^ Honest question, so don't get upset with me. What is the difference between testing positive for virus infection and positive for having developed the antibodies? If they have the antibodies, then that is a very conclusive test that they have had the virus and had an infection. If you're a carrier of the antibodies but asymptomatic, then you are recovered, right?

I can see companies being a lot more careful about encryption, data security, secure email, etc if more employees WFH, but there’s plenty of experience - e.g. IBM’s consultants have WFH for many years.

I’m interested in the air filtration thing. I figure most office buildings have shared air systems to some degree. Would a HEPA filter in your office, presuming you have an office instead of a cubicle, help if someone upstream in the HVAC system is coughing and sneezing SARS-COV-3?

A little bit of virus enters your body, enters your cells, multiplies. When it multiplies enough, you will test positive for the virus. Test positive for virus means a swab from wherever the virus is present (for this one, they stick long swabs down your throat) shows the “live” virus that is multiplying in your body. You’re infected, and you’re shedding virus so you’re contagious. You may be symptomatic or not.

After a delay, your immune system starts recognizing the virus as something foreign and starts fighting it. As part of this process, you create antibodies to the virus.

After you recover, the virus is no longer present in your body. You will test negative for the virus. You’re not infected anymore and not shedding virus thus not contagious.

However, the antibodies will remain in your body, ”on guard” as it were. If a little bit of virus enters your body, your immune system will attack it right away, not giving it a chance to get established and start multiplying. You’re immune. And you’ll test positive for antibodies, which usually involves taking a blood sample.

(Assuming you do actually become immune to this virus, which has been thought or hoped to be the case but is not really known).

Yes, if you test positive for antibodies but negative for virus, then you are a recovered case. Being asymptomatic doesn’t mean much, it seems 50% or more of people who are infected are asymptomatic.

^ Apologies in advance for going all Mahler on you guys.

But "test positive for the virus" how exactly? What are they detecting, if not the presence of antibodies? It's not like they smear blood plasma on a plate and hope to find .000000001 one actual tiny virus among all of the red blood cells. That would be ridiculously absurd.

The viral DNA or RNA is detected by the test usually by the ( fancy word warning!) reverse transcription polymerase chain reaction test.

Ah the ol' RTPCR test.

Overview of the different tests is here

https://www.scientificamerican.com/article/heres-how-coronavirus-tests-work-and-who-offers-them/

The technology of virus testing is indeed pretty impressive. The sample is swabbed from where the virus is most found, in this case the respiratory system. Then - well, read
https://www.emedicinehealth.com/pcr_polymerase_chain_reaction_test/article_em.htm#what_is_pcr_polymerase_chain_reacti on_used_for Something got a Nobel Prize for inventing this.

For antibody testing, here is an article https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30788-1/fulltext

Its maybe unappreciated that these tests are not simple, quick, or infallible. Often people think a task or service is easy and should be fast, cheap and perfect, while people actually doing the work are having to apply a bunch of judgment, steps, and technology to get something even sort of serviceable.

We’ve had a bunch of discussion about antibody studies, for example, with people going ape over is it 1% or 4% of the population, but most engaging in the discussion don’t seem to realize how fallible the tests used in the study are.

Common terms are sensitivity (what % of positive samples will be correctly reported as positive by the test) and specificity (what % of negative samples will be correctly reported as negative by the test).

For antibody tests, a given manufacturer’s test might be (typical example) 95% sensitivity and 97% specificity. That means 1 - 95% = 5% false negative (test 1,000 persons with antibodies, test will incorrectly report 50 lack antibodies) and 1 - 97% = 3% false positive (test 1,000 persons without antibodies, test will incorrectly report 30 have antibodies). So, if you get “3% of population has antibodies!”, are you seeing the truth or false positives?

I get them impression that the decision makers have a hard time getting their heads around this. https://www.cnn.com/2020/04/14/health/coronavirus-antibody-tests-scientists/index.html

yep, we used it a lot back in the 80's at J&J.