Recurring Zoonotic Outbreaks Highlight Global Gaps in Surveillance, Vaccines, One Health Preparedness and Pandemic Response

Recent Developments:

• Recent outbreaks involving Ebola Virus Disease, Hantavirus and Nipah Virus demonstrate that zoonotic diseases are emerging with increasing frequency at the interface of humans, animals and ecosystems, posing significant global public health challenges.
• Recent Nipah Virus events in India and Bangladesh, together with international concern over Ebola and Hantavirus, have reinforced the need for stronger One Health, genomic surveillance, equitable vaccine access and coordinated global preparedness.

Understanding Zoonotic Diseases:

What are Zoonotic Diseases?

• Zoonotic diseases (Zoonoses) are infectious diseases that naturally spread between vertebrate animals and humans through direct contact, contaminated food or water, vectors or environmental exposure.
• More than 60% of known human infectious diseases and nearly 75% of emerging infectious diseases originate from animals, making zoonotic spillover a major global health concern.
• Rapid urbanisation, deforestation, climate change, wildlife trade and increased human-animal interaction have accelerated the emergence of zoonotic pathogens worldwide.

Major Zoonotic Viruses of Concern:

Ebola Virus Disease:

• Ebola Virus Disease (EVD) is a severe viral haemorrhagic fever with an average case-fatality rate of nearly 50%, although mortality varies across outbreaks.
• Human-to-human transmission occurs through direct contact with infected blood, body fluids or contaminated materials.
• Recent outbreaks in Central Africa demonstrate that armed conflict, population displacement, weak health systems, unsafe burial practices and community mistrust significantly hinder outbreak containment.
• Licensed vaccines are available only against the Zaire ebolavirus species, while vaccines for other Ebola species remain under development.

Hantavirus:

• Hantavirus is primarily transmitted through exposure to infected rodent urine, saliva or droppings and is named after the Hantaan River region of South Korea.
• Infection may cause Haemorrhagic Fever with Renal Syndrome (HFRS) or Hantavirus Pulmonary Syndrome (HPS), both of which can rapidly progress to life-threatening complications.
• Most hantaviruses do not spread between humans; however, the Andes Hantavirus strain is capable of limited person-to-person transmission.
• The MV Hondius outbreak illustrated how international travel and enclosed environments can transform a local outbreak into a multinational public health event requiring extensive contact tracing.

Nipah Virus:

• Nipah Virus (NiV) is a highly fatal zoonotic disease naturally carried by fruit bats (Pteropus species) and can cause severe respiratory illness and acute encephalitis.
• The estimated case-fatality rate ranges from 40% to 75%, depending on outbreak circumstances and healthcare capacity.
• Transmission occurs through infected animals, contaminated food products such as raw date palm sap and close human-to-human contact, particularly in healthcare settings.
• Recurrent outbreaks in India and Bangladesh indicate that the virus remains an important regional public health threat with epidemic potential.
• No licensed vaccine or specific antiviral therapy is currently available for human use against Nipah Virus.

Vaccine Preparedness and Research Pipeline:

Current Vaccine Status:

• A licensed vaccine is currently available only for one major species of the Ebola Virus, while Nipah Virus, Hantavirus and several Ebola species still lack approved human vaccines.
• The absence of reliable curative therapies makes early diagnosis, rapid isolation, infection prevention and supportive clinical care essential during outbreaks.

Stages of Vaccine Development:

• Basic research, Publicly funded universities and research laboratories identify pathogen biology, immune responses and potential vaccine targets.
• Industrial translation, Pharmaceutical manufacturers convert laboratory discoveries into vaccines through formulation, clinical trials, quality assurance, regulatory approval, large-scale production and cold-chain distribution.
• Advanced technologies, Artificial Intelligence (AI), mRNA platforms, viral vector vaccines and recombinant protein technologies have significantly accelerated vaccine design, although biological validation and regulatory evaluation remain indispensable.

