1/ Clearing up confusion about what it means that Delta viral loads are ~1000x higher than the viral loads seen with the original SARS-CoV-2.
medpagetoday.com/special-report…
medpagetoday.com/special-report…
2/ We need to be precise in speaking about infectiousness.
Exposure = Dose x Time
If viral loads in infected people are ~1000x higher with Delta than original SARS-CoV-2, the dose of virus to which the uninfected person is exposed has gone up ~1000x.
Exposure = Dose x Time
If viral loads in infected people are ~1000x higher with Delta than original SARS-CoV-2, the dose of virus to which the uninfected person is exposed has gone up ~1000x.
3/ Exposure = Dose x Time
If Dose increases 1000x
the Exposure you would have gotten from an infected person early in the pandemic over 15 minutes
you now get in 0.9 seconds (~1 second).
15 minutes = 900 seconds
But in NEITHER scenario are you 100% sure to be infected.
If Dose increases 1000x
the Exposure you would have gotten from an infected person early in the pandemic over 15 minutes
you now get in 0.9 seconds (~1 second).
15 minutes = 900 seconds
But in NEITHER scenario are you 100% sure to be infected.
4/ The relationship between Exposure and onward transmission (R0) is not linear.
R0 = # of people infected by someone with SARS-CoV-2
R0 for the original SARS-CoV-2: ~2
R0 for Alpha: ~3
R0 for Delta: ~4-5
R0 = # of people infected by someone with SARS-CoV-2
R0 for the original SARS-CoV-2: ~2
R0 for Alpha: ~3
R0 for Delta: ~4-5
5/ Dose of virus to which people are exposed may have increased by 1000x, but that doesn't mean 1000x as many people will be infected.
Put another way,
Alpha is 50% more infectious than the original SARS-CoV-2.
Delta is 50% more infectious than Alpha.
Put another way,
Alpha is 50% more infectious than the original SARS-CoV-2.
Delta is 50% more infectious than Alpha.
6/ You don't need an R0 of 1000 for a virus to be bad news.
When you've got exponential spread, an R0 of 4 is really really bad (as is an R0 of anything more than 1, which means the epidemic is expanding).
theguardian.com/world/datablog…
When you've got exponential spread, an R0 of 4 is really really bad (as is an R0 of anything more than 1, which means the epidemic is expanding).
theguardian.com/world/datablog…
7/ But this is what it means that fleeting contact with someone CAN (not will) lead to SARS-CoV-2 transmission.
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