Since the generation time of a virus is very difficult to estimate, most studies rely on the serial interval which is estimated from the interval between clinical onsets. Given that most analysis use the serial interval, it is paramount to have an estimate of the precise onset dates of the symptoms.

I did a analysis for all states in Brazil using data from SIVEP-Gripe, the complete analysis is available here.

In the image above, we can see the gamma mean estimate for the delay on each state in Brazil. Below you can see the distribution for Rio Grande do Sul / RS: