Dengue virus cases have reached an all-time high since January in the US territory of Puerto Rico, with 1,729 people infected so far – a more than 300% increase compared to last year.
The uptick in the mosquito-borne disease, which causes mild to severe illness, follows a trend across the Caribbean region. The total number of reported cases for the Caribbean has reached nearly 57,000 – a 469% increase as compared to the same period in 2023.
Climate change, the El Nino effect, and unplanned urban growth have fueled this year’s surge.
While dengue tends to hit Brazil, Argentina, Paraguay and Uruguay the worst, the Caribbean, the Central American isthmus, and Mexico continue to see above-average transmission.
Further complicating efforts to control the mosquito-borne disease is the premature start to the hurricane season. Hurricane Beryl has already devastated several small island nations in the Caribbean, damaging water and health infrastructure, thus making residents even more vulnerable to dengue.
Halfway into 2024, the total burden of dengue cases in the Americas has exceeded 10.1 million, more than twice the 4.7 million cases in 2023.
The Puerto Rican Department of Health recently extended its dengue epidemic alert until December, after this year’s season brought the highest proportion of severe dengue in the Americas.
Of the nearly 2,000 cases reported to the territory’s health officials, 92 are severe, meaning patients may suffer from painful symptoms including fever, headaches and vomiting. Three of the dengue serotypes – DENV 1, 2, and 3 – are currently circulating.
This alert comes just two weeks after the US Centers for Disease Control and Prevention (CDC) issued a health advisory warning of the increased risk of dengue virus infections in the US. While most cases in the continental US come from overseas travelers, Florida has reported a handful of locally-transmitted cases.
Hurricane Beryl sets back health response
The first category 5 hurricane of the season, Beryl devastated much of Saint Vincent and the Grenadines, Grenada, Dominica, Barbados, and Jamaica. The destruction left in the hurricane’s wake highlights small island nations’ vulnerabilities to climate change and its health effects.
The Caribbean region is particularly susceptible to healthcare disruptions from natural disasters. Studies of cyclones in China and hurricanes in Puerto Rico found increases in dengue virus infections in the weeks following hurricanes.
“Pre-existing environmental health risk magnified after the pass of Hurricanes Irma and María,” said researcher José Pérez-Ramos, Assistant Professor of Public Health Sciences at the University of Rochester. He notes that in the aftermath of 2017’s devastating hurricanes, participants in the study were worried about frequent dengue outbreaks.
While the International Federation of the Red Cross (IFRC) and other relief organizations active in the Caribbean nations are in the early days of response and assessment, the confluence of the hurricane’s destruction and peak dengue season may spell out an increased case burden.
“Hygiene kits, cleaning kits, tool kits, kitchen sets, tarpaulins, blankets and mosquito nets have already been dispatched to the hardest hit islands to meet the immediate needs of the affected population,” said Rhea Pierre, IFRC Disaster Manager for the English and Dutch-speaking Caribbean. “Still, rapid damage assessments show that the devastation is massive.”
‘A notable increase’ in cases, but low fatality rate
Despite this year’s record number of cases, the World Health Organisation’s (WHO) regional office in the Americas, the Pan-American Health Organization (PAHO), notes that the fatality rate for the Americas has not exceeded the regional benchmark of 0.05%.
“While we are seeing a notable increase in the number of dengue cases in the region this year, it is important to highlight that the proportion of cases that progress to death remains low thanks to countries’ efforts and the support of PAHO,” said Jarbas Barbosa, PAHO Director, in a recent press release.
“This situation highlights the importance of sustaining surveillance, strengthening prevention and control measures, and ensuring timely medical care,” he added.
Few studies have assessed what causes some patients to progress to severe dengue. The WHO notes that ensuring access to sufficient medical care should remain at the forefront of countries’ priorities to treat severe dengue.
PAHO’s Caribbean Mosquito Awareness Week, which took place in May, aimed to raise public awareness about the connection between mosquitoes and the diseases they transmit, such as dengue, chikungunya, and Zika, and to involve the community to prevent mosquito breeding.
“The population and household members should be encouraged to eliminate sources of mosquito breeding, both household and peri-household. This is everyone’s task: the family, the community, the public and private sector,” said PAHO in a recent alert on increased cases in Central America, Mexico, and the Caribbean regions.
Aedes aegypti, the main mosquito vector, typically breeds in sites such as water containers as well as in urban waste, including plastic wrapping that can accumulate rainwater.
As the virus doesn’t have a cure and repeat infections can even be more severe, surveillance and control of mosquito breeding sites is critical to reduce dengue transmission and illness, particularly the most severe form of the disease, dengue hemorrhagic fever.
Dengue cases expected to rise in Mexico, Central America and Caribbean
Farther north of the equator, cases have yet to peak in the PAHO regions of the Caribbean, Central America Isthmus and Mexico.
“Although there has been a decrease in dengue cases in the Southern Cone [Brazil, Argentina, Paraguay, and Uruguay] and Andean sub-regions in recent epidemiological weeks, the subregions of the Central American isthmus and Mexico, and the Caribbean subregion are entering the period of increased dengue circulation, which could significantly increase the number of cases reported in the Region during the second half of 2024,” said PAHO in their May epidemiological alert.
Cases decreasing at tail-end of season
The number of dengue cases is finally tapering off for the South American countries hardest hit – Brazil in particular saw an explosive growth in cases earlier this year. PAHO attributes the country’s epidemic conditions to prolonged heat, higher rainfall levels, as well as decreased population immunity following COVID-19-related restrictions.
In response, and to avoid losing vaccine stock to expiration, the Brazilian government recently expanded the population eligible for dengue vaccination. Now, children six to sixteen are eligible, rather than just ten to fourteen year-olds.
Image Credits: Direct Relief/Felipe Luna, James Gathany/ PHIL, CDC, Public Domain, IFRC, PAHO , PAHO , PAHO.
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