Scientists have analysed the spread of Covid-19 among people in Manaus, Brazil, where more than 70 per cent of the population used to be infected inside seven months of the novel coronavirus arriving in the city, findings which shed light on what may happen whether the disease spreads unmitigated.
Brazil has experienced one of the most world’s most hastily growing Covid-19 epidemics, with the Amazon being the worst hit region, according to the researchers, including those from Harvard University in the United States.
They said in Manaus, the largest metropolis in the Amazon, the first SARS-CoV-2 case used to be reported in mid-March, after which non-pharmaceutical interventions (NPIs), such as social distancing, were introduced.
This used to be followed by an “explosive” epidemic associated with moderately high mortality, and then by a sustained drop in new cases despite relaxation of NPIs, the study, published in the publication Science, famous.
To explore if the epidemic used to be contained because infection reached the herd immunity threshold, or on account of other factors such as behavioural changes and NPIs, the scientists collected data from blood donors in Manaus.
They inferred the virus attack rate from the collected blood samples, and compared this data with that of Sao Paulo, which used to be less impacted.
The researchers estimated a 76 per cent attack rate in Manus by October, including adjustments for waning antibody immunity.
By comparison, the attack rate in Sao Paulo by October used to be 29 per cent, partly explained by the larger population size, they added.
Despite the tremendous toll the virus took in these two cities, the scientists said the attack rates remain lower than predicted in a mixed population with no mitigation strategies.
“It is likely that NPIs worked in tandem with growing population immunity to contain the epidemic,” they famous, also acknowledging voluntary behavioural changes as helping.
Alternatively, the scientists imagine further studies in the region are “urgently” needed to decide the longevity of population immunity.
“Monitoring of new cases…may also be imperative to understand the extent to which population immunity might prevent future transmission, and the potential need for booster vaccinations to bolster protective immunity,” they wrote in the study.
(This story has been published from a wire agency feed without modifications to the text.)
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