Thread by @firefoxx66

Why are scientists alarmed when the first #COVID19 cases we hear of in a country are deaths? I thought it worth clarifying.

It's not because we worry the virus is "bad", "getting worse" or "changing". It's because #SARSCoV2 *doesn't* seem to lead to death very quickly. (1/n)

It seems like #SARSCoV2 infection takes about 3-4 weeks to overwhelm someone & lead to death - if it does, which for many it does not.

But this then implies that when we see deaths, those people have had the virus for weeks beforehand... (2/n)

And if no cases or only very few, well-tracable cases were detected during those weeks, #SARSCoV2 was circulating undetected.

And then only detected in some people who got ill enough to die. We know that's only a small fraction of the population... (3/n)

So how many people are likely infected before you detect a death? Probably quite few. And with few or no cases, none of these people had reason to isolate or change their behaviour... So how many are infected now? (3/n)

We don't know the answer to these questions exactly, but we don't need to in order to appreciate that seeing deaths first, or at time of diagnosis, is concerning to scientists & public health.

It's a sign that #SARSCoV2 is circulating more widely than we thought. (4/n)

This then marks a change in strategy, as we've seen in Italy, where it's very hard to retrace & take action, sometimes impossible. These efforts are still worthwhile, but harder than when detect #COVID19 cases earlier in the chain.
(5/n)

Just as a general note since this has spread quite widely: I don't respond to trolls or conspiracy theorists - or insults.

I will try to respond to genuine questions if I can. However, lots of notifications: keeping up is hard. Also, work on #COVID19 still needs to be done!!

If you're rude to me in one reply & ask questions in another, I won't answer.
Continuing to be rude to me won't fix that, either.

And yes, 'rude' includes taking the tone that I'm an idiot. Be polite.

I'm also avoiding countering conspiracy stuff to not draw attention to it.