In reply to stevieb:
> I don’t know if it’s the same test kit, but one kit was claiming it could detect between 3-33 days after infection.
Wow, so much that is misleading and unclear in that Guardian article. Not surprised you are confused.
They consistently mix up two completely different tests. The one available now is a highly sensitive test detecting viral RNA by converting it to DNA and amplifying it (an RTqPCR TaqMan assay). This should detect virus very early in the infection (theoretically it might detect a single molecule of viral RNA). I don’t know how long it takes for the virus to be cleared completely but I can imagine that it might be negative a few weeks after clinical signs have disappeared (assuming there’s no remaining latent virus - not likely in this case).
The second test is an ‘antigen’ / ‘antibody’ / serological test. This detects circulating specific antibodies against viral proteins. For a primary infection (where the person has never seen this particular virus) antibodies gradually rise over a couple of weeks and peak after about a month. They then decline if there’s no further challenge but might still be detectable for some months with a good test.
Actually, for viral infections like this, a better measure might be antigen-specific CD8+ T cells, but I digress.
I think it’s this second test that the fuss about but don’t worry, because Chris Whitty made it very clear that, despite what Matt Hancock said, there was no way the general public would have access to serological tests any time soon.
Post edited at 20:21