New York: Researchers have developed a new method to pinpoint outbreaks of dengue fever by tracking phone calls to public health hotlines, a team of scientists said on Friday.

Analyzing patterns of calls in Pakistan’s Punjab region, the researchers forecast suspected dengue cases up to two weeks ahead of time with block-by-block accuracy, the researchers said in a study published in the journal Science Advances.

Dengue infections have increased dramatically over recent decades, making the virus the world’s fastest-spreading tropical disease, according to the World Health Organization (WHO).

The virus, which has flu-like symptoms that can develop into the deadly dengue hemorrhagic fever, causes around 390 million infections a year globally, the U.N. agency says.

Though dengue seldom causes death, a complication called severe dengue is a leading cause of death among children in some Asian and Latin American countries, according to the WHO.

The low-cost statistical method to track dengue is particularly adapted for nations lacking the resources to effectively monitor the spread of diseases, said the scientists from the United States, Pakistan and United Arab Emirates.

‘Thousands of lives are lost every year in developing countries for failing to detect epidemics early because of the lack of real-time data on reported cases,’ said co-author Lakshminarayanan Subramanian, a professor at New York University’s Courant Institute of Mathematical Sciences.

‘We think our technique can be of use to public health officials in their fight against the spread of crippling diseases.’

The method was tested in Pakistan in the aftermath of a 2011 dengue outbreak in Lahore in which 21,000 were infected, the study said.

Over two years the researchers tracked more than 300,000 phone calls in the city, Pakistan’s second largest, to a health hotline set up in the aftermath of the outbreak.

‘To the best of our knowledge, this system is the first to demonstrate ... that an accurate, locality-specific disease forecasting system can be built using call volume data from a public health hotline,’ said Subramanian.

Only one dengue vaccine is currently licensed, Sanofi SA’s Dengvaxia, with Mexico in December becoming the first country to give it approval.

But the three-dose vaccine was approved only for use in a limited population, people aged nine to 45 who live in areas where the disease is endemic, meaning younger children and tourists could not get it, and questions remain about its effectiveness.

In 2015, a spike in cases of dengue fever in Asia - including the Philippines, Myanmar, Malaysia, Taiwan and Vietnam - put medical services under strain.