A large-scale retrospective cohort study in the UK examined SARS-CoV-2 2,974,596 contacts of 1,064,004 index cases between September 1, 2020 and February 28, 2021 in England within 10 days of index case positive test. They found that infectivity increased with increased index case viral load/lower Ct (11.7% transmission to contacts at Ct=15 and 4.5% at Ct=30) and that infection with B.1.1.7 increased transmission 1.55 fold. Transmission was most likely in household contacts and household visitors and least likely after outdoor contact, with children being less likely than adults to test positive or transmit infection (Figure 2).

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In a letter to the editor, infectious disease researchers associated with the University of Melbourne and Royal Melbourne Hospital present a case study of a 63-year-old HIV-positive male with SARS-CoV-2 RNA detected in RT-PCR of sputum on day 5 of symptoms and of feces on day 9. By day 53, when all RT-PCR were negative, neutralizing antibody development was detected and persisted at day 116 (Figure 1). These results indicate virus isolation in feces after respiratory cultures, suggesting that fecal-oral transmission of SARS-CoV-2 may still be a risk even after respiratory sputum samples are negative.

A research brief by researchers affiliated with G. D'Annunzio University of Chieti-Pescara and Spirito Hospital of Pescara, Italy discusses 7 health care workers (HCWs) who tested positive for SARS-CoV-2 after receiving both doses of the BNT162b2 vaccine between January - March 2021, all of whom were asymptomatic within 36 days of the second vaccination (Table 1). This highlights that despite vaccination, HCWs should maintain precautions to avoid spread of infection, although larger studies are still necessary.