Only 9% of Brazil's COVID-19 cases are asymptomatic, study shows
RIO DE JANEIRO (Reuters) - Less than 10% of people infected with the novel coronavirus in Brazil were asymptomatic and the majority of those who tested positive for the COVID-19 respiratory disease had mild symptoms, a survey of almost 90,000 people from all regions showed on Thursday.
According to the epidemiological research funded by Brazil's Health Ministry and carried out by the Federal University of Pelotas in the southern state of Rio Grande do Sul, people who tested positive for the virus showed five main symptoms: fever, cough, alteration of smell/taste, body pain and headache.
A total of 2,064 of 89,387 people surveyed between May 14 and June 24 in three phases tested positive for antibodies, of whom 91% showed symptoms of COVID-19.
"The literature has become accustomed to saying that most patients are asymptomatic. Our study suggests that most patients have mild symptoms, but are not asymptomatic," Pedro Hallal, professor at the Federal University of Pelotas and coordinator of the research, said at a news conference.
The research also showed the pace of transmission slowing over the course of the three phases of the study. After growing 53% from late May to early June, the transmission rate slowed to 23% from early June to the end of the same month, Hallal said.
The survey also corroborates some experts' claims that the outbreak in Brazil is much larger than the official figures suggest, with the difference between the number of confirmed cases and the percentage of the population with antibodies as much as six times in the areas surveyed.
Hallal warned, however, that it cannot be said that the pandemic is six times greater than the almost 1.5 million cases officially confirmed in Brazil, since the study is limited to 133 cities.
"It is normal to have more people with antibodies than the confirmed cases, but whether it is exactly eight or six or 10 times depends on the dynamics of the other 5,000 cities that were not included in the survey," he said.
(Reporting by Pedro Fonseca; Writing by Gabriela Mello; Editing by Leslie Adler)