Why Vaccine Development Remains Challenging:

Major Constraints:

• Unpredictable outbreaks, Sporadic disease occurrence limits the feasibility of conventional large-scale clinical trials and often requires adaptive or emergency trial designs.
• Technology barriers, Advanced vaccine platforms remain protected by patents, specialised manufacturing expertise and proprietary technologies that are not universally accessible.
• Limited commercial incentives, Pharmaceutical companies may invest less in diseases affecting smaller populations or low-income regions despite their significant public health impact.
• Regulatory complexity, Vaccine development requires extensive safety evaluation, ethical approval and post-marketing surveillance before widespread deployment.

Factors Increasing Zoonotic Spillover Risk:

Emerging Drivers:

• Deforestation, habitat fragmentation and biodiversity loss increase contact between wildlife, livestock and humans.
• Climate change alters the geographical distribution of disease vectors and wildlife reservoirs, facilitating pathogen emergence.
• Wildlife trade, intensive livestock farming and expanding urbanisation create new opportunities for cross-species transmission.
• Increased global travel and trade enable infectious diseases to spread rapidly across international borders within short periods.

One Health Approach to Zoonotic Diseases:

Concept and Significance:

• One Health recognises that human health, animal health and environmental health are closely interconnected and require integrated policy responses.
• Effective zoonotic disease control requires collaboration among public health authorities, veterinary services, wildlife experts, environmental agencies and research institutions.
• Strengthening One Health surveillance improves early detection of spillover events and enhances pandemic preparedness.

Building Future Preparedness:

Priority Measures:

• Academia-industry partnerships, Universities should provide scientific research while industry should support vaccine manufacturing, quality assurance and large-scale distribution.
• Shared-risk financing, Governments, multilateral organisations and private partners should jointly finance epidemic vaccine development through advance purchase commitments, technology transfer and regional manufacturing hubs.
• Strengthening surveillance, Integrated genomic surveillance, laboratory capacity and cross-border disease reporting systems should be expanded.
• Addressing vaccine hesitancy, Transparent risk communication, community engagement and trusted local leadership should be strengthened before public health emergencies arise.
• Strengthening international cooperation, Equitable access to diagnostics, therapeutics and vaccines should become a core objective of global health governance.

India's Preparedness Against Zoonotic Diseases:

Major Initiatives:

• Integrated Disease Surveillance Programme (IDSP) strengthens early detection and reporting of infectious disease outbreaks.
• National Centre for Disease Control (NCDC) coordinates epidemiological surveillance and outbreak response across the country.
• Indian Council of Medical Research (ICMR) supports laboratory diagnosis, pathogen research and development of indigenous diagnostic technologies.
• India has strengthened One Health coordination involving the health, animal husbandry, wildlife and environmental sectors to improve preparedness against emerging zoonotic diseases.

Way Forward:

Strategic Priorities:

• Strengthen One Health governance by integrating human, animal and environmental surveillance systems.
• Expand regional vaccine manufacturing capacity and encourage equitable technology transfer.
• Improve genomic surveillance, rapid diagnostics and emergency response infrastructure for emerging pathogens.
• Promote international collaboration in vaccine research, pathogen surveillance and equitable access to medical countermeasures.
• Build resilient public health systems capable of responding rapidly to future zoonotic outbreaks while maintaining public trust.

Value Addition for UPSC:

Important Facts for Prelims and Mains:

• Zoonosis: Disease naturally transmitted between animals and humans.
• Natural Reservoir of Nipah Virus: Fruit Bats (Pteropus species).
• Only Hantavirus with Human-to-Human Transmission: Andes Hantavirus (limited transmission).
• Licensed Human Vaccine Available: Only for Zaire Ebola Virus.
• No Licensed Human Vaccine: Nipah Virus, Hantavirus and several non-Zaire Ebola species.
• WHO Priority Pathogens: Nipah Virus is included due to its epidemic potential and absence of licensed vaccines or specific treatment.
• One Health: Integrated approach recognising the interdependence of human, animal and environmental health.
• Major Drivers of Zoonotic Spillover: Deforestation, Climate Change, Wildlife Trade, Urbanisation, Global Travel and Biodiversity Loss