Why have so many dangerous viruses emerged recently?

Source: By Rishika Singh: The Indian Express

Monkeypox, coronavirus, zika, and ebola are names that have become all too familiar over the last few years. Many of these diseases were first reported in either Asia or Africa. How viruses are detected, and are any particular regions more prone to new viral outbreaks?

How are viruses discovered?

The discovery of new viruses is often linked to outbreaks of diseases. The identification of origins is not always straightforward — one obvious example is SARS-CoV-2 which caused the Covid-19 pandemic; despite research indicating with a fair degree of certainty that the outbreak started at the Huanan Seafood Market in China’s Wuhan, some experts continue to believe the theory of the virus being laboratory-grown.

Marilyn J Roossinck, Professor of Plant Pathology and Environmental Microbiology at Penn State University wrote in a recent article in The Conversation that the identification of a new viral disease involves “a combination of extensive fieldwork, thorough lab testing, and quite a bit of luck”.

Firstly, many viruses simply exist in nature without causing harm to life around them. Many that live in animals do not get detected for a long time until they come in contact with humans through animals. These are zoonotic diseases — and Covid-19, monkeypox, and ebola, as well as older diseases like the plague or rabies, are examples.

“Another problem is that people and their food animals aren’t stationary. The place where researchers find the first infected person is not necessarily close to the place where the virus first emerged,” Roossinck wrote.

The genetic information of viruses is decoded to understand their possible origins. “Most infectious disease outbreaks start with clinicians noticing unusual patterns…at this very beginning of an outbreak, the most critical task is therefore to identify a causal pathogen,” wrote the authors of a paper published in 2018 in ‘Nature Microbiology’.

So where are the most viruses found?

As per the World Health Organisation’s Disease Outbreak News that reports cases of known and unknown diseases of concern globally, from January 2021 to the present day, the majority of cases were reported in Asian and/or African countries. There was a 63 per cent increase in the number of zoonotic outbreaks in Africa between 2012 and 2022 compared to 2001 and 2011, according to another WHO analysis.

A Reuters report from 2016 cited a study published in ‘The American Naturalist’, which said that West Africa was at the highest risk for zoonotic bat viruses. The wider sub-Saharan Africa region, as well as South East Asia, was also found to be hotspots, the report said, quoting data published between 1900 and 2013.

Why are viruses being found in Asia and Africa so often?

It’s not that these regions are innately bound to produce new diseases. Multiple factors are at work here, the most obvious one being that humans in these continents have a greater chance of coming in contact with animals more often in their many densely populated regions, thus increasing the risk of the spread of diseases.

Researchers point to the dramatic, transformative change that many countries are undergoing in these regions — countries like the UK, to an extent, went through a similar experience when they underwent industrialisation in the 18th and 19th centuries and faced diseases like cholera and typhoid.

The Nature paper from 2018 said: “Increased frequency and reach of travel, changing patterns of land use, changing diets, wars and social upheaval and climate change. These factors increase interactions between humans and reservoir hosts, facilitating exposure to zoonotic viruses and spillover infections in people.”

Coming to Africa in particular, “Infections originating in animals and then jumping to humans have been happening for centuries, but the risk of mass infections and deaths had been relatively limited in Africa. Poor transport infrastructure acted as a natural barrier,” said Dr Matshidiso Moeti, WHO Regional Director for Africa, in the WHO analysis report.

The rapid growth in urbanisation and infrastructure development, as well as the clearing of biodiversity-rich areas, has led to more interactions among species in the last few decades. Poor health systems and social upheaval may also be to blame, due to which health generally becomes neglected.

Asia has its own set of contributing factors: the dense forests here and the culture of consuming wildlife — both for food and as traditional medicine. Wet markets, where live animals are packed together and displayed for sale, have particularly come under focus due to the belief that the SARS-CoV-2 virus could have jumped from multiple species kept together. Some of these factors are old to these regions, but are contributing significantly to diseases now because of the overall increase in interconnectedness and travel among people globally in the last few decades.

What is the way forward for global health agencies and experts?

Given the reasons for the spread of disease, it might feel that this trend will only grow over time — something experts have cautioned about. But the ‘One Health’ approach is also being offered as a solution by experts across the board.

The concept basically says that human health, environmental health, and animal health are all linked together, as the pandemic has shown. WHO Director-General Tedros Adhanom Ghebreyesus said in 2021: “We cannot protect human health without considering the impact of human activities that disrupt ecosystems, encroach on habitats, and further drive climate change.”

The idea states that by avoiding overexploiting any one of these domains, and timely surveillance of the health of these domains, collective health can be protected, and the spread of disease can be made less disruptive.