Thread by @McDevonMD

1/ It's becoming clearer that 10 days of isolation for severe COVID is not sufficient.

In this study, virus was cultured from predominantly NP samples 3-4 weeks after symptom onset. Only 7 of the 87 patients with severe disease were admitted to ICU (i.e. most were on the ward).

https://twitter.com/GermHunterMD/status/1363879901909053441

2/ Here's another preprint suggesting persistently high viral load in LRT samples through to 10 days following symptom onset (the period sampled though it seems reasonable to extrapolate beyond this given no downward trend) in severe disease:

https://twitter.com/DFisman/status/1363528025791422469

3/ It strikes me that a crucial point is how to define severe disease vis-a-vis duration of isolation precautions.

NIH (and most of the relevant studies) define SpO2 <94% on room air as severe disease - this would include most ward patients in Ontario.

covid19treatmentguidelines.nih.gov/overview/clini…

4/ But @PublicHealthON IPAC guidelines are incongruent with this, and lump hospitalized patients in with "mild to moderate" disease, for which only 10 days of isolation precautions are recommended.

publichealthontario.ca/-/media/docume…

5/ My sense of the literature was that only 10 days of isolation for ward patients on supplemental O2 was on shaky ground before these recent studies.

Together with this small n study suggesting a longer duration of viral shedding in B.1.1.7 cases...

https://twitter.com/EricTopol/status/1362049551490637834

6/ ... and increasing prevalence of B.1.1.7, I think we urgently need to update the @PublicHealthON guidelines on duration of isolation precautions for ward patients requiring supplemental O2, who should be considered "severe" for this purpose in alignment with the literature.

@threadreaderapp unroll

Circling back to clarify that this study included similar numbers of "severe illness" and "critical illness" per NIH definitions, which were collectively analyzed as "severe disease" (vs "non-severe disease," which included asymptomatic, mild, and moderate illness).