Add Lancet meta-analysis finding no transmissible virus after 9 days

README.md

@@ -386,6 +386,8 @@ Note that the WHO will generally be unable to make statements that their more pr
 * [Declining prevalence of antibody positivity to SARS-CoV-2: a community study of 365,000 adults](https://www.medrxiv.org/content/10.1101/2020.10.26.20219725v1) was found as part of the [REACT2 study](https://www.imperial.ac.uk/medicine/research-and-impact/groups/react-study/), echoing [findings from seroprevalence in blood donors in England](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/923668/Weekly_COVID19_Surveillance_Report_week_40.pdf) (see pages 41 to 44)
 * [SARS-CoV-2 seroprevalence trends in healthy blood donors during the COVID-19 Milan outbreak](https://www.medrxiv.org/content/10.1101/2020.05.11.20098442v1.full), finding that among blood donors in Milan, Lombardy, around 4.6% were positive to IgG at the "start of the outbreak" on February 24, and around 7.1% by April 8, using a test with 98.3% specificity, yielding similar prevalence as a [Seroprevalence of SARS-CoV-2 in Hong Kong and in residents evacuated from Hubei province, China: a multicohort study](https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247\(20\)30053-7/fulltext) despite different specificity and sensitivity of tests
 * [Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals](https://www.sciencedirect.com/science/article/pii/S0092867420306103), published on Cell, finds that T-cells from uninfected individuals respond to SARS-CoV-2, "suggesting cross-reactive recognition between circulating ‘common cold’ coronaviruses and SARS-CoV-2", echoing a previous preprint [Presence of SARS-CoV-2 reactive T cells in COVID-19 patients and healthy donors](https://www.medrxiv.org/content/10.1101/2020.04.17.20061440v1); however, a newer preprint claims [Pre-COVID-19 humoral immunity to common coronaviruses does not confer cross-protection against SARS-CoV-2](https://www.medrxiv.org/content/10.1101/2020.08.14.20173393v1)
+* [SARS-CoV-2, SARS-CoV, and MERS-CoV viral load dynamics, duration of viral shedding, and infectiousness: a systematic review and meta-analysis](https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(20)30172-5/fulltext) finds that mean duration of RNA shedding is 17 days, but no study detected live virus beyond day 9 of illness, despite persistently high viral loads from RT-PCR cycles
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 ## Follow-up