Hacker News Reader

Comment by tdrdt | Hacker News Reader

Note that this means a PCR-test will have no meaning other than you came in contact with Covid-19 somewhere between now and up to 3 months ago.

The PCR-test measures the existence of virus RNA. Not when you were infected, if you are sick of that virus and also not if you are contagious.

Because the symptoms are now similar to almost all other virus infections there is no way of knowing if you are sick of Omicron after a positive PCR-test.

Edit: For some confused people an example. You came in contact with Omicron but didn't get sick of it. 2 weeks later you came in contact with the RS virus and this time you got a runny nose so you get a PCR-test. The result is positive from the Omicron contact 2 weeks earlier. So they say you are sick of Omicron. But in fact you are sick of RS.

View on HN

> there is no way of knowing if you are sick of Omicron after a positive PCR-test.

Huh? I though Omicron was particularly obvious on a PCR test (spike-negative but virus-positive).

Indeed, it can very easily be identified due to some gene deletion.

I am not saying the PCR-tests are false. See my added example.

Not all Covid PCR tests target the S-gene. The cheap RT-PCR test I took recently in London (for travel) targeted only the E-gene and ORF1ab sequences, so if it had been positive it wouldn't have told me if it were Omicron or not.

With previous waves you were likely to become PCR negative around 2-3 weeks after initial infection, though it was longer for some people. We don't have data for omicron yet on this.

As for whether you have omicron - that depends on the precise test the lab runs. Many UK labs test for three covid genes - S, N and Orf. Delta was S-gene positive. Omicron is S-gene negative but N and Orf positive. If the test is S-gene negative (often reported as S-gene target failure, SGTF), you can be pretty sure it's Omicron at the moment. Alpha was also SGTF, but isn't really circulating anymore.

What? PCRs are by far the best proxy we have for active infection. And no, people don't typically (ever?) test positives anywhere near 3 months after.

Common symptoms being less specific doesn't make PCRs unreliable.

I am not saying the PCR-test are unreliable. See my added example.

It's still contrived.

> asymptomatic people may test positive for 1-2 weeks, while those with mild-to moderate disease often continue to test positive for a week or more after this.

Per https://www.gavi.org/vaccineswork/false-negative-how-long-do...

Three weeks is a stretch in an asymptomatic case, let alone three months.

Reply on news.ycombinator.com