Actual U.S. Lyme disease cases 10 times the number reported to CDC ATLANTA, Aug. 19 (UPI) -- Each year, more than 30,000 cases of Lyme disease are reported to federal health officials, but U.S. researchers say the actual number is closer to 300,000. Dr. Paul Mead, chief of epidemiology and surveillance for the Centers for Disease Control and Prevention's Lyme disease program, said the preliminary estimates of 300,000 cases of Lyme disease were presented at the International Conference on Lyme Borreliosis and Other Tick-Borne Diseases in Boston. "We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater," Mead said in a statement. The preliminary estimate was based on findings from three ongoing CDC studies that use different methods, but all aim to define the approximate number of people afflicted with Lyme disease each year, Mead said. The first project analyzed medical claims information for about 22 million insured people annually for six years, the second project was based on a survey of clinical laboratories and the third project analyzed self-reported Lyme disease cases from a survey of the general public. Most Lyme disease cases reported to CDC via national surveillance were concentrated heavily in the Northeast and upper Midwest, with 96 percent of cases in 13 states. Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks, also called deer ticks. Typical symptoms include fever, headache, fatigue and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. The CDC recommends people prevent Lyme disease and other tick-borne diseases by: Using repellent. Checking for ticks daily. Showering soon after being outdoors. Calling your doctor if you get a fever or rash. For more information on Lyme disease, see www.cdc.gov/lyme.