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Comment by nikolay | Hacker News Reader

I don't get this - if you're symptomatic beyond day 9, how can you not be contagious? A dry cough, for example, should be caused by the virus still being alive in the upper respiratory tract, i.e. you still should be able to infect others. Did they test aerosols, too?

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What you feel as symptoms are your immune responses, you can not "feel" the actual virus. The immune reponse should go on for longer than the virus is functional.

Also, there has to be above a certain viral load to be contagious. I am however far from qualified to even guess what the thresholds are and I would think that it is mostly a matter of definition.

Coughing is a taxing activity - it wastes energy, and causes discomfort. We cough for a reason - I doubt it's from the solidarity to infect others. Of course we can sense the virus, but the irritation it causes. Do all viruses, which replicate in the nasopharyngeal tract, trigger coughs? Maybe some viruses evolve to cause irritation similar to air passage obstruction, which triggers the instrict to clear your throat up?

Our bodies are not perfect or omniscient. We cough because it is evolutionarilly favored as a way to dislodge irritants, and viruses are evolutionarily favored to cause that coughing response strongly in order to spread. Coughing too long seems like a very possible consequence of those.

The irritation still persists from the damaged tissue after the virus is eliminated. It takes time to rebuild.

So, senescent cells are just left for days to build up damage? We have mechanisms to clear up dead cells, many of them which actually killed themselves via apoptosis and were not directly killed by the virus.

Live virus doesn't really cause symptoms as such, although they evolve to take advantage of it. The virus is basically re-purposing then melting a bunch of cells. The body's immune response is killing the viral structures and turning whole areas into the cellular equivalent of a battleground, killing off anything that is or is likely to be controlled by the virus.

Many of the worst symptoms aren't related to the presence or absence of the virus itself. If someone is turning blue from lack of oxygen, it isn't that the virus is doing anything here and now. It is that their lungs are non-functional from damage that the virus already did (note: past tense). You could remove every trace of active coronavirus from them and while they'd probably not get worse they also wouldn't get better very quickly. New lungs don't grow overnight.

This is not true. Viruses can directly kill the cells, by interfering with biological processes, necessary for cellular survival.

The clarification is helpful, but everything said was in fact true. Omitting this clarification doesn't negate everything else they said.

What the poster said above is incorrect. Covid does produce damage directly to the lung and neural cells, which especially evident as loss of smell and taste. The severe, deadly reaction is indeed of the immune system.

That's what I saw in many explainer videos, too.

Are also the loss of smell and messed up taste effects of the immune system? I caught Covid at the end of October, and those symptoms lasted well beyond the final negative molecular swab test, so it seems the case.

PCR tests for RNA fragments. After 9 days it's likely you are surveying the battle field remains not actual live virus.

Naive guess: the damage was already done. Cough is a response to the damage caused by the virus, not to the virus itself.

If you get shot, you still have a bullet wound when the bullet comes out.

Damaged cells are cleaned up pretty fast. Of course, it's the virus causing damage, but we cough for the purpose to clear up the passages. In addition, the respiratory viruses probably trigger the cough as a vehicle to spread to other people.

> A dry cough, for example, should be caused by the virus still being alive in the upper respiratory tract

Why? I thought the body’s (potentially delayed) reaction caused the cough, not the virus

We have the instinct to cough to clear our air passages even without pathogens in certain cases. The virus is triggering these thru some irritation in order to spread to other people.

Right, but whatever process causes the coughing could well outlive the virus itself

Bother to provide any proof?

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