
Why the US still doesn’t have a contact tracing app for Covid-19 - asgardanalytics
https://www.philippcannons.com/2020/04/11/why-the-us-still-doesnt-have-a-contact-tracing-app-for-covid-19/
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streetcat1
I might be missing something, but I fail to see how contact tracing is useful,
due to secondary contacts/infections.

I.e. contact tracing is like a BFS search on a graph.

So, even if you trace the closest contacts, by the time a person takes the
test and notify the network, those primary contacts (edge 0) might have
infected their own contacts (edge 1) until basically you would need to isolate
the whole population.

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pdkl95
Contact tracking is probably useful at the _beginning_ of a new outbreak when
the disease is still isolated to a small number of locations. Isolating a few
people might prevent the disease from spreading to other areas.

As you described, once an outbreak has a foothold in most areas, most people
will be within one or two hops from someone who is infected. Also, the
potential useful period will be shorter when the incubation period is long.
Two weeks of incubation provides a _lot_ of opportunity for someone to spread
the infection.

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nunez
No app that you can optionally download from the App Store would work. It
would require a critical mass for it to be effective, and we don't have the
kind of time required for this to happen. This is probably why Apple and
Google are working on it together.

