Nine months into this it would be nice if we had good data on the risk factors of transmission. I know it’s a tricky virus to trace but shouldn’t we have better info on which activities demographics, etc are the most risky by now?
We do know the risk factors. It's a respiratory disease that spreads when people who are breathing are near each other. We don't need a random control trial to tell us that practicing with your brass band can spread it. The solution is to stay very far from everyone until the disease is wiped out. Only very intelligent libertarian contrary Americans think we don't have the information we need.
That is not very helpful advice when you have to manage risk while trying to eat, work, live, and stay healthy. Stats certainly exist on where some of the 16,000+ cases in San Mateo were transmitted.
There's no way to get the information you desire without Big Brother level tracing. And even then the error bars are huge. Symptoms set in days after exposure, and transmission is uneven at best.
Full disclosure: I've had covid.
We assume we were exposed at the clinic, where our kid needed emergency medical treatment. But if so, only one of us was with the child indoors -- in a cleaned room with a doctor in full PPE and us in masks -- and treatment lasted less than 5 minutes.
But by the time we experienced onset of symptoms, days later, we had been in close proximity with my in-laws (they need care and were part of our bubble) for over 24 hours. Luckily, they developed no symptoms and tested negative.
So 5 minutes of exposure to an asymptomatic carrier at the clinic likely transmitted the virus to us, but 24 hours in close contact failed to transmit the virus to my in-laws.
The delay of onset and inconsistent transmission patterns make this virus exceedingly difficult and expensive to track. Your questions are unanswerable.