Climate change could spur a 92 per cent increase in new cases of Lyme disease in the US by the end of the century, even if the world manages to limit warming to the commitments of the Paris climate deal.
The number of people in the US being infected , and there is no human vaccine for the disease, which can lead to lifelong health problems if not treated early. So far, the evidence for climate change’s influence on the ticks that infect humans with Lyme disease has been unclear.
Now, Erin Mordecai Stanford University in California and her colleagues have looked at past temperature and rainfall in the US to estimate their impact on Lyme disease cases in the US between 2000 and 2017. The team controlled for other possible drivers, including changes in forest cover and public awareness of tick-borne disease, as measured by online interest through Google Trends.
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The results were used to model what could happen in the future, and suggested that even if temperature rises are held to 1.8°C, below the 2°C goal of Paris, annual Lyme disease cases will jump by an extra 34,183 by 2100, a 92 per cent increase on levels seen in the last decade. Numbers are expected to significantly climb much earlier – 27,630 extra cases are expected by 2050.
“These results indicate that substantial future increases in US Lyme disease burden are likely,” the team writes.
Worryingly, the team says the results are likely to be conservative because they assume no human population growth. When that is factored in, the number of extra future cases nearly doubles.
Richard Ostfeld at the Cary Institute of Ecosystem Studies in Millbrook, New York, says the study largely backs up earlier research suggesting that climate change will make Lyme disease incidence worse in the US. “The methods seem credible, and the effort to control for non-climatic variables – such as public awareness, land use change – is laudable,” he says.
There are two important caveats, he says. One is that the disease data the team used has been followed by , which could make the number of future cases much worse – around 10 times higher nationally.
The other is that modelling doesn’t consider how people’s behaviour may change as a result of climate change, such as how much time we spend outdoors and during which season, both of which are key to tick exposure. If how we behave proves a key driver of Lyme disease infections in people, public education could reduce the number of future cases, he says.
Reference:bioRxiv, DOI:
