On KCBS Radio today - Printable Version
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On KCBS Radio today - teejers1 - 11-25-2020
they were interviewing a doctor from UCSF (epidemiologist I think) and the topic was quarantining people. When asked if he thought the 14 day quarantine was warranted, he said "no." He further said he did not know where that number came from, and that he was fine with a 7-day quarantine (he specifically said "I think seven is sufficient" when asked if lowering the quarantine period to 7-10 days made sense), provided there was a negative test at the end of that 7-day period. And he furhter said the 14 days came a while back before we knew that much about the virus. And this commentary was in connection with general quarantine protocols, not those with college athletes (who are testing every day).
I tried to post this in the thread where I wondered if the 14 day conference quarantine rule would be lessened, but couldn't find that thread.
Regardless, I found the commentary interesting. I know someone here said 14 days is the potential transmission period after exposure, but this doctor did not agree with that.
The interview also touched upon vaccine distribution and the UCSF doctor said 3 Bay Area hospitals would be recipients of the initial doses. I looked for the interview on the KCBS site but could not find it. But I did find a lead story on the vaccination story.
Some signs of hope . . .
https://sanfrancisco.cbslocal.com/video/4906554-covid-some-bay-area-hospitals-plan-for-early-distribution-of-pfizer-vaccine/
RE: On KCBS Radio today - Goose - 11-25-2020
(11-25-2020, 08:22 PM)teejers1 Wrote: I know someone here said 14 days is the potential transmission period after exposure, but this doctor did not agree with that.I am almost positive that the 14 day period is the maximum incubation period that is expected for COVID-19. It could take that long after exposure for you to develop enough viral load to transmit the disease and to test positive. I am also almost positive this limit has been observed in real life. In fact, a few incubation periods around 20 days have been reported.
It is a probability function. Probably most people who are exposed and are actually going to get the disease will test positive by day 7, but not all. How much is "most" vs "all"? I don't know. If it is 99% of the population then ending the quarantine at 7 days and a negative test makes sense. If it is 80% then it probably does not. By now, these numbers should be known. Show us the graph of the cumulative density function and then we can have an intelligent discussion about this topic. Otherwise, it is all BS.
I just hope they aren't reducing the number knowing it is not a good idea but hoping that people will comply with 7 because they haven't and won't with 14.
RE: On KCBS Radio today - teejers1 - 11-25-2020
(11-25-2020, 09:38 PM)Goose Wrote:(11-25-2020, 08:22 PM)teejers1 Wrote: I know someone here said 14 days is the potential transmission period after exposure, but this doctor did not agree with that.I am almost positive that the 14 day period is the maximum incubation period that is expected for COVID-19. It could take that long after exposure for you to develop enough viral load to transmit the disease and to test positive. I am also almost positive this limit has been observed in real life. In fact, a few incubation periods around 20 days have been reported.
It is a probability function. Probably most people who are exposed and are actually going to get the disease will test positive by day 7, but not all. How much is "most" vs "all"? I don't know. If it is 99% of the population then ending the quarantine at 7 days and a negative test makes sense. If it is 80% then it probably does not. By now, these numbers should be known. Show us the graph of the cumulative density function and then we can have an intelligent discussion about this topic. Otherwise, it is all BS.
I just hope they aren't reducing the number knowing it is not a good idea but hoping that people will comply with 7 because they haven't and won't with 14.
So I did a little more Googling and found this from UCSF. It's a travel guide that mentions the 7 days with a test. Perhaps that is what was being discussed when I caught the interview. It still looks like Option A is 7 days and then if you feel good and test negative on Day 7 you can return to work; Option B is 14 days quarantine, if you feel good you can return to work (w/o a test). Is either an option only if you don't think you've been exposed; and 14 days is required if you've been exposed?
Maybe. But I'm still not sure why you'd have a 7-day option for travel return if you're worried about unknown exposures, from asymptomatic carriers or otherwise.
https://coronavirus.ucsf.edu/travel
Maybe I'm misinterpreting things . . . certainly possible.
