The Belgian woman developing symptoms 11 days after coming back from Egypt suggests that the disease timeline is substantially longer than with Delta. This makes me think immunity escape plays a very big factor in how it was able to outcompete Delta this quickly in South Africa. (But obviously there could also be a missing piece or misinformation in the Egypt-Belgium story.)
I have to assume the 11 day delay is unusual, or even that perhaps that case didn’t actually come from Egypt. If it usually took 11 days then there’s no way it grows this fast (and if it still does, seriously, it’s time to give up.)
Based on the report it seems that someone arriving Nov 11 had enough virus to test positive by Nov 13, and the person he infected had enough virus to test positive on Nov 18. Both were sent to the hospital but it is unclear whether this was part of a standard procedure or if they were ill enough to need to go.
Both were sent to the hospital but it is unclear whether this was part of a standard procedure or if they were ill enough to need to go.
Testing positive was sufficient to get them sent to the hospital, and they had mandatory PCR testing every ~3 days; this is no evidence about their symptoms.
(I recently went through HK arrival quarantine—in the same hotel, no less—and researched the operating procedure runbook out of personal interest.)
Why does it follow that a longer time to develop symptoms suggests immune escape?
Also, if the timeline is longer, then the estimates of how much more transmissible Omicron is, based on the time it’s taken for it to displace Delta, should be even greater, right?
The speed by which Omicron outcompeted Delta is explained by three broad contributors: - Generation time - Immunity escape - Transmissibility in susceptible populations
We learn (probabilistically) that the first factor isn’t lower than in Delta, and may even be higher (longer generation time). This leaves even more work to be done for the other two factors. You’re right that in theory, Omicron could just be crazy good at spreading in susceptible populations. However, I think that’s unlikely on priors given that you get an easy 3x increase in overall transmissibility with full immune escape, and that seems easier, mutation-wise, than the virus suddenly turning into something that’s a lot more transmissible than any coronavirus we’ve ever seen.
On the other hand, if it takes longer to show symptoms but it’s still equally transmissible since early but for longer, you get higher Rs without surprising new mechanisms of transmission. Also, it may also be escaping our current precautions instead of the immunity.
The Belgian woman developing symptoms 11 days after coming back from Egypt suggests that the disease timeline is substantially longer than with Delta. This makes me think immunity escape plays a very big factor in how it was able to outcompete Delta this quickly in South Africa. (But obviously there could also be a missing piece or misinformation in the Egypt-Belgium story.)
I have to assume the 11 day delay is unusual, or even that perhaps that case didn’t actually come from Egypt. If it usually took 11 days then there’s no way it grows this fast (and if it still does, seriously, it’s time to give up.)
11 days could be unusual based on the Hong Kong report:
https://www.news.gov.hk/eng/2021/11/20211123/20211123_102145_582.html?type=category&name=covid19&tl=t
Based on the report it seems that someone arriving Nov 11 had enough virus to test positive by Nov 13, and the person he infected had enough virus to test positive on Nov 18. Both were sent to the hospital but it is unclear whether this was part of a standard procedure or if they were ill enough to need to go.
Testing positive was sufficient to get them sent to the hospital, and they had mandatory PCR testing every ~3 days; this is no evidence about their symptoms.
(I recently went through HK arrival quarantine—in the same hotel, no less—and researched the operating procedure runbook out of personal interest.)
Internet is a great place. Thanks for that info!
Why does it follow that a longer time to develop symptoms suggests immune escape?
Also, if the timeline is longer, then the estimates of how much more transmissible Omicron is, based on the time it’s taken for it to displace Delta, should be even greater, right?
The speed by which Omicron outcompeted Delta is explained by three broad contributors:
- Generation time
- Immunity escape
- Transmissibility in susceptible populations
We learn (probabilistically) that the first factor isn’t lower than in Delta, and may even be higher (longer generation time). This leaves even more work to be done for the other two factors. You’re right that in theory, Omicron could just be crazy good at spreading in susceptible populations. However, I think that’s unlikely on priors given that you get an easy 3x increase in overall transmissibility with full immune escape, and that seems easier, mutation-wise, than the virus suddenly turning into something that’s a lot more transmissible than any coronavirus we’ve ever seen.
Makes sense to me...
On the other hand, if it takes longer to show symptoms but it’s still equally transmissible since early but for longer, you get higher Rs without surprising new mechanisms of transmission. Also, it may also be escaping our current precautions instead of the immunity.