What's the latest information on COVID exposure-to-contagious timeline?
August 15, 2024 11:18 AM Subscribe
If person A is exposed on Day 0 and tests positive on day 4, when would person A likely become contagious and when would person B, who was exposed to person A on Days 1-4, likely become contagious? If the information is available on the CDC website I couldn't find it, and I don't know what sites are trustworthy anymore...everything the CDC has related to that seems to be archived.
Also, is the guidance still to test daily for 5 days after exposure? Does it make a difference if the person is high risk?
Also, is the guidance still to test daily for 5 days after exposure? Does it make a difference if the person is high risk?
Response by poster: Clarification: person A didn’t know they were exposed, so didn’t test until day 4. So I assume they were contagious day 3 or earlier.
posted by lemonade at 12:00 PM on August 15
posted by lemonade at 12:00 PM on August 15
Regarding daily testing, there is no particular downside except annoyance and cost. If cost is not a factor there is nothing stopping you from testing even 2X daily.
The advantage of more frequent testing is that, if you do end up getting a positive test, you are likely to get it sooner.
If you are planning antivirals such as paxlovid, starting it sooner definitely helps - starting one day sooner could make a difference. I don't know that it would a h-u-g-e difference but probably a noticeable difference.
The other thing you can do in advance is get your paxlovid (or whatever) plan in place. Some doctors will even write paxlovid prescription in advance and maybe you could even fill it in advance. But either way you could at least talk to your doctor, get any medical issues discussed (with paxlovid you have to stop some medications for a while, also people with reduced kidney function have a different dosage schedule, there can be other considerations). Ideally the instant you have a positive test you could call or message them & get the prescription going immediately
Most people could get a paxlovid prescription instantly via a telemedicine appointment or maybe even at the pharmacist. BUT, didn't apply if you happen to have complex medical issues such as kidney disease or liver disease (it looks like this might have changed now if you have the needed lab results/medical records you can show them - but if you have reduced kidney or liver function many pharmacists may not be comfortable). Again, something to work out in advance if you can.
There is also a network of "test to treat" providers that might be helpful.
posted by flug at 12:10 PM on August 15
The advantage of more frequent testing is that, if you do end up getting a positive test, you are likely to get it sooner.
If you are planning antivirals such as paxlovid, starting it sooner definitely helps - starting one day sooner could make a difference. I don't know that it would a h-u-g-e difference but probably a noticeable difference.
The other thing you can do in advance is get your paxlovid (or whatever) plan in place. Some doctors will even write paxlovid prescription in advance and maybe you could even fill it in advance. But either way you could at least talk to your doctor, get any medical issues discussed (with paxlovid you have to stop some medications for a while, also people with reduced kidney function have a different dosage schedule, there can be other considerations). Ideally the instant you have a positive test you could call or message them & get the prescription going immediately
Most people could get a paxlovid prescription instantly via a telemedicine appointment or maybe even at the pharmacist. BUT, didn't apply if you happen to have complex medical issues such as kidney disease or liver disease (it looks like this might have changed now if you have the needed lab results/medical records you can show them - but if you have reduced kidney or liver function many pharmacists may not be comfortable). Again, something to work out in advance if you can.
There is also a network of "test to treat" providers that might be helpful.
posted by flug at 12:10 PM on August 15
Best answer: The Public Health Agency of Canada has an explainer for health professionals that was updated in 2024 and is clearer than anything I could find on the CDC website:
For testing, FDA's testing regime recommends up to 3 tests, each 48 hours apart. If someone's symptomatic and high risk, I think it makes sense to test more frequently.
posted by toastedcheese at 12:25 PM on August 15 [5 favorites]
"The time period in which an individual with COVID-19 is infectious remains uncertain. A person may be infectious for up to 3 days before showing symptoms (pre-symptomatic infectiousness).So the answer is basically *shrug emoji*, but masking and avoiding crowds for two weeks seems courteous.
"Viral RNA levels appear to be highest just before or soon after symptom onset."
"The incubation period ranges from 1 to 14 days. The median is 5 to 6 days between exposure and symptom onset. Most people (97.5%) develop symptoms within 11.5 days of exposure."
For testing, FDA's testing regime recommends up to 3 tests, each 48 hours apart. If someone's symptomatic and high risk, I think it makes sense to test more frequently.
posted by toastedcheese at 12:25 PM on August 15 [5 favorites]
Clarification -- you are asking specifically for SARS-COV2 here? These timelines are different for other infectious agents.
posted by gingerbeer at 3:39 PM on August 15 [1 favorite]
posted by gingerbeer at 3:39 PM on August 15 [1 favorite]
Based on the tags, yes, I'm assuming covid. And yeah, the answer is currently still kind of "shrug emoji" on the timelines for infectiousness and when a test might be positive. I would test for more than five days after a known exposure, myself, but then I am in a household with multiple higher-risk people so we aim above and beyond the current CDC guidelines.
If you have a trusted primary care doctor, it might be worth a call to get recommendations that take A and B's specific health history and conditions into account, and to line up paxlovid or other recommended treatments/symptom relief in case it's needed.
posted by Stacey at 5:21 PM on August 15
If you have a trusted primary care doctor, it might be worth a call to get recommendations that take A and B's specific health history and conditions into account, and to line up paxlovid or other recommended treatments/symptom relief in case it's needed.
posted by Stacey at 5:21 PM on August 15
Response by poster: Oops yes COVID, been a lot going on around here..... Thank you all for the information and suggestions!
posted by lemonade at 7:07 PM on August 15
posted by lemonade at 7:07 PM on August 15
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This does vary somewhat by strain, but I think it would be surprising to test positive before day 2 or even day 3 after a day-zero exposure. If I had one specific confirmed exposure, I probably wouldn't bother testing til day 2, but there's no real harm in doing it earlier, just jamming ten bucks up your nose.
posted by praemunire at 11:31 AM on August 15