Brazilian health officials hunt mosquitoes in fight against dengue outbreak

A small team of state public health workers slalomed through auto parts strewn across Rio de Janeiro's junkyards, looking for standing water where mosquitoes might be laying eggs.

The moves were part of a nationwide effort to curb a surge in the country's mosquito-borne dengue fever during the country's key tourist season, which runs until the end of February.

Entomologist Paulo César Gómez, 56, discovered several mosquito larvae swimming in shallow rainwater inside the bumper of his car.

“We call these types of locations strategic points,” he said, because they have a high turnover rate because products come from all over the place. “It's hard not to have mosquitoes here.”

Earlier this month, just days before the start of Rio's world-famous Carnival, the city, along with several states and capitals, announced a public health outbreak following higher-than-normal numbers of dengue cases this year. declared.

“The number of infections in January was higher than in any other January,” Ethel Maciel, head of health surveillance at Brazil's Ministry of Health, said in an interview with The Associated Press.

Brazil has recorded 512,000 confirmed and probable cases so far this year, almost four times as many as the same period last year.

So far this year, 425 dengue deaths are under investigation and 75 have been confirmed, but the total for 2023 is just over 1,000.

Dengue fever is a viral infection that is transmitted to humans through the bite of an infected mosquito. Frequent rains and high temperatures facilitate the hatching of mosquito eggs and the development of larvae, making the notoriously hot city of Rio particularly susceptible to outbreaks.

According to the World Health Organization, many people who are infected do not develop symptoms, but dengue fever can cause high fever, headache, body aches, nausea, and a rash. In most cases, he recovers within a week, but in some cases, the condition becomes severe enough to require hospitalization and even death.

Wearing masks and plastic gloves, medical workers like Gomez comb through junkyards on hot mornings, gently kicking and shaking piles of car parts that can spread dengue fever. I looked for traces of the sexual Aedes aegypti mosquito.

Every time Gomez saw standing water, she took a hand pipette from her bag and searched for larvae, which she collected in a white plastic container. The captured mosquitoes and larvae are transported alive to a city laboratory where they are tested for dengue fever.

In areas with positive tests, health personnel will spray the walls with a mosquito-killing product and monitor the area for several weeks.

The Health Ministry's Maciel said the first warning of a possible outbreak was issued in September.

Brazil's leading research institute, the state-funded Oswaldo Cruz Foundation (Fiocruz), has published several studies showing that the number of infected people in Brazil could rise from 1.6 million in 2023 to up to 4.2 million this year. A scenario was formulated.

Maciel said the spike is due to excessive heat and heavy rain, both of which are part of climate change and El Niño, a natural, temporary, and occasional warming of parts of the Pacific that changes weather patterns across the planet. He said there was a possibility of an impact.

Maciel also noted that four dengue virus serotypes were circulating at the same time, including one that authorities had not identified for 15 years.

Health officials say more than 80% of Rio's mosquito breeding grounds are in residential areas. Efforts to fight dengue should therefore start at home, and raising awareness is important, said Rio de Janeiro state health surveillance authority Mario Sergio Ribeiro.

State officials launched a “10 Minutes to Save Lives” initiative, encouraging residents to check their homes, offices and places of worship for standing water.

Medical workers and volunteers went door-to-door and criss-crossed the narrow streets of Rio's working-class favela, or Tabajara, to spread the word. They handed out leaflets and climbed onto rooftops to search for rainwater containers.

One elderly woman, Birza da Costa, told The Associated Press that she believed she had contracted the disease.

“It started with a fever, itching all over my body, weakness and a lot of pain. It was really bad,” she said. “There are a lot of mosquitoes here.”

Health workers welcomed visitors with free repellent during Carnival, which ended on Wednesday. Vans carrying giant mosquito crosses and the words “No Dengue Every Day” opened and closed the parade over several nights, watched by millions of television viewers.

Maciel said the impact of Carnival won't be known for another week. Although dengue fever is not contagious from person to person, increased numbers of tourists may accelerate the spread of the disease to previously unaffected areas.

Maciel said it is unclear whether the number of infections has peaked and will start to decline, or whether the worst-case scenario is actually occurring.