In a landmark study in 2008, Kate Jones and colleagues at the Zoological Society of London analysed emerging infectious disease (EID) events across the globe between 1940 and 2004. They showed these to be non-randomly distributed, dominated by zoonoses (diseases which can be transmitted from animals to humans) from wildlife and dependent upon socioeconomic and environmental factors.
While a majority of the 1,500 pathogens known to infect humans came from animals and an estimated 320,000 viruses can infect mammals, it is unclear which of these can jump from animals into humans and cause disease? Are we at a greater risk from apes, which share our genes, or rodents, which share our habitats? Two recent studies have addressed this.
Olival and collaborators writing recently in the journal Nature, analysed associations between 754 mammals and 586 viruses to understand what determines viral richness, diversity and zoonotic potential. Bats were found to harbour the highest numbers of zoonotic viruses and are also a major reservoir for coronaviruses. These include the SARS virus that emerged in China in 2002, spread to 27 countries and killed 774 people and the MERS coronavirus that caused 640 deaths.
Anthony and others studied coronavirus diversity in thousands of bats, rodents and monkeys from 20 countries in Central Africa, Latin America and Asia, previously identified as zoonoses ‘hotspots’. Nearly 10% of bats had coronaviruses, the diversity being highest in locations with multiple bat species, such as the Amazon rainforest. India also has an incredibly diverse bat population with 117 species and 100 sub-species, but we know little about the viruses in Indian bats and their disease potential.
Pathogen hotspot
The Indian subcontinent is a ‘hotspot’ for zoonotic, drug-resistant and vector-borne pathogens. But we know little about the key threats. Poor domestic research and lack of international collaborations in this area, the latter driven by restrictive policies on sharing clinical and research materials, are responsible.
Prof. Ian Lipkin at Columbia University, an expert on novel pathogens, has tried to work with India for many years. “Sample access is challenging,” he says. “I'm eager to help [provided] the logistics can be sorted. Let’s focus on technology transfer in emerging infectious diseases. Global public health and the people of India deserve our best efforts.”
The transmission of infectious disease requires contact, the probability increasing with population density. With 1.34 billion people, 512 million livestock and 729 million poultry, the density and rates of human–animal, animal–animal and human–human contacts are high. These increase the potential for the emergence, circulation and sustenance of new pathogens. India has also lost about 14,000 sq km of forests over 30 years. Deforestation brings wildlife into direct contact with humans and domesticated animals, increasing the risk of zoonoses. It also alters weather patterns, indirectly and unpredictably affecting zoonoses.
Missed opportunity
India presents a poor picture of One Health. There are 460 medical colleges and 46 veterinary colleges in India, but most do little or no research. The governance structure and inter-sectorial coordination is also problematic, with human, animal and environmental health controlled by different ministries, with little cross-talk. India’s National Health Policy approved recently is also a missed opportunity. It fails to even mention “zoonoses” and “emerging infectious diseases,” let alone break the silos or enable work in key EID areas.
However, as seen during the 2006 Bird Flu outbreak, various sectors in India are capable of working together. The need is to move from being reactive to proactively understanding zoonotic pathogens before they cause human disease. This will require preparedness and policy inputs. An inter-ministerial task force should prepare a policy framework that enables preparedness by strengthening inter-sectorial research on zoonoses and health systems. Such research makes economic and political sense.
Discovering the entire viral diversity is estimated to cost $6.4 billion. The cost of the 2002 SARS outbreak is pegged at $54 billion and a severe flu pandemic could cost about $3 trillion or 5% of the world economy.
Further, a new disease emerging in any part of the world is a global threat. If India aspires to be a world leader, it cannot afford to ignore its responsibility towards global health. If India can pledge and successfully implement nuclear non-proliferation, can it remain a potential threat for disease proliferation?
The writer is CEO, Wellcome Trust/DBT India Alliance, New Delhi
shahid.jameel@wellcomedbt.org
