Lilawati Awasthi is used to the risks that come from living in a remote mountainous district in the far west of Nepal. Floods, landslides and treacherous roads are a part of daily life. But this year she faced a new hazard: mosquitoes carrying a mystery illness.

When she began to feel sick in September she was not overly concerned at first. “I thought it was a simple fever, but it wouldn’t go away,” says the 50-year-old. “We went to the hospital and it turned out I was suffering from dengue.”

Awasthi is one of more than 14,000 Nepalis who have been diagnosed with dengue fever since May, in an unprecedented outbreak that has left health professionals and the government reeling. Some experts believe the actual number of infections to be closer to 140,000. Six people have died.