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Coronavirus crisis elicits fresh look at the future of diseases, medicine and climate change

By Kate Doyle, Saturday March 28, 2020 - 09:34 EDT
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It is when something new like COVID-19 comes along that we need to worry. - ABC

As humanity branches out further across our interconnected and warming world, we are putting ourselves at risk of encountering new diseases.

Thankfully, we are getting better at fighting back.

The experts consulted for this article were unanimous: there is no indication coronavirus has been directly connected to climate change.

There is, however, a number of infectious diseases that are affected by a warming world, and the indirect consequences of climate and environmental change are far-reaching.

"There's very good evidence that bacterial food-borne infections increase in warmer times and therefore are likely to increase with climate change," said Linda Selvey from the school of public health at the University of Queensland.

Animal-borne diseases are also likely to change with the climate as the distribution of infectious species changes.

Mosquito-borne diseases like dengue and yellow fever are expected to expand into currently temperate regions as they warm.

Dr Selvey said Lyme disease (from ticks), for example, was likely to be spreading in North America because of climate change.

Human-to-human infections

But with COVID-19 going around, it is human-to-human diseases that are the focus of the world's attention.

The influenza (flu) virus, which spreads in a similar way to COVID-19, is not showing trends of either decreasing or increasing case numbers that could be ascribed to climate change, according to Dr Selvey.

, but as it is still present at similar rates in warm, tropical climates, there is no indication the overall flu rate will decline as the world warms.

Dr Selvey did say there was potential for the temporal distribution of flu to change as wealthy regions warmed and we all congregated inside with air conditioning, where flu could spread easier, leading to a summer flu peak.

Time will tell, so at the moment it is not looking like there is a direct link between respiratory diseases and climate change ... but there could be indirect relations.

Jumping the species barrier

It is common for viruses spread from human to human to cause colds and the flu, but a degree of immunity in the population, and the fact they are regular occurrences, means our healthcare system is capable of handling the caseload.

It is when something new like COVID-19 comes along that we need to worry.

These new diseases can occur when viruses cross from animals to humans, who then pass it on to others.

Some notable examples include swine flu (2009 H1N1), which is believed to have descended from a virus that infected pigs, and the 2014-16 Ebola outbreak, which is thought to be linked to bats.

It is yet to be determined from which species COVID-19 (SARS-COV-2 virus) has come to us; .

As with animal-borne diseases, changes in the climate are likely to affect the distribution of these potential cross-over species.

Take birds, another common culprit.

"When we have an avian influenza strain crossing over into the human population, that's where we're really worried about a pandemic," said Kirsty Short, a research fellow at UQ's school of chemistry and molecular biosciences.

"Those migratory patterns of birds, and how often birds come in contact with humans, is actually directly influenced by the weather.

"We are seeing those migration patterns change with climate change."

Then there is how our human distribution is changing.

"As we have climate change, we have obviously more destruction of natural spaces, deforestation and so forth," Dr Short said.

"What we see is that people are encroaching more and more upon spaces that they previously didn't inhabit."

This is a danger because it means we are coming into contact with viruses that our immune systems have never seen.

"So in that sense, the environmental destruction associated with climate change can actually lead to an increased incidence of zoonosis, or animal viruses, jumping the species barrier and crossing over into humans," Dr Short said.

On top of that, our interconnected modern world means we're probably becoming more vulnerable to infectious diseases spreading.

"We've certainly seen that with this [COVID-19] pandemic," Dr Short said.

Competition to see who wins

The good news is that we are getting better at fighting back.

"Even though climate change and all the changes that we're going through is putting additional strain on the system, we're also coming up with new and innovative ways to fight infectious diseases," Dr Short said.

There had been a dramatic increase in surveillance, detection technologies and the ability to develop vaccines, she said.

"It is a little bit of a competition to see who wins.

"The first coronavirus vaccine has already gone into human trials; that would be unheard of even 10 years ago."

There are trials using , but before you stop washing your hands, it is still likely to be at least a year (if successful) before they are ready for widespread distribution.

But that's not all

It is not as simple as saying all disease will increase or decrease with climate change.

"I think it's more that they'll be different in different areas and at different times and some infectious diseases will increase," Dr Selvey said.

"It's possible that some may decrease."

But she said there were "many, many" other ways that climate change was highly detrimental to our health.

"Infectious diseases are just one of the many ways that our changing climate is impacting on humans."


© ABC 2020

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