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).
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:

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.

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.

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...

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.
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).

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More from @McDevonMD

21 Nov 20
Thread: very useful new systematic review & meta analysis: 1/n

One caveat re: duration of infectiousness is that the cell culture studies almost exclusively looked at naso/oropharyngeal specimens. 2/n
The question is, is cell culture of naso/oropharyngeal specimens an adequate surrogate measure for infectiousness? 3/n
Read 15 tweets
28 Jun 20
I wish I had a bigger follow to promote this paper because I think this kind of research is so important. I just joined twitter, so I don't, but I'll try to do my part anyway. Have a look at: medrxiv.org/content/10.110…
They found that HCWs were identified as cases of COVID at a rate 5.5x nonHCWs (range 2-6 mirroring the epidemic curve), and that 9.8% of HCWs likely transmitted to a household contact. Lots of other stuff in here but these were the findings I found most interesting.
I don't think the available data allowed them to adjust for a differential rate of testing, which was almost certainly higher among HCWs, though I doubt 5.5x higher. On the other hand, the denominator used to calculate rates of identified cases in HCWs was probably over-inclusive
Read 11 tweets

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