Cases of dengue fever surge across Brazil
Infectious disease experts warn of global risks
BRASÍLIA — Patients lying motionless in the waiting room, moaning for help. Desperate hunts for an open hospital bed. Emergency room arguments over medication.
Not since the darkest days of the COVID-19 pandemic, when hospital systems all over this country ruptured under the weight of the disease, has Brazil witnessed such scenes.But this time, it’s dengue fever that has led states all over the country to declare a state of emergency and even spurred the construction of a field hospital in the nation’s capital of Brasília.
The disease is ripping through much of South America, where scientists say rising temperatures due to climate change have both extended the territorial range of the mosquito that carries dengue and increased its proliferation.
In the first two months of this year, Paraguay registered nearly 100,000 suspected cases, more than five times the typical rate. Peru, wracked by its own outbreak, has declared an emergency in much of the country. Argentina, too, has seen an explosion of cases.
But the disease has surged with particular virulence in Brazil, where epidemiologists expect the number of dengue cases to reach into the millions — more than doubling the previous record — and potentially kill thousands of people.
The deepening public health crisis, epidemiologists say, serves as a warning to the world. The struggle against the disease has entered an unpredictable, perilous new phase. Dengue is now creeping into places where it has never been in recorded time. And where it has long been, case numbers are soaring to unseen heights.
Many who are infected never develop symptoms, but others get a high fever, headaches, body aches, nausea, and a rash. While most get better after a week or so, some develop a severe form that requires hospitalization and can be fatal.
The disease has historically been confined to tropical climates. But in recent years, as cases have skyrocketed across much of the world — rising eightfold since the turn of the millennium — the virus has increasingly spilled over into areas once largely spared.
Local transmission is now being reported in America’s warmer, wetter states, where the disease’s vector, the Aedes aegypti mosquito, already roams. Florida last year reported a record 178 cases of local transmission. California, Arizona, and Texas are also detecting local transmission. The same dynamic is also being seen in Southern Europe, where dozens of cases of local transmission were recorded last year.
Epidemiologists warn this is probably only the beginning. In the coming years, as climate change broadens the reach of the A. aegypti mosquito, the disease could become increasingly prevalent, even endemic, across much of Southern Europe and the southern United States.
“It’s becoming a public health crisis and coming to places that have never had it before,” said Gabriela Paz-Bailey, who specializes in dengue at the Centers for Disease Control and Prevention.
The risk in wealthier northern climes is attenuated by several factors, including the prevalence of screened windows, widespread air conditioning, and strong sanitation practices, which can shrink the number of pools of stagnant water, where the mosquito can breed.
But epidemiologists say the threat should not be dismissed, especially not this year. Brazil registered more than 1 million cases of dengue fever in January and February alone.
By the end of the year, the country is expected to suffer 4.2 million.
“There hasn’t been extensive transmission in the United States, but that may change,” said Albert Ko, an epidemiologist at Yale University. “We should be concerned that a large epidemic season in Brazil and the rest of South America will drive spread and transmission to places in the US.”
For years, cases of dengue in Brazil have steadily risen. They jumped from a few hundred thousand per year in the early 2000s to more than 1.4 million in 2013, then again to nearly 1.7 million last year. But this year, several forces combined to unleash an outbreak without precedent.
An extraordinary heat wave collided with El Niño, which often coincides with greater dispersion of dengue, leading to wider proliferation of the A. aegypti mosquito and elongating its lifespan.
“It’s not just how many there are, but that they live longer,” said Kleber Luz, who coordinates research of A. aegypti-transmitted diseases at the Brazilian Society of Epidemiology. “Even if it’s just one or two days, this will affect the number of dengue cases.”
Then came another accelerant: the simultaneous circulation of all four types of dengue fever. That reduced immunological protections people might have otherwise had in a country where dengue has long been present. “I’ve been working with dengue since 1997,” Luz said, “and I’ve never seen another year when all four are circulating at the same time.”
Felipe Naveca, an epidemiologist with the Oswaldo Cruz Foundation, a Brazilian scientific research institution, said moments such as this one, when multiple dengue variants are circulating, are particularly perilous, because people can catch the disease multiple times over a short period. Cases will probably remain high as each variant peaks in succession.
“The scenario isn’t good,” he said.