Thread by @LongDesertTrain

1/6 Important new study from Japan finds that with Omicron, infectious viral loads peak 3-6 days after symptom onset/diagnosis.

So many people are ending isolation & returning to work & school at peak infectiousness. Thanks, @CDCgov.

h/t @gianlucac1
niid.go.jp/niid/en/2019-n…

2/6 They looked at 21 cases: 19 vaxxed, 2 unvaxxed, 17 symptomatic, 4 asymptomatic. For the symptomatic, viral loads (by PCR Ct value) were much higher on days 3-6 after symptom onset than days -1 to 2. Furthermore, many samples still had high viral loads on days 7-9.

3/6 This is very different than what we'd seen with previous variants. Studies by @LucaFerrettiEvo, @DiseaseEcology, & others showed that peak infectiousness previously occurred the day before symptom onset & fell fairly rapidly thereafter. medrxiv.org/content/10.110…

4/6 Before people start shouting about Ct values measuring dead RNA fragments, note that the researchers cultured virus from these samples, and the results mirrored those for Ct value: peak levels of live virus on days 3-6 & significant amounts of live virus on days 7-9.

5/6 Will the CDC "follow the science" & revise their 5-day, no-exit-test isolation period in light of these results? Or was that guideline based entirely on political & economic considerations (i.e. the desires of the wealthy & well-connected political donors)? Take a guess.

6/6 I know @michaelmina_lab discussed the tendency for infectiousness to peak later (relative to symptom onset) in a population with widespread immunity compared to a naive pop, but I can't find the tweet. This + short incubation period may largely explain this study's findings.

7/ Adding this from @LazarusLong13: Taiwan rejects shortening of the 10-day isolation period based on viral load measurements (based on Ct value). They didn't culture to detect live virus, but their Ct results match very well w/the Japan study.

https://twitter.com/LazarusLong13/status/1477194315512246272

8/ Who has more credibility and a better track record when it comes to Covid, the U.S. CDC or Taiwan's CECC? 🤔🤔

https://twitter.com/BarryHunt008/status/1477105766574272520