Expanding Dengue: Rising Temperatures Trigger Surge in Cases Across New Regions

 

Expanding Dengue: Rising Temperatures Trigger Surge in Cases Across New Regions

Numerous countries have experienced a significant surge in dengue fever cases during 2023, a trend experts attribute to the impact of a warming climate and increased global mobility. The looming El Niño weather phase, expected to bring prolonged warmer Pacific ocean temperatures and elevated global temperatures, is raising concerns about a potential exacerbation of the situation.

Christian Requena, the regional head of the national medical association in Piura, the hardest-hit region in Peru's record-breaking dengue outbreak from March to July, emphasizes the need to learn from the past experiences of the COVID-19 pandemic. He warns that the impending climate phenomena could have disastrous consequences.

Dengue, now endemic in most Latin American countries, is spreading into new areas worldwide, with a significant rise in cases this year. The warming climate is not only expanding the geographic range of dengue-carrying mosquitoes into temperate zones but also accelerating breeding and transmission rates.

By late September, several nations including Bangladesh, Sudan, Argentina, Bolivia, Jamaica, Peru, Sri Lanka, and Thailand had issued warnings and were on alert due to the dengue outbreak. Dengue, a mosquito-borne disease prevalent in 130 countries, can manifest as high fevers, body aches, nausea, and rashes, with severe cases having the potential to be fatal. There is no specific treatment or cure, and its incidence has been increasing steadily, with an eight-fold rise between 2000 and 2022, putting over half the world's population at risk, according to the World Health Organization.

Experts stress that swift responses, aided by local communities in eliminating mosquito breeding sites, are crucial in preventing dengue outbreaks. Simultaneously, the scientific community is actively developing vaccines and innovative methods to combat the mosquito responsible for dengue transmission.

Dengue, although overshadowed by malaria historically, may see an increase in attention and funding as rising temperatures are expected to reduce the Anopheles mosquitoes responsible for malaria transmission while expanding the range of the Aedes species, which transmit dengue. As entomologist Michael Macdonald predicts, "Malaria will soon be in the past, but dengue is the future."

The situation in Peru, with the highest case fatality rate in the Americas this year, offers a glimpse of the potential crisis if the predicted El Niño event materializes. El Niño typically brings elevated temperatures and unusual rainfall patterns, impacting regions as far away as northeastern Brazil, where dengue cases have surged this year. The 2017 occurrence of a local "coastal El Niño" event off the coast of Peru resulted in warmer weather, heavy rain, and increased dengue cases.

The sluggish post-flood recovery, complicated by the COVID-19 pandemic, left Peru unprepared for this year's flooding and the subsequent dengue outbreak. Primary care clinics and hospitals in Piura lacked adequate infrastructure, equipment, and medical personnel. By mid-September, Peru had reported over 250,000 cases and 419 deaths, with over 75,000 infections in Piura alone. A shortage of essential medications and poor coordination within the healthcare system exacerbated the crisis, leading to the resignation of the health minister in June.

Addressing the looming threat of arboviruses transmitted by Aedes mosquitoes, including dengue, zika, chikungunya, and yellow fever, requires comprehensive long-term planning and an integrated management strategy, according to Requena.

Dengue is closely linked to stagnant water, where mosquitoes breed, which increases with unexpected rains and rising temperatures. Identifying breeding sites and responding promptly is essential to prevent outbreaks. Governments tend to allocate emergency funds only once an outbreak is underway, and humanitarian aid arrives late, exacerbating the crisis.

Aedes mosquitoes typically stay within a small area, laying their eggs in damp places, which predominantly affects low-income neighborhoods. Control programs that use larvicide often focus on household containers, while the actual problem areas are frequently outdoor locations such as discarded items where rainwater accumulates.

When dengue cases surge, health workers usually resort to indoor and outdoor fumigation, but experts argue that these late responses are often ineffective. Targeting areas where mosquitoes settle, such as indoor walls and using spatial repellents, is deemed more effective.

Alternative measures include vaccines, with one approved by the US FDA and the EU for individuals with prior dengue infection. Several other vaccines are under testing. Additionally, the World Mosquito Program is experimenting with a bacterium called Wolbachia, which interferes with mosquito saliva's ability to transmit arboviruses, potentially reducing dengue cases. However, scaling up this approach may be challenging, and concerns about viral mutations persist.

In the face of an escalating dengue crisis, it is imperative for nations to implement proactive measures, enhance healthcare infrastructure, and invest in research and development to mitigate the impact of this deadly disease.