- CBS News Staff
- (Credit: flickr/jkirkhart35)
Yale researchers have an answer. They’ve spent three years analyzing Lyme disease risk by dragging sheets of fabric through the woods to collect ticks, and have created a detailed map that shows where disease risk is highest (pictured below). The researchers hope their map can help improve prevention, diagnosis, and treatment of Lyme disease.
The map is part of a study published in the Feb. issue of the American Journal of Tropical Medicine and Hygiene. Though the areas highlighted as high-risk likely won’t surprise anyone familiar with Lyme, the research also showed where the disease is likely spreading, and it turned up some surprising information about the rate at which ticks are infected with the bacteria that causes it, researchers said.
The map shows a clear risk of Lyme across the Northeast, from Maine to northern Virginia. Researchers also identified a high-risk region in the upper Midwest, including most of Wisconsin, northern Minnesota and a small portion of northern Illinois. "Emerging risk" regions include the Illinois-Indiana border, the New York-Vermont border, southwestern Michigan and eastern North Dakota.
"The key value is identifying areas where the risk for Lyme disease is the highest, so that should alert the public and the clinicians and the public health agencies in terms of taking more precautions and potential interventions," said study author, Dr. Maria Diuk-Wasser of the Yale School of Public Health. "In areas that are low risk, a case of Lyme disease is not impossible but it’s highly unlikely, so the clinician should be considering other diagnoses."
The map is based on data collected between 2004 and 2007. Diuk-Wasser said the high risk areas likely haven’t changed, but there might be some changes in the transitional areas. The map is still useful, however, because it highlights areas where tick surveillance should be increased and because it can serve as a baseline for future research, she said.
Named after a small Connecticut town, Lyme disease is caused by Borrelia burgdorferi bacteria, which spreads to humans through bites from infected ticks. Symptoms include a bull’s-eye rash, fever, headache, and fatigue. Antibiotics easily cure most people of Lyme, but people who aren’t treated can develop serious complications like arthritis, meningitis, facial paralysis, and an irregular heart rhythm, according to the CDC.
Previous risk maps were heavily reliant on reports of human infections, but those can be misleading, according to the study, because the disease is both over- and under-diagnosed. Where someone is diagnosed is not necessarily where the disease was contracted, and ticks may live in a region long before they actually infect someone, meaning there could be a significant risk even without confirmed cases.
The study also provided new information about the infection rate among ticks, according to Diuk-Wasser. About 1 in 5 ticks collected were infected – more than researchers expected – and that percentage was fairly constant across geographic areas, she said.
The CDC counted more than 30,000 confirmed or probable cases of Lyme in 2010, the latest data available. More than 90 percent of those cases were in 12 states: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New Hampshire, New York, Pennsylvania, Virginia and Wisconsin.
This map released by the Yale School of Public Health indicates areas of the eastern U.S. where people have the highest risk of contracting Lyme disease based on data from 2004-2007.