic acids; in some settings, however, this type of testing might not be available or yield timely results. Finally, these findings might not be directly translatable to use of point-of-care assays, which yield more rapid results but with lower sensitivity.