India figures prominently in the first global map of Hepatitis E virus hotspots and the threat is maximum for those living in the Ganges basin.

What makes the risk even more worrying is the fact that there is barely any data on the viral load in the mighty river for Hepatitis E, a disease that afflicts lakhs every year.

Viral hepatitis is a cause for major health care burden in India and is now equated as a threat comparable to the big three communicable diseases – HIV/AIDS, malaria and tuberculosis.

Contaminated water is the main source of two such infections (Hepatitis A and E) in the developing world including India.

The proxy pathogen used by the regulatory agencies like the Central Pollution Control Board to keep a check on the river health is not a very appropriate one, according to two Swiss scientists who created the map.

The hot spot map, which relies on published scientific data on Hepatitis-E outbreaks, shows two clear regional groupings – a large area in the Indo-Gangetic plains stretching up to Punjab in the north and Andhra Pradesh in the south, mostly due to contaminated water.

The scientists found that 27% of all reports of water-related outbreaks caused by Hepatitis E since 1987 have occurred in the north of India (Ganges basin).

The main source of freshwater in the region, one of the most populated in the world is the Ganges, the third largest river on the planet by discharge and highly polluted.

"Most of the outbreaks that occur regularly in India are located in the Ganges watershed, in proximity to the river or its effluents," Anna Carratala, a scientist at Swiss Federal Institute of Technology Lausanne (École Polytechnique Fédérale de Lausanne or EPFL) and one of the authors of the study told DH.

An additional source of uncertainty, she said, was the actual concentration of the pathogen in the Ganges as there is almost no paper to date describing the concentration of the virus in the river. In most cases, the presence of fecal pollution in the river is assessed by analyzing Escherichia coli, which is not representative of pathogens like Hepatitis-E or rotaviruses.

According to the World Health Organization, there are around 20 million HEV infections worldwide every year and some 50,000 deaths from the disease.

Hepatitis E epidemics are particularly deadly for pregnant women and generally occur after heavy rains and floods or after months-long droughts.

To prepare the hot-spot map, published in the journal Scientific Reports on Thursday, they factored in geographical location, population density and the rate of evapotranspiration, or how much river water evaporates during a drought.

The last parameter is crucial because the more that occurs, the more highly concentrated the intestinal pathogens are in the contaminated water that remains - water that is often used for cooking, washing or even religious ceremonies.

“On the Ganges watershed, our results suggest that water balance can be important to modify the concentration of the water in the river. The hypothesis is that more water leads to lower virus concentration and hence less outbreaks. But there is not yet not enough information to validate this hypothesis. More studies are needed in the area,” she added.