In Brazil's Amazon a COVID-19 resurgence dashes herd immunity hopes

Source: Reuters Published: 2020/9/28 20:38:40

The largest city in Brazil's Amazon has closed bars and river beaches to contain a fresh surge of coronavirus cases, a trend that may dash theories that Manaus was one of the world's first places to reach collective, or herd, immunity.

Satere Mawe indigenous men use a smartphone to contact a doctor in Sao Paulo State to receive medical guidance amid the novel coronavirus pandemic, at the Sahu-Ape community, 80 kilometers from Manaus, Amazonas State, Brazil, on May 5. Photo: AFP

When a large portion of a community becomes immune to a disease, its spread becomes unlikely.

University of Sao Paulo researchers suggested that a drastic fall in COVID-19 deaths in Manaus pointed to collective immunity at work, but they also believe that antibodies to the disease after infection may not last more than a few months. Local authorities on Friday enforced a 30-day ban on parties and other gatherings, and restricted restaurant and shopping hours, a setback for the city of 1.8 million.

In April and May, so many Manaus residents were dying from COVID-19 that its hospitals collapsed and cemeteries could not dig graves fast enough. Then in June, deaths unexpectedly plummeted. Public health experts wondered whether so many residents had caught the virus that it had run out of new people to infect. 

Research estimated that 44 percent to 66 percent of the Manaus population was infected between the peak in mid-May and August. 

The study by the University of Sao Paulo's Institute of Tropical Medicine tested newly donated banked blood for antibodies to the virus and used a mathematical model to estimate contagion levels. 

The high infection rate suggested that herd immunity led to the dramatic drop in cases and deaths, the study said.

Scientists estimate that up to 70 percent of the population may need to be protected against coronavirus to reach herd immunity.

In Manaus, daily burials and cremations fell from a peak of 277 on May 1 to just 45 in mid-September, the mayor's office said.
Newspaper headline: COVID-19 resurgence in Amazon dashes herd immunity hopes

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