The corona virus began circulating in Brazil in the first week of February, more than 20 days before the first case was diagnosed during Carnival. A study by Fiocruz’s Instituto Oswaldo Cruz concluded this using a methodology based on death records by Covid-19.
The first case of the disease was identified on February 25, in a traveler returning from Italy to Sao Paulo. On March 13, the first official confirmation of community transmission occurred, when it was no longer possible to trace the origin of the virus.
To investigate an outbreak, it is ideal to find viral genomes found in patient samples. However, this methodology cannot be applied because of the short time since the start of the pandemic and the limited number of available genomes.
Thus, the researchers developed a new method, using death records to identify the start of transmission, as a “delayed” tracker. This is because the average time between infection and death by Covid-19 is about three weeks.
Translated by Kiratiana Freelon
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