In 2023, the Americas saw the highest recorded number of dengue cases of all time, with a total of 4,565,911 cases and 2,340 deaths, said the Pan American Health Organization (PAHO) in a recent call for stepped up efforts to control Aedes aegypti, the primary mosquito vector of the dengue virus.  

And already in the first six weeks of 2024, dengue cases have outpaced last year’s record, causing over one million cases, said PAHO in a recent epidemiological alert.  

Describing the increase as “exponential,” it said the current trend represents a 157% increase in infections this year over the same period as last year, and a 225% increase over the last five years. 

PAHO has called on member states to strengthen awareness campaigns, including stepping up community participation to reduce mosquito breeding sites and encouraging people to seek timely medical attention. 

Aedes aegypti mosquitoes typically breed in sites such as water containers as well as in urban waste, including items such as discarded tyres where rainwater often accumulates.

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. 

PAHO also emphasised the importance of continuing surveillance, early diagnosis, and timely treatment of dengue cases. 

PAHO also notes that monitoring chikungunya and Zika is also important as increases in dengue often indicate the circulation of these other mosquito-borne viruses, which can cause severe fever as well as premature birth and birth defects. 

Southern Cone worst affected

Some 80% of all dengue cases occur in the Americas region, but the Southern Cone sub-region including Argentina, Brazil, Paraguay, and Uruguay is worst affected. In 2023,  71% of cumulative cases were in this sub-region. 

Another seven countries and territories have seen a sharp increase in cases, including Colombia, Costa Rica, Guatemala, Guadeloupe, French Guiana, Martinique, Mexico and Peru, PAHO reports.

Dengue is also a serious problem in South East Asia where infection rates have increased by almost 50% in recent years. 

Worldwide, cases are projected to increase as warming climates, urbanisation, and shifting rainfall patterns allow Aedes aegypti to survive and thrive in previously unfavourable settings and regions.

State of emergency declared in Brazil

Brazil has been especially burdened with over 800,000 cases reported in the first six weeks of 2024, a fourfold increase when compared to last year. 

In the midst of the worst outbreak in years, four Brazilian states have declared public health emergencies as record heat and above-average rainfall has increased mosquito breeding sites. 

To make matters worse, all four dengue serotypes (DENV-1, DENV-2, DENV-3 and DENV-4) have been reported circulating in Brazil, as well as in Costa Rica, Honduras, and Mexico. 

Simultaneous circulation of the different serotypes increases the chance that an individual could become reinfected by another serotype more severely, shortly after having recovered from the first infection. 

In response, Brazil’s health ministry increased emergency public health funding, for dengue outbreaks and other emergency events to $300 million. 

These funds are to be directed to Brazil’s vaccination efforts. Brazil plans to vaccinate 3.2 million people this year, using the recently approved Japanese Takeda Pharmaceutical’s Qdenga vaccine. The vaccine was recently approved by the European Medicines Agency, but has only been used in Brazil thus far. 

The vaccine holds immense promise, but the real test will come in April, when dengue cases in the Americas are expected to peak.

Image Credits: PAHO/WHO, PAHO, PAHO .