Researchers have suggested they may have found vital clues which could help to develop a vaccine for dengue fever.

By looking at how the human body fights the condition, scientists believe they may have discovered why people who get infected repeatedly by the mosquito-transmitted infection experience increasingly severe symptoms.

In a report published in the journal Science, researchers stated that the immune systems of those who have been affected by one strain of the disease contain prM antibodies which "spring into action" when a different variant is encountered.

The presence of these antibodies allows the second infection to establish itself, rather than combating the illness.

Professor Gavin Screaton, study leader and head of the Department of Medicine at Imperial College London, said: "We hope that our findings will bring scientists one step closer to creating an effective vaccine."

There is currently no vaccine for the disease, which is considered a deadly global health risk.