Can someone explain the antibody test for Covid? I understand basically what it means to have antibodies but how does one have a false positive? Don’t they look for specific antibodies? Either you have them or not? I am sorry is this has been explained. TIA.
Antibodies are very small. The test needs to be quite specific. In about 1-2% of tests, the results are invalid (usually on the side of missing antibodies, but there are other, similar antibodies to prior SARS-COV-1.
I'm not sure what people expect of science, particularly sophisticated tests involved in antibody testing or in virus testing. 100% is super-rare in science. Gravity is held to be 100% active on Earth. Not much else is certain.
Many things effect why these 1-2% result errors happen. Some people's antibodies fall below the level of detection (and they probably shouldn't count themselves as having antibodies against CoVid anyway - so it seems to me, that's not a worthless test result at all).
Another reason for a false negative would be that the individual in question has rare genes for antibody formation, and hence, didn't form the same antibodies (there are many aspects to how an immune system works, it's not all antibodies - what if some people possess such great immune systems that CoVid was suppressed in some other way? How would we even know at this point?)
Anyway, anything that's 98-99% accurate as a test is pret' darned good, IMO. CoVid-19 testing, especially at the beginning of the pandemic in the US, weren't even that accurate - but lots of study done since. And the upcoming saliva tests may be less sensitive, but much less invasive and therefore suitable for use in children, which is important.
Things are going to fall through the cracks. That's why anti-viral campaigns need redundancy (and the nations with multiple anti-CoVid systems in place are doing very well in eradicating it and suppressing it).
I wonder if we'll ever get to where we have a national quarantine on incoming travelers.
WHO guidance: Healthy people should wear masks only when ‘taking care of’ coronavirus patients
This is why people are confused: The WHO says healthy people should wear masks only when taking care of Coronavirus patients: this is clearly at odds with CDC guidelines.
The way I see it, a mask is a barrier- so if someone sneezes or coughs, their droplets stay in the mask--- so what is the harm in wearing it? If someone is asymptomatic, even breathing on someone for a protracted period of time can spread the virus.
i think the WHO is giving bad advice and i just don't understand it.
WHO is not known as your "State of the Art" advice place. Our own CDC, fearing a mask shortage, said similar things. But it does a good job coordinating data collection efforts in poorer countries, and has been instrumental in getting basic care advice to Africa in particular, but also many places in Asia and Latin America.
I suspect the US will continue to use their data whenever relevant (as it's important) but simply not pay for membership.