Look for Lyme Disease to Skyrocket by Mid-Century

CC BY 2.0. Fritz Flohr Reynolds / Flickr

Researchers conclude that a warming climate will boost cases of Lyme disease by more than 20 percent in the next few decades.

The scary visions of climate change often take form in images of apocalyptic storms, scorched earth, and cities underwater. But there is so much more to look forward to! Like this scenario brought to us by researchers from Carnegie Mellon University and the Mayo Clinic College of Medicine and Science: "Rising temperatures are expected to boost the number of cases of Lyme disease by more than 20 percent by mid-century."

The disease is caused by Borrelia burgdorferi and delivered to us by means of blacklegged ticks, Ixodes scapularis, pictured above. Left untreated, which happens when it goes unnoticed initially, it can become chronic and debilitating.

Lyme disease is already the most common tick-borne disease in North America, and the number of cases has risen sharply over the last 10 years. The researchers say that since its progression depends on environmental factors, warmer daily temperatures may be leading to more ticks as well as a greater availability of hosts. And it will just get worse.

"A sizable increase in the incidence of cases of Lyme disease in the United States due to climate change is imminent," says Edson Severnini, assistant professor of economics and public policy at Carnegie Mellon University's Heinz College, who coauthored the study. "Our findings should alert clinicians, public health professionals, and policymakers, as well as the general public."

Since Lyme disease first started rearing its ugly head last century, reported cases in the U.S. have gone from 10,000 in 1991 to about 28,000 annually. The researchers say that there is mounting evidence that climate change can affect the incidence and prevalence of diseases like Lyme. "This is because ticks spend most of their life cycle outside the host in an environment where temperature and humidity directly affect their development, activity, survival, and host-seeking behavior," say the researchers. "In fact, the U.S. Environmental Protection Agency uses the number of cases of Lyme disease as an indicator of climate change." And here we thought it was a Chinese hoax. (OK, not really, but you know...)

The researchers came to their conclusion by looking at the effect of climatic variables on the frequency of the disease in 15 states where the most Lyme disease occurs. (Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, West Virginia, and Wisconsin account for 95 percent of the country's reported cases of the disease.) They used predictions from the U.S. National Climate Assessment that the temperature will rise 2 degrees Celsius (3.6 degrees Fahrenheit) by mid-century, based on projection averages for the period 2036 to 2065. Upon crunching all the data, they conclude that, "In this study, we have shown that a sizable increase in the incidence of LD cases in endemic areas of the United States due to climate change is imminent." They predict that the number of cases will increase by around 21 percent.

"Tick-borne diseases are an important public health concern and the incidence of these infections is increasing in the Unites States and worldwide," says study leader Igor Dumic, researcher at the Mayo Clinic College of Medicine and Science and the Mayo Clinic Health System. "Lyme disease is a classic example of the link between environmental factors and the occurrence and spread of disease."

You can read the whole study at the Canadian Journal of Infectious Diseases and Medical Microbiology. And in the meantime, remember that climate change promises a whole lot more than warmer days and rising sea levels.