Viral load decline

May 30, 2022 8:01 AM

If you have used rapid tests to guage your infectiousness at the end of a bout of covid, did you get fainter positives before testing negative?

I'm day 7 since my day 0 symptoms/first positive rapid test, and my rapid test is still turning positive pretty much immediately, line visible within 2 minutes and very solid by the end of the test.

I'm not sure how long it takes for the viral load to drop off once it starts to decrease. Does anyone go from a solid positive one day to a negative test 24 hours later, or am I almost certainly in for at least a day or 2 of faintly positive tests before I can expect a negative?

I am aware that rapid tests may or may not perfectly match to infectiousness, and I am aware that there's a wide range of recovery times.

I am not making any isolation choices based on the self-reported results of other people's rapid tests.

Thanks!

posted by the primroses were over to Health & Fitness (10 answers total)

Here is my rapid test journey from this month’s Covid infection, my first. I’m fully vaxxed with one booster:

Day 1: completely negative
Day 2: instantly brightly positive
Day 8: faint positive
Day 10: squint and you see the line positive
Day 13: negative

Days 3-7 I didn’t test because I felt terrible and there was no point.

Everyone’s path to recovery is different though. You know this, I know this, but this is AskMe and I’ll get it out of the way before you have 5 people swoop in and tell you that.
posted by kimberussell at 8:15 AM on May 30, 2022 [11 favorites]

Yes - when I first tested it was instant and dark red, over the next week or so it took longer to show up and faded to a light pink.
posted by Laura_J at 8:54 AM on May 30, 2022 [2 favorites]

For what anecdata is worth: Everyone I am aware of who has tracked with daily or near-daily home tests has experienced fainter results for at least a day or two before a full negative. That's probably ten or so people at this point whose testing regimens I'm actively aware of and up to date with. None of them went from a quick full dark response to a negative response.
posted by Stacey at 8:57 AM on May 30, 2022 [6 favorites]

Anecdotally, I kept my solid/quick red line right up until day 8 or 9, and then it slowly started to fade. I wasn't showing negative until 14 days or so. (FWIW, I also was slow to show positive at first -- I felt sick for at least 24 hours before testing positive.)
posted by BlahLaLa at 9:41 AM on May 30, 2022 [2 favorites]

My partner’s tests showed fading lines over the course of several days, then negative/no line on Day 13, then a faint but still firmly present line on Day 14, before finally testing negative several days in a row from Day 15 onward.
posted by CtrlAltDelete at 10:56 AM on May 30, 2022 [3 favorites]

I have two (both vaccinated & boosted, different households) friends who each had the exact same progression - feel sick for 1-2 days but test negative, test faint positive, test strong positive for several days, test faint positive, back to negative. I don’t recall the exact timing, but I know both were frustrated that they still had clear positives around the one week mark.
posted by maleficent at 11:18 AM on May 30, 2022 [2 favorites]

I took a rapid test every day while I had COVID (mainly for my own scientific curiosity).

My timeline:

• For the first 5 days I got very solid positives which appeared instantly.
• Day 6 was the first day the line was slightly fainter, and took a couple seconds to develop rather than showing up instantly.
• Day 8 was my first negative test (when read at 15 minutes -- a faint line did appear after about 30 minutes).
• Day 9 was a true, definite negative.

FWIW, in terms of symptoms, I was very sick for the first 2-3 days, but feeling mostly back to normal by around day 5.
posted by mekily at 12:47 PM on May 30, 2022 [3 favorites]

You may want to read this thread I had two days ago and the NYT article I found on the end on this topic. Around 20-25% of people keep testing positive for around up to 12 days or so(?) afterwards and they sound like they don't agree as to whether or not you're still infectious despite your test results.

Studies suggest that while most people stop testing positive on antigen tests sometime during the first 10 days of their illnesses, a notable subset of people continue to test positive for longer, for reasons that scientists do not entirely understand.
In some cases, these people may still be shedding infectious virus, but in others, the tests may be picking up viral debris from a waning infection, experts say, making it difficult to know how to interpret the results.
“Some people may not be infectious at the end of their course even if still antigen-positive, whereas others may be infectious even if antigen-negative,” said Dr. Yonatan Grad, an immunologist and infectious disease expert at the Harvard T.H. Chan School of Public Health.
Given the uncertainty, some experts have advised that test results at the end of an infection be viewed as just one potentially useful piece of information considered in concert with other factors, including a patient’s symptoms and immune status. Along those lines, Dr. Chin-Hong recommended “using the rapid test as a guide but not the be-all and end-all.”
According to a new analysis of people who sought repeat testing at a California site during the Omicron wave, an estimated 71 percent were antigen-positive four days after their symptoms appeared or after they first tested positive for the virus. That percentage declined over the following days, but an estimated 20 percent were still positive on Day 11, according to the study, which has not yet been published in a scientific journal.
In the other study, which enrolled vaccinated students and staff at Boston University, researchers found that while most participants no longer had positive viral cultures six days after their symptoms began, a small number had viable virus as late as Day 12.
“You can be somewhat reassured by a negative test, but the positive test is not particularly helpful,” said Dr. Tara Bouton, an infectious disease specialist at the Boston University School of Medicine and an author of the study.
Dr. Barczak’s team found that some people tested antigen-positive slightly beyond the point of having positive viral cultures. This suggests that at the end of an infection, there may be a brief period during which the tests are simply detecting lingering bits of viral protein. The study was not large enough to draw conclusions about how common this would be or how long the effect might last, she said.

Anecdata from Saturday: the person who tested positive on day 10 showed me pictures of his tests from Saturday morning (day 11) and then Saturday afternoon and they were fainter and fainter--the last one was barely seeable. Someone else I talked to the next day said they had similar results.
posted by jenfullmoon at 2:55 PM on May 30, 2022 [2 favorites]

I suspect you’ve got enough replies here already, but yup — Day 1 was a faint positive that within hours started to test as nearly black! By Day 10 it had become fainter than the control line, and Day 12 I started getting some (but not all) come back negative. Within a couple of days, no T line on any test.

Whether this equates to contagiousness, as others have noted, opinions differ. You must be safer once the line has gone though. But it’s not necessarily live, dangerous virus being found by the end.
posted by breakfast burrito at 5:42 PM on May 30, 2022 [1 favorite]

Response by poster: Thanks to everyone for their anecdata! My covid afflicted acquaintances have mostly followed the time isolation guidelines, so little comparison points on later test results.

FWIW, my sample line took longer to show up on later tests before disappearing, but never got faint. When I got negatives on days 9 and 10, finally, I spent a long time peering at them in various lights trying to discern a faint positive, but there was none to be seen.
posted by the primroses were over at 8:48 AM on June 2, 2022