Meg Norris was traveling in Argentina in April when the first signs of dengue struck her. The weather in Salta, just south of the Bolivian border, was warm, but Norris, a 33-year-old from Boulder, Colorado, pulled a fleece sweatshirt around her body to keep from shivering .
“I thought it was sun poisoning,” she said.
She woke up that night in a sweat and spent hours alternately burning and then freezing. In the morning, his eyes were sore and his lymph nodes were swollen. For the next week, there was nothing to do but sleep, stay hydrated, and wait for the aches and pains that give the disease the nickname “fracture fever” to go away.
Latin America is experiment its worst dengue outbreak on record. The number of cases in the first four and a half months of 2024 is already 238% higher than the same time last year, which itself ended with a record 4.1 million cases, according to Pan American Health Organization. Cases are more than 400% higher than the five-year average.
An unusually humid and hot summer season caused by the El Niño weather conditions has created ideal conditions for the mosquitoes that spread dengue fever to hatch en masse and carry larger quantities of the virus.
Experts warn this could be a preview of what dengue will look like in the future. Climate change creates unusually mild conditions, which are already expanding the range of mosquito-borne diseases.
“This is concerning for places where dengue has never appeared before in recent history: North America and Europe,” said Dr. Albert Ko, professor of microbial disease epidemiology at the Yale School of Public Health.
Dengue is a viral fever caused by four different viruses and transmitted by mosquito bites. It is common in many tropical regions of the world, but has begun to appear in more temperate climates. Dengue fever-carrying mosquitoes, Aedes aegypti, are now regularly found in the southern United States, but recently the insects have been found as far north as the Bay Area and Washington, DC One 2019. study predicts that 2 billion more people will be at risk of contracting dengue by 2080.
“We are really worried,” Ko said.
Why are dengue cases increasing around the world?
Dengue outbreaks historically occur in the Americas every three to four years, said Dr. Gabriela Paz-Bailey, chief of the dengue branch of the vector-borne disease division of the Centers for Disease Control and Prevention. “But now we see them every year,” she said.
This is partly explained by climate change.
Global warming expands mosquitoes’ habitat and allows them to breed all year round, rather than only in the warmer months. Warmer temperatures also cause viruses to replicate more quickly, meaning mosquitoes end up carrying many more viral copies, making it more likely that a person will become infected if bitten.
“We also see that dengue causes outbreaks at times when they don’t usually occur,” Ko said.
Dengue cases in South America were not only unusually high this year, but they also appeared unusually early in the season. Likewise, Puerto Rico, a place where dengue outbreaks can occur in the summer and fall, declared a public health emergency at the end of March, after the American territory was invaded by cases of dengue and more than 400 people were hospitalized.
In recent years, the epidemic has spread to parts of southern Brazil and northern Argentina, where dengue was not previously a big problem, Ko said.
“This gives us a glimpse of what we might see here in North America in the decades to come,” Ko said.
How could dengue take hold in the United States?
The fact that Aedes aegypti mosquitoes are found in places outside their normal range does not mean they carry the dengue virus, but these early insects are a warning of what could happen, Ko added .
Locally transmitted dengue infections — meaning the infected person did not become ill abroad — are still rare in the continental United States, but have recently been observed for the first time in some states . Last October, California health officials reported the first locally transmitted case of dengue fever in the state in Pasadena. Local transmission has also happened in Arizona, Florida and the south coast of Texas. Last summer, record heat waves hit Europe, where cases of local transmission of dengue have been observed in France, Italy and Spain.
“I think this means dengue will become more common,” Paz-Bailey said, adding that the main concern remains the significant increase in cases when the virus is already endemic.
This summer, she doesn’t expect to see significant dengue outbreaks in the continental United States, but she said some people would likely travel to areas where cases are higher than usual and bring the virus home. they.
“Travel-associated cases lead to small chains of outbreaks,” Paz-Bailey said.
Humans are reservoirs for dengue, so to have widespread transmission, enough people need to be infected so that mosquitoes can reliably bite a person carrying the virus so they can pass it on to another person.
“That’s why we’re seeing a dengue outbreak in Puerto Rico right now,” said Michael von Fricken, director of the One Health Center of Excellence at the University of Florida in Gainesville. “They have reached this tipping point where there are enough infected humans to then infect other mosquitoes that continue to transmit the disease.”
Florida recorded 176 cases of dengue so far this year, the vast majority involve people infected in other countries, most commonly Brazil or Cuba. The Florida Department of Health has recorded only seven cases of local dengue transmission in the state so far this year. Throughout 2023, the department documented 173 locally transmitted cases, most in Miami-Dade County.
What are the symptoms of dengue?
Dengue is caused by four viruses, so a person can be infected four times in their lifetime. Just about 1 in 4 people are symptomatic the first time they are infected, according to the CDC.
Ko said a person’s first symptoms are usually fever and headache. Fatigue, nausea, vomiting, a rash that looks like measles, and extremely painful body aches.
Most people recover within a week or two, but about 1 in 20 people develop severe dengue, which can be fatal. The more dengue a person is infected with, the higher the risk of complications.
“After your first exposure, your risk of experiencing dengue hemorrhagic fever or serious symptoms increases exponentially,” Von Fricken said. Dengue also becomes more deadly with each infection.
Although the United States has a dengue vaccine, it is only approved for children ages 9 to 16 who live in places where dengue is endemic, including Puerto Rico, American Samoa or in the US Virgin Islands.
Additionally, children can only receive the vaccine if they have already been infected with dengue. This is because if a person gets vaccinated and then gets their first dengue infection, they still run the risk of getting very sick, just as someone becomes sicker following a second infection. Since most Americans haven’t had dengue, “this vaccine is not very helpful” for most, Ko said.
There is no specific medication to treat dengue fever. Instead, doctors simply aim to treat symptoms and keep the patient comfortable until the virus runs its course. This means resting and drinking plenty of fluids. Ko said people should try taking acetaminophen (Tylenol) for pain and fever if they can, because nonsteroidal anti-inflammatory drugs (NSAIDs), which include ibuprofen and aspirin, can make bleeding worse if a person develops dengue hemorrhagic fever, in which their blood vessels become damaged and leak.
Paz-Bailey said it is important for people traveling to dengue-affected areas to stay in air-conditioned places when possible, use insect repellent and wear long sleeves and pants to avoid bites. of mosquitoes.
Bed nets can be helpful, but dengue-carrying mosquitoes typically bite during the day, so they may be less useful than they are in preventing other mosquito-borne diseases like malaria, Ko said.
At home, people can make their gardens less attractive to mosquitoes by reducing the amount of standing water, especially after a downpour.
“It is difficult to control the mosquito population, so we need to deal with it with everything we can and develop several strategies,” Paz-Bailey said. “No single strategy will be enough. »
This article was originally published on NBCNews.com
