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Asia

India's fight against deadly dengue outbreak

India's capital New Delhi is once again in a grip of dengue fever, with at least 70 deaths according to unofficial accounts. Why is the South Asian country so prone to this virus, and what does it need to prevent it?

Five more people, including a 16-year-old boy, died in New Delhi on Tuesday, September 29, from dengue fever. This puts the death toll at over 70 in the Indian capital; however, the official count is still 17. Some 2,200 new dengue cases were reported last week alone, as New Delhi's hospitals continue to be flooded with patients affected by the disease.

The number of registered deaths nationwide related to this mosquito-borne disease in 2015 has so far been around 60. According to government figures, almost 27,7000 people across the world's second-most populated country have been infected with the virus this year, but the real figure is believed to be much higher than the official account.

"There was advanced warning that this was likely to be a high dengue season based on what we know about seasonality. But there has been little action from the government to prepare and a lot of scrambling to respond," Ramanan Laxminarayan, director of the Center for Disease Dynamics, Economics & Policy, in New Delhi, told DW.

Underreported dengue cases seem to be major issue in India. A study published last October by US and Indian researchers in the American Journal of Tropical Medicine and Hygiene found that an average of six million people a year in India had a symptomatic illness between 2006 and 2012 with dengue. The figure is nearly 300 times higher than officially reported.

What is dengue?

As Professor Arjen Dondorp explains, dengue is a viral infection, which is transmitted by a mosquito called aedes aegypti (and to a lesser extent aedes albopictus). A female mosquito gets infected by ingesting the virus from a patient when taking a blood meal (usually during the day time), and then can transmit the virus shortly after that when feeding on the next person.

Around 80 percent of people do not get ill from the infection, but the other 20 percent develop a severe form of disease - Dengue Hemorrhagic Fever (DHF), leading to fever, muscle pains, joint pains (nickname is break-bone fever), severe headache, nausea, and easy mucosal bleeds, Dondorp, who is the Deputy Director of Mahidol-Oxford Tropical Medicine Research Unit (MORU) in Bangkok, told DW. In some cases, the disease may cause death.

There are no specific drugs that are effective at killing the virus, so the treatment is supportive care, said Dondorp. "Giving intravenous fluids to the patients with shock is life-saving, where it is dangerous to give either too little or too much fluids. Blood transfusions may be needed if the patient has a bleed, usually from the gut."

The health expert said that creating drugs that could kill the virus effectively had proven to be difficult, but recently a vaccine was developed, which provided around 60 percent protection against the symptomatic disease.

Dengue and India's urbanization

Outbreaks in India - which recorded its first dengue epidemics in Kolkata in 1963-64 - usually happen in late and post-monsoon season. But as Dondorp points out, the virus is not restricted to the South Asian giant. "Dengue is a globally increasing problem; the number of cases has quadrupled over the past 30 years, and in addition to Asia, more and more cases have been reported from South America and to a lesser extent from Africa," Dondorp told DW.

"This increase is mainly caused by the wider spread of the aedes mosquitoes, which was facilitated by rapid urbanization in Asia and Latin America, resulting in more mosquito breeding sites," the expert said. Dengue epidemics, such as the current one in India, are relatively common and happen every few years in countries in South and Southeast Asia, Dondorp said.

But to which extent is India affected? Donald Shepard, a health economics professor at Brandeis University in the United States and lead researcher of the October 2014 study, explains that India has the highest number of dengue cases in the world. And this is due, in part, to India's large population.

"In incidence rates per population, parts of Southeast Asia and South America are highest," Shepard told DW. "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," he added.

And as Dr. Laxminarayan explains, population migration, rapid urbanization, poor sanitation and poor public health infrastructure are major causes for the spread and outbreaks.

Impact on economy

Professor Shepard also pointed out that the dengue situation in India could become more serious due to the fact that many cases go unreported in the country. "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," he said.

But while this process ensures that every case that is reported is really dengue, it may also 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.

18 year-old patient Radha, suffering from dengue, shares her bed with other patients in a casualty ward of a government hospital in New Delhi (Photo: Chandan Khanna/AFP/Getty Images)

Hospitals in the Indian capital struggle to cope with a flood of patients suffering from dengue fever

Shepard also explained that the virus is taking a toll on the Indian economy. "Including the lost productivity, the total cost was $1.1 billion per year. "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," he said.

How to limit infections

But why are India and other countries failing to tackle the issue? Experts point out that the main tool currently available to tackle dengue is the vigorous control of mosquito 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. Furthermore, mosquitoes can find hidden breeding sites in underground drains that people cannot see.

Shepard therefore recommends a series of steps to reduce the number of infections. "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," he said, adding that a careful implementation of these steps needed commitment from the public and government.

"We also need more tools and resources to control the disease," pointed out Shepard.