How Climate Change Can Spread Respiratory Infection

Medical Journal of Australia - Hugo Wilcken

SCIENTISTS and policymakers worry about the economic havoc that climate change will wreak, thanks to rising sea levels, extreme weather events or desertification. But there’s been less emphasis on the effect it is already having on the spread of infectious diseases across human populations.
This is a subject dear to the heart of leading US respiratory specialist Dean Schraufnagel, a Professor of Medicine at the University of Illinois, Chicago. Professor Schraufnagel was in Australia in November 2017 to give a fascinating talk on respiratory infection and climate change at the plenary session of the Asian Pacific Society of Respirology (APSR) Congress, held in Sydney.
“It’s not a question of whether climate change will affect human health. It already has, by altering the epidemiology of climate-sensitive pathogens,” Professor Schraufnagel told MJA InSight.
“When we change the climate, we also change habitats and bring wildlife, crops, livestock and humans into contact with pathogens to which they may have had less exposure and less immunity,” he says.
As a case in point, Professor Schraufnagel points to an outbreak of respiratory disease caused by hantavirus in Panama. Hantavirus is found in the saliva, urine and faeces of rats, the population of which had increased exponentially due to an episode of warm, rainy weather.
“Climate variation had boosted the rat population, which put them in closer proximity to humans, who then picked up the virus from the rats,” Professor Schraufnagel explains.
“The way that climate change acts on the spread of infectious diseases is very complicated, and can involve the migration of wild animals, livestock or humans, and each time there’s a change in habitat, you come into contact with new vectors and situations that can lead to infection. So, as the environment changes, we’re more likely to come into contact with infectious agents.”
In an example closer to home, an Australian study looked at how fluctuating temperatures — another measure of global climate change — can affect pneumonia incidence. It found a correlation between sharp temperature drops from one day to the next and increased emergency visits for childhood pneumonia.
Fungal infection is another area where climate change can play a significant role in the incidence of respiratory diseases.
“Endemic fungi are found in the soil. There was a well documented case, in California, where there was an outbreak of coccidioidomycosis, which is transmitted by inhaling spores and can’t be transmitted from person to person. The cases developed 2 weeks after a severe dust storm, which released the spores from the soil.”
Professor Schraufnagel says risks will vary from region to region, and some regions will be at greater risk than others.
“Borderline areas will be more affected. So arid areas at risk of desertification, or low-lying areas at risk of flooding might be the ones at most risk of respiratory infection.”
He says one of the challenges of dealing with the effect of climate change on infectious diseases is its very complexity.
“If you have a cyclone or an earthquake, you know what the damage is right away. But with climate change, it’s not so straightforward, which allows for deniers and industry lobbyists. I’m from the US, so I’m particularly hard hit by the election of Donald Trump in this regard. But I’m heartened to see the rest of the world and much of the US are still trying to do something about climate. I think we need to educate the public. Doctors and scientists and the media need to get the message out.”
At the APSR Congress, Professor Schraufnagel also chaired a workshop on another controversial topic: electronic cigarettes and respiratory health. He is of the view that e-cigarettes need a tighter regulation than they’re getting now.
“Nicotine is one of the most addictive substances in use. So, I think you have to be very conservative and I’m quite opposed to these nicotine delivery devices. The exception might be if they could be used to help people stop smoking, but that should be done through regulatory agencies. It should be prescribed medicine, or if not prescribed, at least shown to be safe in clinical trials. If the makers want to claim e-cigarettes are useful for smoking cessation, fine. Just do the trials and see what happens.”
He says there has been an increasing amount of research into the harm e-cigarette vapours can do to the lungs.
“All the potential harms of combustible cigarettes are pretty much present, although in a much smaller degree, in e-cigarettes. People say the flavouring they use is safe because they’re already used in foods, but what’s safe for eating is not necessarily safe for breathing.”
He points to diacetyl, a buttery-flavoured chemical in foods like popcorn, which is safe to eat, but when inhaled by workers in food factories was found to cause a fatal bronchitis.
“There are dozens or even hundreds of flavourings used in e-cigarettes and we just don’t know how safe they are. The harm reduction argument for e-cigarettes is fundamentally faulty, because smoking is one of the most dangerous, toxic things you can do to your lungs. To say it’s better to use e-cigarettes is like saying that getting shot with a 22-calibre gun is better than getting shot with a 35-calibre gun. When actually it’s best not to get shot at all!”


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