oh it is here
https://www.cdc.gov/sars/about/faq.html#lab
the antibody test is as above
PCR -
https://en.wikipedia.org/wiki/Polymerase_chain_reaction
get them to spit
the virus will be present and so its DNA will be as well
very small copies of DNA can be made very large in quantity by PCR ( cycles ) - read it and get 5 copies ( cycle one) read them and get 5 copies now 25, and another cycle ( 125) repeat up to 20 times - 5 to the power 20
and thenshoot it up a gel column with a control
if present it will level-peg the control bar
and if neg then it will not show anything next the control bar