  The severe acute respiratory syndrome of coronavirus 2 spread globally very
quickly, causing great concern at the international level due to the severity
of the associated respiratory disease, the so-called COVID-19. Considering Rio
de Janeiro city (Brazil) as an example, the first diagnosis of this disease
occurred in March 2020, but the exact moment when the local spread of the virus
started is uncertain as the Brazilian epidemiological surveillance system was
not widely prepared to detect suspected cases of COVID-19 at that time.
Improvements in this surveillance system occurred over the pandemic, but due to
the complex nature of the disease transmission process, specifying the exact
moment of emergence of new community contagion outbreaks is a complicated task.
This work aims to propose a general methodology to determine possible start
dates for the multiple community outbreaks of COVID-19, using for this purpose
a parametric statistical approach that combines surveillance data, nonlinear
regression, and information criteria to obtain a statistical model capable of
describing the multiple waves of contagion observed. The dynamics of COVID-19
in the city of Rio de Janeiro is taken as a case study, and the results suggest
that the original strain of the virus was already circulating in Rio de Janeiro
city as early as late February 2020, probably being massively disseminated in
the population during the carnival festivities.
