system
Given the following post, respond as if you're commenting on Reddit:
human
How has COVID changed the way we study virus transmission?

When the COVID pandemic first started, there were a host of countermeasures that we now think of as unnecessary, such as sanitizing groceries.  It seems that scientists have learned a lot about how COVID is  transmitted since the beginning of the pandemic. Did we really not understand how viruses are transmitted? Was it just this virus? Do all viruses have different transmission mechanisms? How has the science of virus transmission study evolved since 2018?
gpt
We actually understood a lot about how viruses are transmitted at the time.

Those countermeasures we now think unnecessary at the time we’re necessary. Ineffective but necessary. 
Covid was a new disease killing a lot of people. We didn’t have enough knowledge about it so it was safer to overestimate safety measures. Like if we took every countermeasure for every kind of virus, then we know it’s airborne, so we take a step back to only those effective to airborne viruses. We dropped countermeasures as we discovered more about that specific virus behavior, but in general it’s within what we already knew about transmission.