South America, Where Lambda and Mu Variants Broke Out, Sees COVID Cases Plummet

Almost every country in South America has seen a drop in new COVID-19 case numbers—with the situation marking a stark contrast to tallies seen just weeks ago.

The continent is where some of the COVID-19 variants of interest (VOIs) were first found, including the Lambda and Mu variants—which were first detected in Peru in December 2020 and Colombia in January 2021 respectively.

Lambda was later detected in other Latin American nations, including Argentina, Brazil, Chile, Colombia, Ecuador and Mexico.

But vaccination campaigns across the continent are picking up steam. There also appears to be lower vaccine hesitancy in Brazil and Mexico compared to the United States, according to a Morning Consult poll published this month.

Brazil, the continent's largest country, has suffered the second largest tally of COVID deaths in the world and was originally blighted by a slow vaccine rollout.

But now nearly 64 percent of the population has taken at least one dose of a vaccine, a rate that exceeds the U.S., according to data from Johns Hopkins University.

Data from the Our World In Data website shows Brazil saw a peak in case numbers on June 23, with its seven-day average of daily cases totaling 77,328. On September 6, this figure was at 21,093, nearly a quarter of that number.

Chile and Uruguay both have more than 70 percent of their populations fully vaccinated, while in Argentina more than 61 percent have had at least one dose.

Chile saw its seven-day average of daily cases drop from 7,294 on June 8, to 466 on September 5.

Uruguay saw its peak in cases on April 10 with 3925.14 cases as a seven-day average. On September 6, its seven-day average of new daily cases was 143.14. That same day, the country recorded no new deaths from the virus, down from a peak in April of 64 daily deaths linked to COVID.

Argentina saw its highest seven-day average of new daily cases on June 1, when it recorded 32,915. On September 6, this figure was 4,115.

Peru, where Lambda was first discovered, has seen its seven-day case average drop from its peak of 9,928 on April 13 to 845 on September 6. Its vaccination rate has been lagging behind some other South American countries, with only 33.4 percent of its population having had at least one dose of the vaccine.

Colombia saw a similar drop in cases, its seven-day average of daily cases peaked at 31, 256 on June 28. This figure was down to 1,787 on September 6. Nearly 48 percent of its population has had at least one dose of vaccine.

The infographic below, from Statista, shows the number of total confirmed COVID-19 cases in different South American countries as of September 3.

Statista chart COVID-19 cases South America
This infographic by Statista shows the countries with the number of COVID-19 cases in South American countries. Statista

Commenting on the this drop in cases across South America, Carla Domingues, an epidemiologist who ran Brazil's immunization program until 2019, told The New York Times: "Now the situation has cooled across South America. It's a phenomenon we don't know how to explain."

Jairo Méndez Rico, a viral diseases expert advising the World Health Organization, told the paper that the Delta variant may have been slow to gain traction in South America because there is already so much natural immunity in the region from people having contracted the virus.

Chrystina Barros, a health care expert at the Federal University of Rio de Janeiro, warned that countries in the region should not get complacent, despite lowering numbers.

"There is a serious risk of putting the very effectiveness of the vaccine at risk," she told The Times.

"The cooling of the pandemic cannot inspire people to relax in relation to the crisis."

Newsweek has contacted the World Health Organization (WHO) to ask for comment on this drastic fall in cases.

WHO and the Centers for Disease Control and Prevention (CDC) have three categories of COVID variants that make up their watch lists: variants of interest, variants of concern—which include alpha, beta, delta and gamma—and variants of high consequence.

The WHO officially labelled the mu variant a VOI on August 30.

In its weekly epidemiological update published on September 1, the WHO wrote: "The Mu variant has a constellation of mutations that indicate potential properties of immune escape."

The WHO noted that vaccinated individuals appear to show a "reduction in neutralization capacity" against mu and may have "potential properties" that are synonymous with the beta variant.

COVID-19 vaccine
A stock photo of a COVID-19 vaccine. Vaccine rollouts that have gathered steam have been credited as being one of the main reasons the virus has dropped drastically in South America. John Moore/Getty