A question for Po (probably). I continued to produce faint lines of positive for about four or five days. They would have been something like days 6,7,8,9 on the app which would correspond with something like 9,10,11,12 after the onset of symptoms.
Would I simply be shedding dead virus, or would there still be the possibility that I might be contagious even at that late stage? I suppose the question really is “can an LFT differentiate between live and dead virus?” Or, as usual, is it more complicated than that?
Sorry to hear that you got some rough time and glad that you are getting better now. From what I heard in the recent weeks, a longer positive period is more common. I doubt that it's because the test getting better, but that the virus load is generally higher in the case of Omicron.
For your question, yes, it is possible that LFT can also pick up inactive viruses, albeit it is a different principle of testing compared to PCR. PCR detects viral RNA and LFT detects viral protein. Note that LFT is less sensitive than PCR, so if you can see signal in LFT, then there is quite some viral protein to be detected, which means there are still many virus particles.
The US CDC
"The likelihood of recovering replication-competent (infectious) virus is very low after 10 days from onset of symptoms, except in people who have severe COVID-19 or who are moderately or severely immunocompromised.
- For patients with mild COVID-19 who are not moderately or severely immunocompromised, replication-competent virus has not been recovered after 10 days following symptom onset for most patients.(38,39,54-58) With the recommended shorter isolation period for asymptomatic and mildly ill people with COVID-19, it is critical that people continue to properly wear well-fitted masks and take additional precautions for 5 days after leaving isolation.(59,60) Modeling data suggest that close to one-third of people remain infectious after day 5 and can potentially transmit the virus.(61) Outliers exist; in one case report, an adult with mild illness provided specimens that yielded replication-competent virus for up to 18 days after symptom onset.(62) ..."
However, all those papers cited were from 2020 or early 2021, when there was no even delta strain data, let alone Omicron. As said it was less known that people would have more than 9 days positive in LFT, but nowadays I heard more people having more than 9 days of LFT positive.
I think for a balanced approach, if you want to protect other people, which is a responsible and gracious thing to do (there is no more legal requirement for you to isolate anyway), maybe be extra careful when you still tested positive in LFT, avoid face to face contact without wearing a good facemask, especially if you still have some symptoms such as coughing.