Why are Covid cases in ‘epicentre’ South America suddenly falling?

Experts are struggling to explain a sudden drop in Covid-19 infections in the region that until recently was the epicentre of the global pandemic.

As recently as last month, The Lancet reported that the South America accounted for almost a quarter of all Covid-19 deaths despite being home to just 5% of the world’s population.

Leaders in the region’s 12 sovereign states are now “breathing a sigh of relief” following a “sharp and fast” decline in infection rates, said The New York Times (NYT), but “experts can’t quite explain it”.

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‘Covid surge’

Just weeks ago, Covid was spreading with “alarming ease” across a cluster of South American nations, “overwhelming hospital systems and killing thousands of people daily”, said the NYT.

The Lancet reported that “strained and underfunded health systems, deep social inequalities and increasing poverty, slow vaccination rates and increased spread of new variants” were leading to a surge of Covid deaths, which had already topped a million across the region by mid May.

According to Statista, three of the ten countries in the world with the highest fatality tallies are in South America. Brazil is in second place, with almost 584,000 deaths to date, with only the US recording more. Peru is fifth, with more than 198,000 deaths, followed by Colombia in tenth place, at more than 125,000.

And experts believe that many coronavirus deaths in countries across the region have not been recorded in official tallies.

The South American nations of Paraguay, Suriname, Argentina, Uruguay, Colombia, Brazil and Peru have also suffered a “silent decimation by Covid unlike that anywhere else in the world”, said The Guardian.

Continental recovery

Against this backdrop, the sudden drop in infection rates has surprised experts, who note that “there have been no new sweeping or large-scale containment measures in the region”, said the NYT.

One possible “major factor” contributing to the drop may be “the speed with which the region ultimately managed to vaccinate people”, the paper suggested.

In Chile and Uruguay, more than 70% of the population has been fully vaccinated, according to Oxford University tracking. In Brazil, nearly 64% of the population has received at least one dose of a vaccine, as have 61% in Argentina, which has so far reported more than 112,000 deaths.

Experts have also suggested that many people have developed natural immunity after having had the virus. Jairo Mendez Rico, an adviser on emerging viral diseases at the Pan-American Health Organization, told the NYT that while the drop in cases is “not easy to explain”, the Delta variant of Covid may have been slow to gain traction in South America because populations hit herd immunity.

However, he cautioned that natural immunity could leave the continent vulnerable to new variants - a potential danger that threatens to reverse South American’s gains.

New threats

The emergence of one variant in particular is already giving experts cause for concern.

First identified in Peru and now spreading across South America, the Lambda strain is highly infectious and more resistant to vaccines than the original version of Covid that emerged from the Chinese city of Wuhan, according to Japanese researchers.

In lab experiments, scientists found that three mutations in Lambda’s spike protein help it resist neutralisation by vaccine-induced antibodies.

The strain has “largely slid under the radar for the past nine months”, said National Geographic, in part because it was frequently mistaken for the Gamma variant that first emerged in Brazil.

But Lambda “likely caused the high number of infections during the second wave between the end of March and April”, according to the magazine, and is “gaining ground” across South America.

Public complacency also poses a danger. The NYT notes that “as cases have dropped, schools in much of the region have resumed in-person classes”, while “airports are becoming busier as more people have started travelling for work and leisure”.

President Alberto Fernandez of Argentina said in late July that a return to pre-Covid life was fast approaching. “We deserve another life, a life in which we enjoy music, painting, sculptures, movies, theatre,” he said. “A life in which we can laugh without a face mask, where we can hug those we love.”

But Chrystina Barros, a health care expert at the Federal University of Rio de Janeiro, told the paper: “There is a serious risk of putting the very effectiveness of the vaccine at risk. The cooling of the pandemic cannot inspire people to relax in relation to the crisis.”