Peru is reeling from record case counts of dengue fever. What's driving the outbreak?

LIMA, Peru – For Lorena Vigo, getting dengue, the virus once known as "breakbone fever," was like no illness she had previously experienced.

On top of the headache, upset stomach and aching joints, she bled from her gums after coming down last month with the mosquito-borne virus in Piura. That's the city of 600,000 residents in northern Peru that is the epicenter of the Andean nation's record-breaking dengue outbreak.

"There were no beds at the hospital," says the 43-year-old, explaining how she was unable to use the public health insurance that she pays into monthly as the health-care system was overwhelmed by the epidemic.

"Everyone I knew got it. At the hospital pharmacy [where her insurance would be accepted], the queue was so long that I didn't even bother to line up. I ended up paying for my own medicines and just treated myself at home."

So far this year, nearly 150,000 Peruvians have come down with the disease, according to the Pan American Health Organization. The current death toll is 248 in what is by far Latin America's most intense dengue outbreak.

A rising tide of dengue

The Andean nation is not alone. The disease is on the rise around the globe. The World Health Organization says reported cases jumped from 505,430 in 2000 to 5.2 million in 2019. Most cases are asymptomatic or result in only mild sickness. But a number of patients do go on to develop severe dengue, which can be fatal in up to 13% of untreated patients, according to the Centers for Disease Control.

There is no cure. Treatment of the symptoms revolves around keeping patients hydrated and administering paracetamol, but not some other painkillers, which can actually make the patient worse. Recovery typically takes about a week.

One vaccine is in development but not yet approved in Peru. Another vaccine has proven problematic, leading to a greater chance of developing severe dengue among those not previously infected.

Peru's unprecedented outbreak has been driven by unusually warm and rainy conditions on Peru's desert coast, first triggered by Yaku, a tropical cyclone not normally seen in this part of the Pacific, and then a localized "coastal" El Niño effect of warmer ocean waters. Both hit in April and May.

That has allowed the Aedes aegypti mosquito, which spreads the four viruses that cause dengue, to breed in large numbers, leaving larvae anywhere there are just a few millimeters of standing clean water.

A report by the Rockefeller Foundation notes that the Aedes mosquito can now "overwinter in more regions," thanks to rising temperatures — which also "enhance dengue virus replication" within the insect, speed up the growth of larvae and cause adult mosquitoes to "bite more frequently."

The unusual weather in Peru is expected to continue, and even intensify and spread to other parts of South America, as the global El Niño weather phenomenon is predicted to gather force later this year.

Poverty is also contributing to the outbreak, with nearly one in 10 Peruvians lacking running water and one in four without sewerage. Many rely on fleets of unregulated water trucks and then store the liquid at home in unsealed containers where mosquitoes can breed, further turbocharging the outbreak.

Harsh words for the government response

Dr. Leslie Soto, an infectious diseases expert and spokesman for the Medical Association of Peru, is one of many who have criticized the government's handling of the epidemic even though it was widely predicted.

"There's been a lack of preparation," he said. "We knew this El Niño was coming. We knew that we needed to get ready yet we didn't. Managing dengue is not the same in a region where it's not prevalent, and where the population doesn't know what precautions to take – like not leaving anything that could be a receptacle for water – as in an area like the Amazon where it is endemic."

He said that the outbreak was exacerbated by a public health-care system widely viewed as shambolic and under-resourced in a country that had the world's highest COVID-19 mortality — 665 deaths per 100,000 population.

"Above all, we need to improve our primary care," he said. "People don't trust it after COVID." In this dengue outbreak, he noted, those who fall ill often bypassed local clinics and went straight to hospitals, which should only be treating the most serious cases. "We don't have the staff, the infrastructure or the medicines," Soto added.

Rosa Gutiérrez, who was forced to resign as health minister on June 16, was widely viewed, both by medical experts and ordinary Peruvians, as out of her depth in handling the outbreak.

To widespread incredulity, she insisted in May that the outbreak would be "resolved" in two weeks, a claim that she was subsequently forced to apologize for. She was also heavily criticized for using dengue statistics that were two weeks out of date during a trip to Piura in an apparent attempt to downplay the severity of the situation, claiming that there were 5,350 cases and one fatality in the region of Piura, of which the city of Piura is the capital. At the time she was speaking, on May 30, the region had more than 42,000 infections and 39 dead.

"But it's not just the health ministry," says Soto. "It's also the education ministry, the housing ministry, infrastructure and regional governments," which are failing. One of the many problems he criticized was the lack of potable water and sanitation services at schools, with pupils often forced to wash their hands in plastic tubs and flush toilets with buckets of water, making the schools dengue hot spots and forcing the Piura regional government to close them for several weeks.

Government measures to address the outbreak have included fumigation, and warning residents to use mosquito nets at night and avoid leaving out anything that could become a receptacle for rainwater, from rubber boots to dishes for potted plants.

What scientists say about the outbreak

Scientists are reluctant to finger climate change as the culprit for this outbreak. But the combination of this year's Yaku, the coastal El Niño and Peru's unusual weather have created conditions that let the mosquitoes that spread the disease thrive.

Strong global El Niños, like the one predicted to take effect later in 2023, typically hail warmer global averages the following year, warns Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, one of the world's leading climate change research centers. That means that 2024 could potentially be the hottest year on record.

It might even mean that it could be the first year that mean global temperatures exceed preindustrial averages by more than 1.5° Celsius, the limit set by the United Nations as necessary to avoid devastating climate change.

"I don't think we will pass it [1.5° in 2024]," Schmidt told NPR. "But we will get uncomfortably close."

The current dengue outbreak could offer a window into what's going to be an ever more common occurrence as global warming continues.

And there are clear signs that dengue is no longer confined to the Global South. In the past decade or so, cases have been reported for the first time in countries including Canada, Croatia and France.

Simeon Tegel is a British journalist based in Lima, Peru, from where he regularly roams across Latin America. He covers most topics under the sun, from human rights and democracy to cuisine and travel but specializes in environmental stories. A regular contributor to the Washington Post, he has also published stories in The Independent, The Times, The Telegraph, USA Today, Foreign Policy, Vice, the Spectator and, in Spanish, El País. A foodie and an outdoorsman, he is as at home dining in Lima's finest restaurants as he is bivvying out on a glacier 17,000 feet above sea level or bushwacking through the Amazon.

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