HomeLatest ThreadsGreatest ThreadsForums & GroupsMy SubscriptionsMy Posts
DU Home » Latest Threads » Forums & Groups » Main » General Discussion (Forum) » How long after exposure b...

Fri Jul 31, 2020, 11:32 AM

How long after exposure before you will test positive? What say you Harvard Medical School?

Harvard Medical School - If you've been exposed to the virus

*snip*
What are the chances that a coronavirus test will tell me I am not infected when I actually am?

The chances that a coronavirus test will give you a false negative (indicating that you are not infected when you actually are infected) depend upon the type of test you have and when in the course of your infection the test is performed. There are two main types of tests:

nasal/throat swab tests and saliva tests, both of which detect the virus itself
blood tests that detect antibodies that your immune system produces in response to the infection.
If you get the nasal/throat swab or saliva test, you will get a false negative test result:

100% of the time on the day you are exposed to the virus. (There are so few viral particles in your nose or saliva so soon after infection that the test cannot detect them.)
About 40% of the time if you are tested four days after exposure to the virus.
About 20% of the time if you develop symptoms and are tested three days after those symptoms started.

This possibility of a false negative test result is why anyone who has symptoms that could be due to COVID-19, or has been exposed to someone known to be infected, must isolate even if they test negative for coronavirus.

The blood antibody test does not become positive (or might never be positive in some people) until many days after exposure, and is therefore not the primary test used for diagnosis. It is very useful for research and public health decision making.

*snip*

So, is Barr self-isolating? Asking for a friend.

14 replies, 1533 views

Reply to this thread

Back to top Alert abuse

Always highlight: 10 newest replies | Replies posted after I mark a forum
Replies to this discussion thread

Response to lettucebe (Original post)

Fri Jul 31, 2020, 11:39 AM

1. A friends wife has been sick and self isolating

I guess she has tested negative twice but the docs say her symptoms are so classic they are sure she has it. I donít know how much time elapsed from when she stated feeling it and got tested. Or the second test. She hasnít been severely ill yet; dry caugh, no sense of taste and smell is all Iíve heard of.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 11:43 AM

2. Absolutely, and if and when a vaccine is released to the public, social distancing and masks need to

still be adhered to.

It is highly unlikely that any vaccine will be 100% effective, and until the level of sars co v2 is down to low levels, and herd immunity is established, it would be prudent to continue following social distancing and masks



Reply to this post

Back to top Alert abuse Link here Permalink


Response to still_one (Reply #2)

Fri Jul 31, 2020, 11:50 AM

5. Given there are other infectious disease such as the flu

I was sort of thinking I might wear a mask in public from now on. I'm not a big fan of being sick and I can't be the only father of small kids that has noticed the much healthier lifestyle social distancing, washing hands, and masks has brought to our house

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Johonny (Reply #5)

Fri Jul 31, 2020, 11:54 AM

8. That too. Excellent point

Reply to this post

Back to top Alert abuse Link here Permalink


Response to still_one (Reply #2)

Fri Jul 31, 2020, 11:53 AM

7. What about the anti-vaccers?

Reply to this post

Back to top Alert abuse Link here Permalink


Response to demosincebirth (Reply #7)

Fri Jul 31, 2020, 11:55 AM

9. I would like to think that the anti-vaccers are not a significant portion of society, but I don't kn

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 11:45 AM

3. So all this trump bs about people being tested is basically bullshit


because the quick test is the blood one

Seems there really is no reliable test for it until too late in the game.

which applies to those fever checks, too.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 11:45 AM

4. I keep hearing several days to two weeks is how long the incubation period is.

So, those people trying to claim well Herman Cain was tested right after the rally are full of it. He wouldn't have tested positive yet. The incubation period would have been longer. So, those "after" tests they keep claiming at the Tulsa rally were a waste of time and really show how ignorant everyone in Trump's campaign really are. It also shows just how ignorant at least all of his supporters who were present and who are using that as some excuse to defend him, really are too. But, then, we already knew that.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 11:50 AM

6. So, it seems that

You shouldn't even bother getting tested until at least three days after you have actual symptoms. (At which point you probably feel too ill to go get tested.) Otherwise, just keep self-isolating if you think you may have been exposed in any way (which is every time you go to the grocery I guess). This is pretty much what we've been doing anyway.

This was sort of the protocol at the beginning of the pandemic, when only symptomatic people were told to get tested. Are we going in circles?

ON EDIT: It seems that people really shouldn't get tested until symptoms, because otherwise a false negative will lead to a false sense of security and possible spread.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 12:18 PM

10. Does it say anywhere how long before contagious? Thinking if 4 days at 40% yet contagious

at two or three days, ... But, it may be that contagious is not until well after tested positive. Something I have not seen anywhere. Do we know?

Reply to this post

Back to top Alert abuse Link here Permalink


Response to LizBeth (Reply #10)

Fri Jul 31, 2020, 01:07 PM

12. 2 days prior to symptoms through illness

That is the period one is contagious.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Evergreen Emerald (Reply #12)

Fri Jul 31, 2020, 02:45 PM

13. That two or more days matter, before comes positive, and two days prior to symptoms is interesting.

Thanks much for the information. I didn't want to hunt and read

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 12:55 PM

11. K&R

Reply to this post

Back to top Alert abuse Link here Permalink


Response to lettucebe (Original post)

Fri Jul 31, 2020, 10:14 PM

14. K & R

Reply to this post

Back to top Alert abuse Link here Permalink

Reply to this thread