Study of virus attack rate in Manaus, Brazil, shows outcome of mostly unmitigated epidemic

December 08, 2020

Researchers studying data from blood donors in Manaus, Brazil, who experienced high mortality from SARS-CoV-2, estimate that more than 70% of the population was infected approximately seven months after the virus first arrived in the city. "Manaus represents a 'sentinel' population, giving us a data-based indication of what may happen if SARS-CoV-2 is allowed to spread largely unmitigated," write Lewis Buss and colleagues. Brazil has experienced one of the world's most rapidly growing COVID-19 epidemics, with the Amazon being the worst hit region. In Manaus, the capital and largest metropolis in the Amazon, the first SARS-CoV-2 case was reported in mid-March, after which non-pharmaceutical interventions (NPIs) were introduced. This was followed by an "explosive" epidemic associated with relatively high mortality, and then by a sustained drop in new cases despite relaxation of NPIs. To explore whether the epidemic was contained because infection reached the herd immunity threshold or because of other factors such as behavioral changes and NPIs, Lewis Buss et al. collected data from blood donors in Manaus - which they used to infer a virus attack rate - and compared it to data from blood donors from São Paulo, which was less impacted. Analyzing antibody positivity using SARS-CoV-2 IgG tests, the authors estimate a 76% attack rate by October. This estimate includes adjustments for waning antibody immunity. By comparison, the attack rate in São Paulo by October was 29%, partly explained by the larger population size, Buss and colleagues note. The authors say that, despite the tremendous toll the virus took in these two cities (where transmission is continuing today), 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 note, also acknowledging voluntary behavioral changes as helping. Further studies in the region are "urgently" needed to determine the longevity of population immunity, they say. "Monitoring of new cases ... will also be vital to understand the extent to which population immunity might prevent future transmission, and the potential need for booster vaccinations to bolster protective immunity."

American Association for the Advancement of Science

Related Virus Articles from Brightsurf:

Researchers develop virus live stream to study virus infection
Researchers from the Hubrecht Institute and Utrecht University developed an advanced technique that makes it possible to monitor a virus infection live.

Will the COVID-19 virus become endemic?
A new article in the journal Science by Columbia Mailman School researchers Jeffrey Shaman and Marta Galanti explores the potential for the COVID-19 virus to become endemic, a regular feature producing recurring outbreaks in humans.

Smart virus
HSE University researchers have found microRNA molecules that are potentially capable of repressing the replication of human coronaviruses, including SARS-CoV-2.

COVID-19 - The virus and the vasculature
In severe cases of COVID-19, the infection can lead to obstruction of the blood vessels in the lung, heart and kidneys.

Lab-made virus mimics COVID-19 virus
Researchers at Washington University School of Medicine in St. Louis have created a virus in the lab that infects cells and interacts with antibodies just like the COVID-19 virus, but lacks the ability to cause severe disease.

Virus prevalence associated with habitat
Levels of virus infection in lobsters seem to be related to habitat and other species, new studies of Caribbean marine protected areas have shown.

Herpes virus decoded
The genome of the herpes simplex virus 1 was decoded using new methods.

A new biosensor for the COVID-19 virus
A team of researchers from Empa, ETH Zurich and Zurich University Hospital has succeeded in developing a novel sensor for detecting the new coronavirus.

How at risk are you of getting a virus on an airplane?
New 'CALM' model on passenger movement developed using Frontera supercomputer.

Virus multiplication in 3D
Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies.

Read More: Virus News and Virus Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to