Could a changing climate increase our risks of getting sick? According to research published earlier this summer, it’s very likely. A study by the University of Hawaii published in the peer-reviewed journal Nature Climate Change found evidence that more than half of pathogenic diseases affecting the human population are made worse by climate change.
This does not come as a surprise to many health experts, as members of the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have been describing climate change as a public health risk for years. In some cases, this is because problems like rising temperatures put more people at risk of heat illness, failing crops lead to food insecurity, and worsening air pollution can aggravate conditions like asthma and lung cancer.
But this summer’s research pointed to another reality: Infectious disease spreads more quickly in this changing climate that it did previously. Much of this has to do with milder winters, fewer frosts, earlier springs, and hotter summers. This warmer weather gives mosquitos and ticks—known for spreading disease—more time to reproduce and grow their population. When humidity leads to heavier rainfall and a greater presence of standing water, there are more places for mosquitos to breed. In places where there are droughts, the lack of water drives the mosquitos away to congregate in areas where there is more water, resulting in greater spread of disease in those non-drought areas. In fact, according to CDC data, the number of illnesses from mosquito and tick bites doubled between 2004 and 2018.
When natural disasters such as rising sea levels, forest fires, and high temperatures force wildlife to relocate, this pushes animals into closer proximity to humans, increasing the risk of transmitting rabies and other diseases.
Fungus is another source of infectious disease made worse by climate change. For example, the fungus Coccidioides, which causes Valley fever when inhaled, was once previously found in the dry hot climate of southwestern United States and Central and South America, but in recent years has spread as far as Washington state.
Then there’s the issue of the human body—it’s just not equipped to fare well in a rapidly changing climate. Temperature fluctuations, and the related stress on the body, compromise the immune system, so a person is more likely to get sick when exposed to pathogens. Poor nutrition, either because of reduced food access or because of nutrient depletion caused by carbon dioxide, means overall less healthy populations, which are less able to stave off disease.
In all, the WHO predicts that climate change and its related health effects could lead to 250,000 deaths per year as soon as 2030. While this sounds dire, health experts hope this pattern can be changed by reducing greenhouse gas emissions. Otherwise, outbreaks such as those the world has seen recently could become more frequent than once-in-a-lifetime events.
