Most of Brazil is pretty temperate year-round, so they don't really have a very sharp flu season, but what they do have typically peaks around June, which fits with when the covid drop started.

https://en.wikipedia.org/wiki/Flu_season#Timing -> https://academic.oup.com/aje/article/165/12/1434/125289

> In the Fourier analysis, the seasonality of influenza in Brazil was characterized by a semiannual pattern, peaking in the winter month of June (amplitude = 27 percent), with a second, smaller peak during the summer (January; amplitude = 13 percent; figure 2).