Dengue fever hits record 12.7m cases with 4 billion feared at risk in world's largest outbreak

Cases of have reached record highs with infections , putting an estimated 4 billion people at risk.

According to the , cases peaked in 2023 with 6.5m reported globally – but 2024 has seen the highest number on record with 12.7m cases so far – almost double last year’s figure. Dengue fever, also known as ‘break-bone fever’, is a viral infection transmitted to humans from the bite of infected mosquitoes.

It is most prevalent in tropical and sub-tropical climates worldwide, primarily in urban and semi-urban areas, with Brazil seeing a particularly concerning outbreak, reporting over 9.5 million cases this year. Most people who contract it will show no symptoms, but for those who do, the most common symptoms include high fever, headache, body aches, nausea, and rash. The majority of patients recover within one to two weeks.

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Some people can develop severe dengue and require care, and in extreme instances, it can be fatal. More than 8,700 people have died from Dengue fever in 2024 so far. The World Health Organization estimates that 4 billion people are at risk of dengue and related viruses, with the figure rising to 5 billion by 2050.

WHO director-general Dr Tedros Adhanom Ghebreyesus says the rapid spread in recent years is “an alarming trend.”

Deadly combination of risk factors

There are a number of risk factors that, when combined, make people more susceptible to developing serious symptoms of Dengue fever. The highest case numbers in recent years have been seen in Latin America and parts of Africa and south-east Asia. But infections have also spread to mainland Europe.

The climate crisis, increased migration and urbanisation may be driving the outbreak, says Prof Sophie Yacoub, head of the dengue research group at Oxford University’s clinical research unit. The Guardian reports that the mosquitoes carrying dengue can survive in higher temperatures and can breed in a tiny amount of standing water.

Yacoub adds: “A lot of people dismissed it as another viral illness – but actually we are seeing some higher mortality now. There are similar risk factors to Covid-19 – so people with obesity, or diabetes, or other comorbidities have a higher risk of getting severe dengue and higher mortality. And I think as dengue is affecting many countries that have also increasing obesity or diabetes, these two pandemics are kind of colliding.”

Clinical trials and vaccines

Unlike other viral infections, Dengue has no particular treatment other than to provide hospital care to those who need it, where the body is supported while it fights the infection. An antiviral set to be developed by Johnson & Johnson was scrapped earlier this month.

Efforts are underway to start a massive global trial, examining various treatments concurrently - a strategy reminiscent of the Recovery trial which, amid the Covid-19 crisis, confirmed that the affordable steroid dexamethasone could be beneficial for patients. "It would just be a constantly recruiting platform trial across 10 different countries, with thousands of patients being enrolled," Yacoub says. "That kind of size trial is what we need to really generate that robust evidence."

Meanwhile, two vaccines against dengue have been brought to the market. But the first, Dengvaxia, only works for those who have had a prior infection. The second vaccine, known as Qdenga, appears more promising and is currently being administered in to tackle rising cases within known dengue hotspots.

The traditional remedy route

While the public awaits the release of new medicine to help tackle the virus, many are turning to traditional remedies, particularly those in Dengue hotspots.

These include papaya tea, often on the advice of medical professionals, though there is yet to be any concrete scientific evidence back its use. In one case, a family used Pepto-Bismol paracetamol and coconut water to help treat their 16-year-old son who caught dengue while on holiday in Tobago, the Guardian reports.

According to Dr Michael Head of the University of Southampton, compounds in papaya may have an impact on blood clotting, but it is not known what an effective dose would be. He said: “Given dengue is a high burden and occasionally serious infection, treatment options would be useful.

“Further research into potential antivirals, whether based on papaya or anything else, are likely to be required for long-term global control of dengue fever.”