Climate change increasing risk of new emerging viruses in India, say experts

New Delhi: Changing climatic conditions, particularly temperature and moisture variations following events such as extreme rainfall in some places and drought in others, will lead to a surge in the spread of vector-borne and infectious diseases across India, say scientists.

As concerns mount over the recent increase in respiratory viral infections, including H2N3, adenoviruses and swine flu, in many parts of India, the scientists said it might be too early to attribute it to climate change. But is definitely plausible.

The prospect of climate change leading to an increased burden with the spread of diseases such as dengue, chikungunya and malaria looms large.

According to public health expert Poornima Prabhakaran, steadily rising temperatures affect the pattern of transmission of disease agents like viruses as well their vectors through a number of pathways.

“These include changes in the incubation period, the transmission potential and the duration of transmission - all of which can impact the trends of diseases,” Prabhakaran, director, Centre for Environmental Health at Public Health Foundation of India (PHFI)

said. Incubation period is the time between exposure to a pathogenic organism and when symptoms and signs are first apparent.

Changing climatic conditions, Prabhakaran noted, also become more favourable for the spread and disease transmission potential of viruses and their vectors.

“Hot and humid conditions can both impact the disease transmission pathways, frequency of disease occurrence and severity of disease,” she explained. Ecologist Abi T Vanak added that changes in climate will also result in the shift of habitat for species, thereby introducing new vectors to some areas, or making some species more susceptible to new viruses that may have the potential to transmit to humans.

“For example, extreme rainfall and flooding in the drier parts of the country can result in outbreaks of diseases that are typically associated with the wetter parts,” Vanak, interim director, Centre for Policy Design, Ashoka Trust for Research in Ecology and the Environment (ATREE), Bangalore said.

“This is applicable to both water-borne diseases such as cholera and dysentery, as well as vector-borne diseases such as malaria, dengue, and chikungunya,” he explained.

Extreme weather events such as heatwaves can also cause high stress of animals, making them more vulnerable to disease prevalence and outbreaks of potentially zoonotic diseases, he said.

Prabhakaran’s team is involved in a collaborative research effort that aims to demonstrate the links between changing climate conditions and patterns of vector-borne diseases like dengue and malaria.