RE: On KCBS Radio today - Goose - 11-25-2020
(11-25-2020, 10:02 PM)teejers1 Wrote:OK, I understand. The problem is different if you don't know if you have been exposed. The statistics for a random person are undoubtedly different and probably not nearly so useful. Even as bad as things are, a random person probably isn't going to start shedding virus in any given 7 day window, or 14 day window for that matter. They "probably" aren't sick and won't be. In Taiwan, they just assume that all travelers have been exposed and proceed from there. That is a conservative approach, and many may say it is overkill. However, it is unclear to me that any other approach is really viable. UCSF might have some rationale for saying if you aren't positive in 7 days you aren't going to be, but I can't imagine what it is. It would be nice if they told us.(11-25-2020, 09:38 PM)Goose Wrote:(11-25-2020, 08:22 PM)teejers1 Wrote: I know someone here said 14 days is the potential transmission period after exposure, but this doctor did not agree with that.I am almost positive that the 14 day period is the maximum incubation period that is expected for COVID-19. It could take that long after exposure for you to develop enough viral load to transmit the disease and to test positive. I am also almost positive this limit has been observed in real life. In fact, a few incubation periods around 20 days have been reported.
It is a probability function. Probably most people who are exposed and are actually going to get the disease will test positive by day 7, but not all. How much is "most" vs "all"? I don't know. If it is 99% of the population then ending the quarantine at 7 days and a negative test makes sense. If it is 80% then it probably does not. By now, these numbers should be known. Show us the graph of the cumulative density function and then we can have an intelligent discussion about this topic. Otherwise, it is all BS.
I just hope they aren't reducing the number knowing it is not a good idea but hoping that people will comply with 7 because they haven't and won't with 14.
So I did a little more Googling and found this from UCSF. It's a travel guide that mentions the 7 days with a test. Perhaps that is what was being discussed when I caught the interview. It still looks like Option A is 7 days and then if you feel good and test negative on Day 7 you can return to work; Option B is 14 days quarantine, if you feel good you can return to work (w/o a test). Is either an option only if you don't think you've been exposed; and 14 days is required if you've been exposed?
Maybe. But I'm still not sure why you'd have a 7-day option for travel return if you're worried about unknown exposures, from asymptomatic carriers or otherwise.
https://coronavirus.ucsf.edu/travel
Maybe I'm misinterpreting things . . . certainly possible.
RE: On KCBS Radio today - fullmetal - 11-26-2020
I am near certain 14 days is related to the drop-off in observed viral genomic load in patients. Whether patients are actively shedding viral particles or not toward the end of that period has not been ascertained afaik, but that length of time is related to how long researchers have been able to detect the viral genome via PCR.
One hypothesized source of the ASU football covid outbreak was Halloween parties, which would have been a 12-day incubation period. Another hypothesized source of the outbreak (perhaps more likely) was partying by non-travel team players during their Nov. 7th game vs. USC in Los Angeles, which would put the incubation period at 5 days. I suppose the latter is more likely, but if the former is true, then we do have to exercise an abundance of caution. And I think these are antigen tests, not merely the day of reported symptoms, as this outbreak was detected during the course of daily Pac-12 football covid testing. (How long does it take to produce antigens from date of infection...? Eh...)
RE: On KCBS Radio today - chrisk - 11-26-2020
The reason for these discussions now is the report that the CDC is considering a reduction in its recommended 14-day quarantine. Ideally, it will provide its rationale if it changes its recommendation.
RE: On KCBS Radio today - Goose - 11-26-2020
(11-26-2020, 02:36 AM)chrisk Wrote: The reason for these discussions now is the report that the CDC is considering a reduction in its recommended 14-day quarantine. Ideally, it will provide its rationale if it changes its recommendation.I think you are correct, and I really think it is imperative they provide their rationale. By now, with all the cases we have and the tracking and tracing that we do have (imperfect as it may be), we should have an excellent measure of what percentage of people who are exposed to COVID-19 first test positive on day N, for N in 1..14. That data will tell the story. If day 7..14 add up to 0.1%, 7 is fine. If it is 10%, 7 probably isn't fine. In between, we can argue. If, OTOH, the CDC just changes the guidelines and provides no data, something is rotten in Denmark.
RE: On KCBS Radio today - BostonCard - 11-26-2020
If you look at figure 2 in this paper, it provides the cumulative distribution function of the incubation period.
