Changing Climate, Changing Health
To understand the way climate change is going to affect our health and wellbeing, maybe we need to start looking at the smaller picture, argues Pat thomas
Earlier this year, a team of British scientists announced that they had found the key to halting the spread of malaria, a disease that kills more than a million people a year, mostly in sub-Saharan Africa. All they had to do was release genetically modified mosquitoes, incapable of passing the plasmodium parasite, which causes malaria, into the wild. The GM mossies being a bit fitter than the natural ones, would live longer and lay more eggs and eventually become the dominant species in any mosquito-friendly habitat. Problem solved. The story was important for two reasons. Firstly, because of its absurd presumptions about the safety of this endeavour. Secondly, because as our climate changes, malaria – along with most other vector-borne diseases – is set to become a worldwide problem.
That climate change will redefine what we know about health and disease is a certainty. Yet our understanding of how it will change everything remains very limited and focused on the obvious.
It’s not just that summers will be hotter or that extreme weather patterns such as hurricanes will devastate communities. It’s not even the fact that changing climate will redistribute disease-carrying insects, such as mosquitoes, making their range much wider – though these things are indisputably important.
Dramatic increases in severe weather events such as heatwaves, major storms and flooding will certainly have a dramatic effect on our health and wellbeing. And certainly it is right that governments, scientists and health officials should be thinking about the most effective way to respond to the greater number and wider scope of climate-related health crises that we could be facing.
But to really get to grips with what climate change will mean for human health, we need to be paying attention to what will happen on the micro level – the level beyond that which we can see with our everyday eyes. For years, we have lived in fear of ‘germs’ – bacteria, viruses, fungi and other parasites that can invade our bodies and cause illness.
We spend billions each year producing antibiotics to fight bacteria. For decades, we have gulped these magic bullets down by the handful – until we realised that ‘germs’ are smarter and much more adaptable than we are and have the ability to become rapidly immune to their effects. The more we attack them, the more invulnerable they become.
If antibiotics have taught us anything, it’s that bacteria love a challenge. Likewise our efforts to control influenza, both human and avian. Now, in an era of climate change, we have set a challenge to the world’s microbes that may see them evolving faster than we can envisage creative solutions to stop them.
These changes are already happening. Last year, Dutch farmers were surprised to find their animals suffering from blue tongue disease, a viral infection that attacks the blood vessels of ruminant animals, primarily sheep, causing high fever, sweating, swollen feet and, in some animals, a characteristic blue tongue.
Elsewhere in northern Europe, cows have come down with it. But what was most surprising wasn’t just that until now, the disease was largely unknown in the northern hemisphere (it is most commonly found in Africa, Asia, Australia and the Americas), but the fact that the virus infecting the Dutch animals was a totally different type from the one that is common in the South. It had successfully adapted to our climate.
Scientists in Bangladesh studying Vibrio cholerae, the bacterium that causes cholera, have found the same thing. As climate variability in that country increases, the bacterium has rapidly evolved to be less sensitive to climate changes, and thus more robust. In Central Asia, evidence suggests that the Yersinia pestis bacterium, which causes bubonic plague, favours a warmer climate. Just a 1oºC increase in spring temperatures is predicted to lead to a more than 50 per cent increase in incidence of the disease (known commonly as the Black Death), which wiped out nearly half of the European population in the mid-1300s.
In January of this year, scientists in Australia warned that climate change could create two flu seasons in southern Western Australia – a phenomenon already noted in northern parts of the country, where milder winters mean there are now two influenza seasons a year. The infections that arise are often less severe and these milder infections can mean that the body does not produce quite enough antibodies to fight off the virus completely. Result? A population with permanent sniffles.
The news from Australia came as researchers at Cardiff University warned that milder winters in the UK could also lead to colds that were less severe but lasted much longer, maybe even permanently. The Cardiff scientists envisioned a British cold season that could last from February through to November.
It may not just be the weather that is influential in creating more adaptable and powerful bugs. Some scientists speculate that rising levels of atmospheric CO2 can have a dramatic effect on the growth cycles of viruses. The theory is that CO2 is an acidic gas, and viruses in particular thrive in more acidic conditions. Some evidence suggests that the common influenza virus, as well as the less common Ebola and SARS viruses, prefers this more acidic body environment – just the kind that might arise in the blood and tissues of humans who are inhaling more CO2 with every breath.
In the same way that viruses can adapt to changing external climate, they can also adapt to the changing internal climate of bodies living in a CO2-heavy environment. Will it make them stronger and more virulent? No one knows yet, but clearly, whatever the emerging climate can throw at them, microbes will be able to hit back – with force.
Before we try to see the silver lining of how pleasant it will be to be able to sunbathe in Britain in December, and before we celebrate ‘breakthroughs’ like GM mosquitoes, perhaps we should stop to consider the fuller picture of the potential microbial monsters we have unleashed on the world through our continued selfish, irresponsible and, frankly, antisocial habit of belching out greenhouse gases.
Pat Thomas is editor of the Ecologist.
- This article appeared in the October 2007 edition of the Ecologist. Not available online.
