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The new coronavirus was already circulating in Brazil in the first week of February, even before the first case was confirmed from abroad, estimates a survey led by the Oswaldo Cruz Institute of the Oswaldo Cruz Foundation (IOC / Fiocruz). According to the study, community transmission of the virus began around February 4, at least 20 days before the first case was diagnosed in a traveler who arrived from Italy on February 26.
The investigation indicates that the circulation of Sars-CoV-2 already occurred in Brazil almost 40 days before community transmission was confirmed in São Paulo and Rio de Janeiro, on March 13. As the arrival of the virus precedes community transmission, the data indicates that its introduction in Brazil took place in late January.
The researchers also analyzed international data, and their methodology confirmed other studies that point to the start of community transmission in Europe between mid-January and early February. In New York, the epicenter of covid-19 in the United States, community broadcast would have started in early February. In all cases, virus circulation began two to four weeks before confirmations of the first case in travelers.
The study was published in the scientific journal Memórias do Instituto Oswaldo Cruz and included the participation of the AIDS and Molecular Immunology Laboratory of the IOC / Fiocruz, Fiocruz-Bahía, Federal University of Espírito Santo (UFES) and Universidad de la República (Udelar) In uruguay. In view of the urgency of scientific information on the disease, the publication took place in the quick access section dedicated to pandemic studies. The full text is available here.
According to the study, finding the beginning of community transmission through genetic analysis is hampered by the short time that has elapsed since the start of the epidemic and the limited number of Sars-CoV-2 genomes that have already been sequenced in most of the countries.
The researchers then developed a statistical method to estimate the start of community transmission from the number of deaths in the first few weeks. The total number of deaths is considered the most reliable data, due to the lack of evidence and the large number of asymptomatic cases. Based on these data, the scientists considered that the average time between infection and death is three weeks and that the mortality rate is around 1%.
To confirm the validity of the method, the calculation was applied to cases in the United States and China, where there was already a certain date for the start of community transmission based on the genetic analysis of Sars-CoV-2. The results obtained with the statistical calculation were similar to those of the genetic analysis.
The IOC notes that the investigation corroborates other evidence that the coronavirus began to circulate in Brazil before the first officially confirmed case.
One of them is the hospitalization of patients with severe acute respiratory syndrome (SARS), measured by the Infogripe system of Fiocruz. The number of hospitalizations is higher than that observed in 2019 since mid-February.
SOURCE: Agência Brasil
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