Nipah virus: Third outbreak in India, here's why deadly virus has re-emerged

This is not the first time India is witnessing an outbreak of the deadly Nipah virus that has claimed 14 lives in Kerala so far. There are reports of suspect cases in other states as well. The virus had first emerged in 2001 and then again in 2007. But why has the virus resurfaced?

Reasons of Nipah outbreak in India

Rapid urbanisation along with changing climate in recent years have been attributed to the emergence of Nipah virus in the country. Health experts suggest that due to rapid urbanization animals and birds including bats are losing their natural habitats. This has resulted in humans coming in contact with the animals that cause outbreak of numerous diseases.

According to environmental experts, Nipah virus has existed in bats for centuries and has not undergone an evolutionary change.

Experts reiterate that although there are many ecological factors that contribute to the emergence of Nipah virus, the most prominent is human intervention into bat-infested areas. In Malaysia the virus spread due to unplanned deforestation of pulp wood, which is the natural habitat for NiV carrying bats, and mismanagement of large piggeries.

It is believed that the increase in the human-bat interaction could be one reason why NiV outbreak occurred in Bangladesh and India where humans got this virus from drinking date palm juice contaminated by bat urine or saliva.

India’s first to encounter with the Nipah virus

According to the World Health Organization (WHO), Nipah virus was first identified during an outbreak of diseases that took place in Malaysia in 1998. Both animal-to-human and human-to-human transmission have been documented.

Since 1998 to 2015, more than 600 cases of Nipah virus human infections have been reported. Subsequent outbreaks in India and Bangladesh have occurred with high fatality rate. The first identification of Nipah virus as a cause of an outbreak of encephalitis was reported in 2001 in Meherpur district of Bangladesh. Since then, outbreaks of Nipah virus encephalitis have been reported almost every year in select districts in the neighbouring country.

India reported two outbreaks of Nipah virus encephalitis in the eastern state of West Bengal in 2001 and 2007. Around 71 cases with 50 deaths (70 percent of the cases) were reported in the two outbreaks.

During January and February 2001, an outbreak of febrile illness with neurological symptoms was observed in Siliguri, West Bengal. A second outbreak was reported in 2007 in Nadia district of West Bengal.

Around 30 cases of fever with acute respiratory distress and/or neurological symptoms were reported along with five deaths. All five victims were positive for NiV.

In the 2007 outbreak, a horde of bats were observed hanging from trees around a patient's residence which suggests direct contact with bat fluids.