New Delhi: The annual number of dengue fever cases in India was around 6 million between 2006 and 2012, about 282 times higher than average of 20,474 cases reported by ministry of health, according to a study published in the American Journal of Tropical Medicine and Hygiene.

The study, led by researchers at Brandeis University’s Schneider Institute for Health Policy in Waltham, Massachusetts, the INCLEN Trust International in New Delhi, and the Indian Council of Medical Research’s Centre for Research in Medical Entomology (CRME) in Madurai, Tamil Nadu, is the first to use systematic empirical data to estimate both the disease burden and the direct and indirect costs of dengue in India.

“We found that India had nearly 6 million annual clinically diagnosed dengue cases between 2006 and 2012—almost 300 times greater than the number of cases that had been officially reported," said Donald Shepard, lead author of the study and a health economics professor at Brandeis University.

According to the study, the disease inflicts an economic burden of at least $1.11 billion each year on India, in medical and other expenses.

Dengue, a viral disease transmitted by Aedes mosquitoes, is a serious global public health problem, infecting between 50 million and 390 million people each year in more than 100 countries. Symptoms of the disease range from mild fever and joint pain to potentially fatal haemorrhaging and circulatory shock. No effective anti-viral drugs exist to treat the illness, and large mosquito control efforts have thus far failed to stem the increasing incidence and spread of dengue epidemics.

In recent decades, dengue outbreaks in India have become larger and more frequent, with a greater number of severe cases and deaths, the report added.

“Good data on the incidence and cost of the illness have been lacking due to gaps in how information on individual cases is collected and reported," said Narendra Arora, executive director of INCLEN.

India is believed to have more cases of dengue than any other country in the world, and except for a slight dip in 2011, the incidence rate has grown steadily in recent years.

In 2013, India’s National Vector Borne Diseases Control Programme reported that the country had experienced an annual average of 20,474 dengue cases and 132 dengue-related deaths since 2007, but infectious disease experts believe those official numbers likely reflect only a small fraction of actual cases.

India had a major dengue outbreak in 2013, with more than 55,000 reported cases, triggered largely by the heaviest rains in two decades. Standing water provides a breeding ground for disease-carrying mosquitoes.

“Understanding the full extent of the economic and disease burden of dengue in India is necessary to help policymakers and public health officials prepare for and control future outbreaks of the disease," said Brij Kishore Tyagi, senior investigator, CRME.

The study analysed clinically diagnosed cases in public and private hospitals from a single district in Madurai which was extrapolated to the national level. It also looked at data from 10 medical college hospitals across ten different states of the country including public and private hospitals. The study used a Delphi panel which is a statistical tool comprising a structured group of experts to arrive at an estimate of the correct number of clinically diagnosed cases.

The researchers found that direct medical cost to India from this disease was around $548 million per year, or about $94.85 per patient.

However the direct medical cost of the disease represent only 49% of the overall cost which is around $1.11 billion annually, or $0.88 per year for every person in the country, the study added.

“There are other costs, most of which tend to be borne by individuals and households, such as the cost of traveling to and from treatment and lost income due to lost time at work," said study co-author Yara Halasa, a health economics researcher at Brandeis University.

The study was funded by Sanofi Pasteur, a contract vaccine maker which has a dengue vaccine in late-stage clinical development. However the company was not involved in the actual research, the report stated.