Five reasons why the next pandemic could come from bats
Viruses that jump from animals to humans are the likely sources of major health threats, say scientists, and bats are the number one suspect.
- 8 June 2023
- 6 min read
- by Priya Joi
Viruses that spill over from bats to humans have caused some of the world's deadliest outbreaks. The latest COVID-19 pandemic is potentially just one example, as a virus related to coronaviruses in bats.
A new Reuters special report reveals how the onwards march of industrial development means we are constantly encroaching into bat habitats, massively increasing the risk of another global pandemic.
Widespread deforestation, mining for minerals and metals, and building roads and railways have meant that we are constantly invading bat habitats, making it much more likely that human and bats will come into contact.
Reuters has identified areas across 113 countries, on every continent except Antarctica, where human destruction of the environment is creating the perfect storm for another pandemic. Nearly 1.8 billion people lived in these jump zones in 2020, meaning that now, more than one in five people on Earth live in areas where the next pandemic could originate.
Here we describe five reasons why the spillover of deadly viruses from bats is becoming more likely, including how we could mitigate potential disaster.
1. Bats are super-incubators for viruses
Bats can host viruses that would kill most other mammals and as a result are estimated to act as reservoirs for around 72,000 viruses.
The way that bats live means they are the perfect species to allow viruses to multiply.
They often roost close together with other bat species, meaning that the viruses can spread and evolve, and as bats fly hundreds of kilometres hunting for food, they can spread those viruses far and wide.
2. We're seeing increases in bat-borne viruses like Ebola, Marburg and Nipah virus
Even before COVID-19, viruses carried by bats, such as Ebola, Marburg, SARS, Hendra and Nipah, together have triggered more than 90 outbreaks, infecting about 44,000 people and killing more than 16,000. COVID-19 alone has killed nearly seven million, which is a conservative estimate, as the real number is likely to much higher.
Nipah alone, which can kill as many as three in four people infected, has surfaced three times in India and Bangladesh since 2018.
Not only do many of these bat-borne diseases cause fatal symptoms such as brain haemorrhage and organ failure, there are few treatments or vaccines. There is an Ebola vaccine available to all countries in case of emergency as part of a Gavi-funded stockpile, but Nipah and Marburg vaccines are still being tested.
3. There's been an increase in virus 'jump zones'
Bats scatter viruses in their saliva, urine, blood and excrement. These can then infect people either directly when they come into contact with these substances, or via an animal that gets infected.
However, unlike mosquitoes or other insects that can spread disease to people because they are deliberately looking for warm-blooded humans to bite, bats don't seek us out. They control insect populations, pollinate plants and generally avoid humans. If not for human activity, we would be unlikely to be infected.
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But over the past few decades, widespread deforestation, mining for minerals and metals, and building roads and railways have meant that we are constantly invading bat habitats, making it much more likely that human and bats will come into contact. Unlike some animals that would be driven out if their habitat was destroyed, bats are incredibly adaptive and can inhabit human habitats when their own are lost.
This means that there are increasingly more 'jump zones' or areas where the viruses that bats harbour can jump to humans.
"You can't pinpoint risk – this pathogen and this location and this time," Barbara Han, a disease ecologist at the Cary Institute of Ecosystem Studies in New York told Reuters. But what we can do, she says, "is show that the risk is not equally distributed. It's clumped."
4. Some of the world's most populous countries are at highest risk of spillover
Countries that are densely populated and that are pursuing industrial development at breakneck speed are likely to be hotspots for virus spillover.
In China, where the virus that caused the COVID-19 pandemic originated, the China-Laos Railway is clearing 422km of forest that houses dozens of species of bat, some of which host viruses similar to SARS-CoV-2.
However, while many look expectantly to South-East Asia for a potential spillover event, across the other side of the planet in Brazil, vast swathes of the Amazon rainforest are being cleared by loggers to plant soy and cocoa. Brazil houses the third largest number of bat species in the world, and it also has more areas of high risk than anywhere else on the planet, according to the Reuters report. It has 1.5 million square kilometres of land with "prime conditions for zoonotic spillover", the report says.
In West Africa, international mining companies are stripping back the earth and the trees on it to hunt for gold, iron ore and other minerals. At the same time, Ebola and Marburg outbreaks have surfaced in the region.
In India, nearly half a billion people live in 'jump zones', and rapid industrial development in the southern state of Kerala is already bringing Nipah-carrying bats into contact with people. Now, the fear is that the virus will mutate and an even more transmissible strain will emerge.
"I'd say, even more likely, is that it's out there already," Raina Plowright, an expert on bat viruses and spillover events at Cornell University told Reuters. "The more that we pressure these environments, the more likely these events are going to happen."
5. Development doesn't need to stop, but it does need to become more considered
Trying to halt development would be futile. So, just as activities that affect the environment must now analyse and mitigate potential effects on climate change, scientists are urgently calling for mining, logging and transport sectors to consider whether their actions could trigger colossal health emergencies.
Acknowledging the risks is the first step, but this must be followed up with funding to reduce these risks – the World Bank and partners estimate this may require US$ 10 billion, which although a steep cost is nothing compared to the loss of GDP and shock to the economy that a global pandemic brings.
Health authorities need to provide risk assessments before any activities that disturb bat habitats can be taken out.
Scientists need to continue to work on understanding bats and their behaviour when living close to people as knowledge is power. As Etien Koua, epidemic intelligence manager for Africa at the World Health Organization told Reuters, "Identifying hotspots and creating models to predict what might happen would actually help governments a lot."
