Is South Asia Becoming Zoonotic Diseases Hub?

Smithu Ghising/Dikshya Awasthi

Nepal has stepped up health surveillance following confirmed cases of the Nipah virus in India’s West Bengal, renewing concerns about the growing risk of zoonotic diseases in South Asia.

While Nipah virus infections remain rare, public health experts say the outbreak highlights a wider and increasingly frequent global trend, viruses spilling over from animals to humans as environmental and climate pressures intensify.

Nipah virus is a highly contagious zoonotic disease carried naturally by fruit bats.

Humans can contract the virus through contact with infected animals, contaminated food sources, or, in some cases, direct human-to-human transmission.

With a fatality rate that can exceed 40 percent, outbreaks often trigger swift public health alerts across the region.

Although Nepal has not reported any cases so far, health authorities note that infectious diseases do not recognize borders.

Shared ecosystems, open borders, and dense populations across South Asia mean regional outbreaks pose indirect risks to neighboring countries.

Why Are Animal-to-Human Viral Spillovers and Spillbacks Increasing?

For scientists, Nipah is not an isolated health event but part of a broader pattern of emerging infectious diseases.

South and Southeast Asia have witnessed multiple outbreaks in recent decades, including SARS, MERS, avian influenza, dengue, and other viral infections.

According to global health research, more than 70 percent of emerging infectious diseases originate in animals.

These spillovers occur most frequently in areas where human settlements overlap with wildlife habitats, allowing viruses to cross species barriers.

Health experts note that viral transmission is no longer a one-way process, with increasing evidence of spillback, where infections pass from humans back into animal populations.

Experts point to rapid environmental changes as a major contributing factor.

Deforestation, urban expansion, intensive agriculture, and infrastructure development are bringing humans, livestock, and wildlife into closer contact than ever before.

This proximity increases the likelihood of viruses jumping from animals to people – a process known as zoonotic spillover, and vice-versa.

Climate Change as a Risk Multiplier

Dr Santosh Dulal, a public health expert working within the One Health framework – which integrates human, animal, and environmental health – says climate change is intensifying these risks.

“Climate change doesn’t create viruses, but it amplifies the risk of spillovers,” Dr Dulal explains. “Rising temperatures, unpredictable rainfall, and extreme weather events stress ecosystems, alter wildlife migration patterns, and push animals closer to human populations.”

In South Asia, these climate pressures intersect with deforestation and rapid urban growth. “In densely populated, forest-dependent regions, environmental disruption creates conditions where viral outbreaks can occur more frequently than in previous decades,” Dr Dulal adds.

Environmental Disruption and Emerging Diseases

Scientific studies increasingly show that environmental degradation plays a central role in reshaping how diseases emerge and spread.

As natural habitats shrink, wildlife is forced into agricultural areas and urban fringes, increasing contact with people and domestic animals.

These newly formed interfaces provide pathways for viruses that once circulated quietly in nature to enter human populations.

In some cases, viruses can also move from humans back into animal populations, further complicating disease control and surveillance efforts.

Why Understanding the Links Matters

Health experts emphasize that recognizing the connection between environmental change, climate variability, and public health is critical – not to create alarm, but to guide prevention strategies.

“The pattern of emerging diseases in South and Southeast Asia shows that environmental change and urban growth are reshaping disease dynamics,” Dr Dulal says. “Understanding these links allows policymakers to rethink development, land use, and environmental stewardship.”

As climate change accelerates, experts warn that human health and environmental health can no longer be treated as separate issues.

The rise in viral outbreaks serves as a reminder that disruptions to nature ultimately have direct consequences for human societies.

In a region where borders are porous and ecosystems are shared, the question is no longer whether outbreaks will occur, but whether societies are prepared to address the environmental conditions that allow them to emerge.