India may be grossly under reporting dengue cases. A study published in the American Journal of Tropical Medicine and Hygiene on Tuesday has found that in the period 2006-12 there were an average of nearly six million cases annually — 282 times the annual average of 20,474 cases reported by the Ministry of Health.

According to the joint study by the INCLEN trust, ICMR, the National Institute of Health and Family Welfare and Brandeis University in Massachusetts, “The National Vector Borne Disease Control Programme (NVBDCP) captures only 0.35 per cent of the clinically diagnosed dengue cases in India”.

The study analysed retrospective data from 10 medical colleges across five regions of the country and the clinically diagnosed cases in public and private hospitals from a single representative district, Madurai, which was extrapolated to the national level. It also used a Delphi panel, a statistical tool comprising a structured group of experts, to arrive at an estimate of the correct number of clinically diagnosed cases. The study puts the economic costs of dengue at $1.11 billion or $0.88 per capita and says that 80 per cent of the treatment expenses went to private centres. The study has been funded by Sanofi which, the authors said, was not involved in the process.

According to Dr N K Arora, from the INCLEN trust, who is the corresponding author of the study, “To estimate the total disease burden, first we collected data from all government and private hospitals and nursing homes from a single district to arrive at an adjustment factor on the total number of cases. Based on national data, this factor was then extrapolated to the national level.”

According to Dr Arora, the main reason for this gross under reporting was the absence of private sector data. The cost of a hospitalised episode in the public sector came to $197.03, and $ 248.11 in the private sector. For ambulatory or out patient treatment, the cost in the public sector was $ 23.49 and $ 26.09 in the private sector. Senior government officials said the study had also considered suspected dengue cases from the private sector. According to a senior official from the NVBDCP of the Ministry of Health, which supplied the national data for the study, “The study includes reporting from private hospitals, which primarily rely on rapid diagnostic tests. The kits have limitations in sensitivity and specificity. We consider them to be probable or suspected cases and not confirmed ones.” Explaining that the government had not missed out on this data “entirely”, the official explained, “During this period, while our confirmed cases were over 22,000, the data on suspected cases was four-five times more. Since 2012, most states are also trying to get data from private hospitals”.