Under-reporting dengue

According to the study by US and Indian researchers, an average of six million people a year in India had a symptomatic illness between 2006 and 2012 with this mosquito-borne disease.

The figure is nearly 300 times higher than officially reported. India is believed to have more cases of dengue than any other country in the world, with major outbreaks in recent years.

The study, published on Tuesday, October 7, in the American Journal of Tropical Medicine and Hygiene, says that the virus costs the country at least 1.1 billion USD each year in medical and other expenses.

In a DW interview, Donald Shepard, health economics professor at Brandeis University in the United States and lead researcher of the study, talks about the reasons behind the under-reporting and what India and other nations must do to tackle the disease.

DW: What are the main findings of the report?

Donald Shepard: The economic and disease burden of dengue in India is substantially more than captured by officially reported cases.

Between 2006 and 2012 India reported an annual average of 20,474 dengue cases. But after taking into consideration the underreported cases based on findings from a case study in Madurai district and an expert Delphi panel, the study yielded an annual average of 5,778,406 clinically diagnosed dengue cases between 2006 and 2012, or 282 times the reported number per year.

Moreover, the total annual direct annual medical cost during this period was 548 million USD. If you include non-medical and indirect expenses, the total economic cost amounts to 1.11 billion USD. In light of this situation, increased control measures merit serious consideration.

Why has the number of dengue fever cases in India been largely under reported?

First, in India, as in other countries, the surveillance system is necessarily selective. It serves to monitor trends and patterns, but cannot pick up every case. Users of the data may forget that fact. Second, the system reports only lab confirmed cases, using the lab tests approved through the surveillance system.

This process ensures that every case that is reported is really dengue. But it may miss many suspected cases that were not seen or reported by a health facility. Furthermore, there is the possibility that the tests used at the time failed to detect recently acquired dengue infections.

How widespread is dengue fever in India?

In terms of numbers, we think that India has the highest number of dengue cases in the world. This is due, in part, to India's large population. In incidence rates per population, parts of Southeast Asia and South America are highest.

However, due to growing urban populations and travel in India, the country’s incidence rates are substantial. Without additional control measures, numbers of cases are likely to continue to increase.

What impact is this having on the Indian economy?

Including the lost productivity, the total cost was 1.1 billion USD per year, as noted above. India's health system, particularly its major public hospitals, is severely challenged. For instance, beds used to treat dengue patients are not available for managing other illnesses, such as pneumonia.

Why are India and other countries failing to tackle dengue?

The main tool currently available to tackle dengue is the vigorous control of mosquito breeding sites. Containers that can collect clean water in close proximity to people are dangerous breeding sites.

These include water storage tanks on roofs, gutters, drip pans from air conditioners, flower pots, water storage vessels in homes, and discarded tires and plastic containers.

Trash should be removed. Containers should be sealed to keep out mosquitoes, cleaned to allow drainage, changed at least once a week, or treated with temephos or another product to stop mosquito breeding.

Carefully implementing these steps needs commitment from the public and government. Furthermore, mosquitoes can find hidden breeding sites in underground drains that people cannot see. We also need more tools and resources to control the disease.

What more can India and the international community do to effectively fight the disease?

New tools such as vaccine and novel mosquito control approaches look promising and need to be implemented as they become available.

Donald S. Shepard is a health economics professor at the Heller School for Social Policy and Management, Brandeis University in the United States.