Millions of Cases of Dengue Fever Are Going Unreported in India

An independent study says the government reports 20,500 cases a year on average when the actual number is likely closer to 6 million.

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Oct 7 2014, 6:30pm

Dengue fever is often referred to in India as "break-bone fever" because of the severe joint pain it causes, but aching joints and delirium aren't the only effects feared by those at risk of infection—it can kill, and it's more widespread than officials say.

According to a new study published in The American Journal of Tropical Medicine and Hygiene, the Indian government has been systematically underestimating the number of dengue fever cases, reporting 20,500 cases a year on average when the actual number is likely closer to 6 million.

The Indian government uses a selective reporting system for dengue fever that encompasses 347 hospitals and 14 specialized labs in the country. Sentinel surveillance, as it's known, is a common technique used by organizations to signal outbreaks in locales where they're likely to occur

The problem with sentinel surveillance is that it renders diseases that are already endemic severely underreported. According to the study, this system lets millions of infections slip through its net by missing cases treated in ambulances and in hospitals not monitored by the government.

To correct the inaccurate estimates, the researchers gathered data from all the public hospitals treating dengue fever in the Madurai district, located in Tamil Nadu. Data from a stratified sample of the private hospitals in the area was also collected. These numbers were complemented by data obtained from a retrospective study of dengue fever cases in 10 medical colleges spread throughout India, estimates from experts participating in a panel discussion, and state-supplied data.

Using this information, the researchers were able to estimate the amount of hospital-treated and ambulatory cases of dengue fever in the region, and extrapolate that number to the rest of the country. 

While the authors note that their study has the limitation of being focused on Madurai, its findings are more generalizable than the numbers the Indian government holds to. Because the government's dengue reporting is likely better in Tamil Nadu than the other regions where they collected data, the researchers say that their estimate may even be low.

Anti-mosquito fogging in Ramachandrapuram Village, India. Image: Wikimedia

Far more concerning than the geographical limitations of the study are the institutional barriers the researchers faced when trying to collect their data. According to the authors, some hospitals are not authorized to release records relating to patients who were untested for dengue, but treated as if they had contracted the disease, leaving many potential cases unreported.

Moreover, the researchers reported conversations with health care workers that indicated government complicity in obscuring the number of dengue fever cases. "Indeed, some anecdotes suggested that even if the cases were clinically diagnosed as dengue, health providers were reportedly advised to report them as pyrexia of unknown origin," the authors wrote. In other words, the Indian government may be reporting dengue cases as generic fevers.

The reasons for the staggering disparity between the official estimates and those of the study appear to be many-pronged, relating to reporting procedures, the efficacy and use of dengue fever test kits, and the willingness of hospitals to turn over data.

Dengue fever, which appears in all tropical and subtropical regions, was first identified in India in 1945. The country experienced its first major outbreak in 1996, and 8,900 cases were reported. Approximately 373 of them were fatal. 

Since then, outbreaks of dengue fever have returned with the monsoons on an annual basis, transmitted into people's bodies by innumerable mosquitos than can hardly be avoided. Along with the fever come the stories of hospitals running out of beds for all the patients, and Indian doctors pleading with the government to accurately report the exploding number of infections.

According to the researchers, India's burgeoning presence in the global economy and its 2.1 percent share of all international travel make dealing with dengue an issue that goes beyond India's borders. 

"Climate change, the expansion of dengue vectors to new geographic regions, increasing human movement across borders, global trade, and urban migration collectively have changed the scope and scale of dengue fever from a national to a global concern," they wrote.