I am deeply confused how a serial interval can be negative. If I understand the words involved that means you spread it on to someone who gets their symptoms before you do?
If I understand that correctly, it means you’re breathing out infectious levels of virus days before you cough / notice that you are sick.
(I’m confused about your confusion, because I thought the negative serial interval of COVID was one of its most striking features, and the reason why many of the old ‘control system’ things failed; like, people were used to “if you feel fine you are fine” and wouldn’t accept “everyone needs to act as though they could be sick, because you won’t know whether or not you’re infectious until after the fact.”)
Yes, I get the idea that you can spread the disease before you show symptoms, but this would be the person you infect showing symptoms before you do, as an expectation, which does seem super weird.
Or another framing: The question is, how long is the time between being infected and then infecting someone else? And the answer might be smaller than the time before you show symptoms, but if it’s negative the virus is doing something involving time travel.
The ‘generation time’ is the one that can’t be negative. Suppose Alice gets infected on day 1, infects Bob on day 2, Bob shows symptoms on day 3, and Alice shows symptoms on day 4. We end up with:
Incubation periods of 3 days (for Alice) and 1 day (for Bob)
Generation times of 1 day (Bob infected—Alice infected)
Serial intervals of −1 day (Bob symptoms—Alice symptoms)
Or another framing: The question is, how long is the time between being infected and then infecting someone else? And the answer might be smaller than the time before you show symptoms, but if it’s negative the virus is doing something involving time travel.
They seem to be referring to the serial interval between symptom onset.
Which indeed can’t be negative on average. But they write it was only negative in 21.6% of cases. And there is no rule stating there can’t be cases where it’s negative (as long as you have transmission before symptoms).
If I understand that correctly, it means you’re breathing out infectious levels of virus days before you cough / notice that you are sick.
(I’m confused about your confusion, because I thought the negative serial interval of COVID was one of its most striking features, and the reason why many of the old ‘control system’ things failed; like, people were used to “if you feel fine you are fine” and wouldn’t accept “everyone needs to act as though they could be sick, because you won’t know whether or not you’re infectious until after the fact.”)
Yes, I get the idea that you can spread the disease before you show symptoms, but this would be the person you infect showing symptoms before you do, as an expectation, which does seem super weird.
Or another framing: The question is, how long is the time between being infected and then infecting someone else? And the answer might be smaller than the time before you show symptoms, but if it’s negative the virus is doing something involving time travel.
The ‘generation time’ is the one that can’t be negative. Suppose Alice gets infected on day 1, infects Bob on day 2, Bob shows symptoms on day 3, and Alice shows symptoms on day 4. We end up with:
Incubation periods of 3 days (for Alice) and 1 day (for Bob)
Generation times of 1 day (Bob infected—Alice infected)
Serial intervals of −1 day (Bob symptoms—Alice symptoms)
They seem to be referring to the serial interval between symptom onset. Which indeed can’t be negative on average. But they write it was only negative in 21.6% of cases. And there is no rule stating there can’t be cases where it’s negative (as long as you have transmission before symptoms).