Science News

Dengue cases under-reported in India: study

K. S. Jayaraman

doi:10.1038/nindia.2014.135 Published online 7 October 2014

India has been under-reporting dengue cases, according to a new study that says there were 6 million cases during 2006-2012 — about 282 times greater than what was officially reported1

The mosquito borne disease inflicts on the country an economic burden of at least US$1.11 billion each year ($0.88/capita) in medical and other expenses, much of it in the private sector paid mostly by households.

The researchers from 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 claim this is the "first study to estimate the disease burden and direct medical cost of dengue in India using empirical data."

Dengue, a viral disease transmitted by Aedes mosquitoes, is a serious global public health problem with 2.5 billion people at risk in more than 100 countries. From the first case in Calcutta in 1945, India has experienced dengue epidemics since 1968. India’s selective surveillance system reports cases from 347 Sentinel Surveillance Hospitals and 14 Apex Referral Laboratories. In 2013, India’s National Vector Borne Diseases Control Program (NVBDCP) reported that the country had experienced an annual average of 20,474 dengue cases and 132 dengue-related deaths since 2007.

"According to our study, the NVBDCP captures only 0.35% of the annual number of clinically diagnosed dengue cases in India," the report says. To determine the annual number of dengue patients in India, the researchers collected data on patients who had been hospitalised with the disease in the Madurai district of the state of Tamil Nadu during a three-year period (2009-2011). 

They found that only one out of 282 clinically diagnosed cases had been admitted. They then used this "adjustment factor" and information from a panel of dengue experts, to calculate a national estimate for annual dengue cases, including ambulatory cases (ones in which the patient was treated but not hospitalized) for the whole country. Through this analysis the researchers concluded that the projected annual average of dengue cases in India is 5,778,406 in stark contrast to the reported 20,474. 

To estimate the cost of each dengue case, the researchers analyzed the medical records of 1,541 dengue patients who had been treated in 10 public and private medical college hospitals across India from 2006 through 2011. Gaps in those data were then filled in by interviewing 151 patients who had received care at a medical college hospital in Mumbai in 2012 and 2013. In the final part of the study, the researchers used those cost findings, along with the results of the Madurai analysis, to estimate the total annual economic burden of dengue in India. 

The report concludes that the economic and disease burden of dengue in India is substantially more than captured by officially reported cases, and increased control measures such as "vaccine and innovative vector control measures" merit serious consideration.

Payyalore Rajagopalan, a leading medical entomologist and former director of Vector Control Research Centre  in Pondicherry  says he is "very sceptical"  of the study's conclusion based on extrapolating the empirical data from just one district — Madurai — to the whole country. "It looks to me like a sales pitch for dengue vaccine." 

The authors admit their work was funded by Sanofi Pasteur, the pharmaceutical major which has a dengue vaccine in late-stage clinical development but say  the company had no control over the content or preparing the study for publication.


1. Shepard, D. S. et al. Economic and Disease Burden of Dengue Illness in India. Am. J. Trop. Med. Hyg. (2014) doi: 10.4269/ajtmh.2012.12-0157