Dengue fever is caused by a virus that is spread from person to person by blood-sucking mosquitoes.
The symptoms vary wildly with some people showing no sign of infection, others have bad flu-like symptoms, while some are killed by dengue.
The disease is commonly known as “break-bone fever” because it causes severe pain in muscles and bones. In the worst cases, people develop “dengue haemorrhagic fever”, which kills 25,000 people a year around the world. “It doesn’t kill as many as malaria, but it causes an enormous amount of sickness and it is fundamentally a big problem,” said Prof Cameron Simmons, from the World Mosquito Programme.