Research reevaluates the economic burden of dengue on Puerto Rico
Northeastern University research posits a new estimate for the economic burden placed on Puerto Rico by dengue fever, which appears as an epidemic about every three to five years.
Every three to five years, Puerto Rico, a territory of the United States in the Caribbean, experiences epidemic levels of dengue fever, a disease carried by mosquitoes that causes a range of flu-like symptoms, including aches and muscle pains, nausea, headaches and fever.
A new study out of Northeastern University and the Centers for Disease Control and Prevention (CDC) says the annual economic burden that dengue places on the territory can exceed $1 billion.
Compounding the problem is the fact that the number of unreported cases — people with dengue who never report to a hospital, or whose physician flags it as a different disease — has also likely been underestimated, according to Michael Johansson, a research professor of public health and health sciences at Northeastern, who contributed to the study.
“We estimated there are about 15 cases that are actually occurring for every one that’s getting reported,” Johansson says.
Dengue is endemic in Puerto Rico, which means that the disease is regularly found there. In epidemic years, when the number of cases can spike well above 100,000, Puerto Rican hospitals can be overwhelmed by the number of cases, according to Johansson.
Treating mild cases of dengue often involves simple medication, like acetaminophen, and staying hydrated, while severe cases may require intravenous fluids or even blood transfusions, according to the Cleveland Clinic. While vaccines have been developed to treat dengue, Johansson says, the only one available for commercial use in the U.S. has been discontinued.
The study looks at the period from 2010 to 2023 to calculate the economic burden — a measure of how much money was spent on hospital and other medical costs, related medical costs such as meals and transportation to health facilities but also how much money was lost due to, for example, a sick person being unable to work.
In 2010, an epidemic year and the worst year for dengue cases in their study, over 144,000 in their estimate, the researchers calculated a total economic burden of over $1 billion, just under 1% of the territory’s entire annual gross domestic product, Johansson says.
By contrast, in 2014, the median year — a year that represents the middle of the range — they estimate 8,400 cases with an economic burden just under $63 million, according to the paper.
Johansson’s contribution to the study focused on the number of unreported cases and the effect these might have had on the total economic burden. He says that prior studies likely underestimated this number. “We know that dengue, like many diseases, [is like] an iceberg, and you only see the most severe cases,” he says.
To determine the actual number of cases, Johansson and his team had access to two fever monitoring systems installed across the island. These systems operate on a simple model. When a patient arrives at a clinic with a fever, a clinician asks if they would like to opt in to the monitoring system. If they choose to do so, they undergo additional tests free of charge to confirm the physician’s original diagnosis or potentially catch another disease such as chikungunya, Zika, dengue or several others.
Since any patient who arrived at a participating hospital with a fever and opted in was tested for dengue, these monitoring systems caught many cases that previously would have gone unrecorded. This data helped inform the researchers’ statistical analysis regarding how many at-home cases were likely found on the island but never wound up in a hospital.
According to the study, for every conventionally reported dengue case, there were 6-9 outpatient cases and another 5-8 hospitalized cases that nevertheless previously went unreported.
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Underreporting happens for a variety of reasons, Johansson notes. Many dengue cases are never serious enough to warrant a hospital visit, where clinicians would collect the data, and are taken care of entirely at home. Another complication is that dengue fever can be very hard to differentiate from other diseases like the flu, he said, which can lead to misdiagnoses and further underreporting of dengue case numbers.
Opting in also means that the patient’s anonymized data becomes available for studies like Johansson’s.
Maile Thayer, a CDC epidemiologist who worked with Johansson on the study, says that without the surveillance system, “It would not be possible to reliably estimate the true burden of dengue, as passive systems alone,” such as relying on physicians to report cases they encounter, can lead to significant undercounts.
Thayer hopes their findings will help guide policy makers in future efforts to combat dengue in Puerto Rico, especially when it comes to hospital planning, resource allocation and the cost-effectiveness of different strategies.
While dengue is not usually fatal, Johansson notes, “when you have lots of transmission, there are still people [who] die.”
He hopes that demonstrating just how high the economic burden is to Puerto Rico — which is a part of the United States — will help convince policy makers that “we should invest more in figuring out what the solutions are” to control the spread of the disease and mitigate its impact, he says.
