Global science race accelerates to crack dengue's deadly code

Dengue has become a global emergency that science is racing to solve. The numbers tell the story: in 2000, the world recorded roughly half a million cases. By 2024, that figure had climbed to 14.6 million. Projections suggest another 60 percent surge by mid-century as warming temperatures push mosquito habitats into regions that have never seen the disease. Against this backdrop, an international consortium called COMBAT has mobilized researchers across continents to crack the fundamental question that has eluded medicine for decades: why does dengue kill some people and spare others?

The project brings together scientists from Sweden's Karolinska Institute, institutions across Europe funded by the European Union's HORIZON program, and a substantial Indian contingent backed by the Department of Biotechnology. India's contribution is substantial and specific. A team led by Prof Arindam Maitra at the National Institute of Biomedical Genomics in Kalyani is investigating how human genetics influence susceptibility to severe dengue. They are joined by researchers from the Regional Centre for Biotechnology in Faridabad, the Manipal Institute of Virology in Udupi, and clinicians from Max Hospital in Delhi and Artemis Hospital in Gurugram. The strategy is to use advanced genomics to map which genetic variations and immune responses determine whether an infection stays mild or turns catastrophic.

Inside the laboratories, the toolkit has become remarkably sophisticated. High-resolution microscopy lets researchers watch the virus attack human cells in real time—a capability that would have seemed like science fiction a decade ago. Artificial intelligence systems are being woven into the research pipeline, learning from dengue data and then applying those lessons to other emerging pathogens. Perhaps most innovative are organ-on-chip models: miniature reconstructions of human organs that allow scientists to study infection safely without exposing people to experimental treatments. Several of these technologies are slated to be installed in Indian research institutes, expanding the country's capacity to conduct this work domestically.

While the basic research accelerates, vaccine development has entered a new phase. Takeda's tetravalent dengue vaccine, marketed as Qdenga, recently cleared India's regulatory hurdle for use in people aged 4 to 60. The vaccine shows 84.1 percent efficacy against dengue cases severe enough to require hospitalization, and it works regardless of whether someone has been infected before—a crucial advantage over earlier candidates that required pre-screening. More than 10 million doses have been distributed globally since 2023 across over 40 countries. Simultaneously, the Indian Council of Medical Research is running a Phase III trial of its own candidate, DengiAll, a single-dose recombinant vaccine being tested across 20 sites in 19 states and Union Territories. The trial has already enrolled more than 10,300 participants. Beyond vaccines, researchers at ICMR's National Institute of Virology in Pune are developing antiviral drugs—some repurposed from existing medicines, others derived from plants, and still others based on RNA interference technology—with several candidates now in preclinical stages.

The reason this work is so urgent and so difficult comes down to dengue's peculiar immunology. The virus exists in four distinct serotypes, all circulating widely. A person infected with one strain develops immunity to that strain but remains vulnerable to the other three. Here is where the danger emerges: if someone infected with dengue type 1 is later exposed to type 2, their existing antibodies can paradoxically make the second infection worse—a phenomenon called antibody-dependent enhancement. This means a vaccine must induce equal, durable protection against all four serotypes simultaneously. Any imbalance in the immune response could actually increase the risk of severe disease during a subsequent infection. The immune system itself complicates matters further by prioritizing responses to whichever strain it encounters first. These immunological barriers explain why dengue vaccines have been so hard to develop and why the COMBAT project's focus on understanding the underlying mechanisms of disease and host-virus interaction is so essential. The insights generated could directly reshape how future vaccines are designed.

Climate change is tightening the deadline. Over the past 20 years, global temperatures have risen approximately 0.9 degrees Celsius, expanding the geographic range of Aedes mosquitoes—the vector for dengue—into higher latitudes and previously unaffected regions. Temperature, rainfall, and humidity influence transmission patterns in ways that often show a lag of two to five months, making prediction possible but not prevention simple. The convergence of these forces—a virus that is spreading, a mosquito that is expanding its range, and a vaccine pipeline that is finally maturing—means the next decade will determine whether dengue becomes a manageable endemic disease or a pandemic threat. The work happening in laboratories from Delhi to Stockholm will shape that outcome.