Based on the figure, the median incubation period is 7 days (table 2 estimates it at between 5 and 7 days). Depending on the model, the 95th percentile (that is, 95% of the time, the incubation period is that length or shorter) is 10 - 13 days depending on which model is chosen. The 99th percentile 12 to 18 days, again depending a bit on the model.
Here's a review paper that finds something similar.
Quote:Results The incubation period distribution may be modelled with a lognormal distribution with pooled mu and sigma parameters (95% CIs) of 1.63 (95% CI 1.51 to 1.75) and 0.50 (95% CI 0.46 to 0.55), respectively. The corresponding mean (95% CIs) was 5.8 (95% CI 5.0 to 6.7) days. It should be noted that uncertainty increases towards the tail of the distribution: the pooled parameter estimates (95% CIs) resulted in a median incubation period of 5.1 (95% CI 4.5 to 5.8) days, whereas the 95th percentile was 11.7 (95% CI 9.7 to 14.2) days.
So, reducing the quarantine period would increase the risk that someone on the tail end of the distribution makes it through. However, assuming the more optimistic model is correct, you can probably reduce the quarantine period to 10 - 12 days and still be able to catch about 95% of secondary cases. If you add asymptomatic testing at the end, you will probably catch some asymptomatic and pre-symptomatic secondary cases that may not have become symptomatic until the tail end of the distribution.
On that basis, I think a 10-day quarantine period with testing at the end probably is supported. A seven day quarantine period is probably too short.
BC
RE: On KCBS Radio today - teejers1 - 11-26-2020
(11-26-2020, 02:36 AM)chrisk Wrote: The reason for these discussions now is the report that the CDC is considering a reduction in its recommended 14-day quarantine. Ideally, it will provide its rationale if it changes its recommendation.
I just raised the point because I heard the interview. And both that interview and the UCSF travel recommendation are set - i.e., completed before any action the CDC may or may not take.
RE: On KCBS Radio today - Goose - 11-26-2020
(11-26-2020, 12:49 PM)BostonCard Wrote: If you look at figure 2 in this paper, it provides the cumulative distribution function of the incubation period.
Based on the figure, the median incubation period is 7 days (table 2 estimates it at between 5 and 7 days). Depending on the model, the 95th percentile (that is, 95% of the time, the incubation period is that length or shorter) is 10 - 13 days depending on which model is chosen. The 99th percentile 12 to 18 days, again depending a bit on the model.
Here's a review paper that finds something similar.
Quote:Results The incubation period distribution may be modelled with a lognormal distribution with pooled mu and sigma parameters (95% CIs) of 1.63 (95% CI 1.51 to 1.75) and 0.50 (95% CI 0.46 to 0.55), respectively. The corresponding mean (95% CIs) was 5.8 (95% CI 5.0 to 6.7) days. It should be noted that uncertainty increases towards the tail of the distribution: the pooled parameter estimates (95% CIs) resulted in a median incubation period of 5.1 (95% CI 4.5 to 5.8) days, whereas the 95th percentile was 11.7 (95% CI 9.7 to 14.2) days.
So, reducing the quarantine period would increase the risk that someone on the tail end of the distribution makes it through. However, assuming the more optimistic model is correct, you can probably reduce the quarantine period to 10 - 12 days and still be able to catch about 95% of secondary cases. If you add asymptomatic testing at the end, you will probably catch some asymptomatic and pre-symptomatic secondary cases that may not have become symptomatic until the tail end of the distribution.
On that basis, I think a 10-day quarantine period with testing at the end probably is supported. A seven day quarantine period is probably too short.
BC
Once again we have to thank BC for providing the information. I would point out that a reduction to 10 day quarantine relies on the more optimistic study results and also on the idea asymptomatic testing at the end would reduce the 10 day rate to 95%. I guess it also requires the minimum target goal to be 95%. We really don't have the data to say that this testing would accomplish that, so if it were me, I would say 12 days. YMMV. There are two important points to be made here, IMHO. First, 7 days clearly is too short. Second, whatever the CDC changes it's recommendations to be (if indeed it does so), it needs to provide an equivalent analysis to what BC has provided here. If they do not, I will be very disappointed and very suspicious. It can be done, we see it here. Not doing so would be malfeasance on the part of the CDC.