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Amy Hunter, wtop.com

WASHINGTON - Residents of the Northeast and Mid-Atlantic region have the highest risk of contracting Lyme disease in the United States, a new study shows.

The results of the most extensive Lyme-related field study ever undertaken in the U.S. were released on Wednesday, along with a map that clearly details locations where humans have the highest risk of contraction. The study was published in the February issue of the American Journal of Tropical Medicine and Hygiene.

Lyme disease, which is carried by ticks, is one of the most rapidly emerging infectious diseases in the North America, says the Centers for Disease Control and Prevention.

The study found high infection risks confined mainly to the Northeast and Mid-Atlantic regions, and found the South to be essentially Lyme-disease free, says Dr. Maria A. Diuk-Wasser, the lead author of the study.

However, cases of the disease were reported in the South and found only to be in individuals who had traveled to an area with a high infection rate.

"We can't completely rule out the existence of Lyme disease in the South," she says. "But it appears highly unlikely.

For the study, large teams of field scientists combed through 304 sites along the East Coast and Midwest from 2004 to 2007, dragging square-meter sections of corduroy across the ground to snag the black legged tick known to be the main carrier of the disease.

The maps that emerged from the study show the highest risk of the disease in large parts of the Northeast, as far south as Maryland and northern Virginia.

Symptoms include a red rash that expands, beginning at the tick bite, which happens in about 75 percent of those affected. The rash can appear anywhere from three to 30 days after infection, but appears on average after 7 days. It continues to expand up to 12 inches and has a "bulls-eye" appearance, says the Centers for Disease Control. It is rarely painful or itchy.

Other symptoms include fatique, chills, fever, headache, muscle and joint aches and swollen lymph nodes. In some cases, the rash does not appear but other symptoms do, which has been known to delay diagnosis, doctors say.

If left untreated, Lyme disease is known to cause any number of health conditions, most notable Bell's palsy, which is loss of muscle tone on one or both sides of the face, arthritis, cognitive defects, sleep disturbance and fatigue.

Blood tests are effective in diagnosing the disease -- if done correctly, says the CDC. It is important to avoid misdiagnosis of the disease because of its lasting effects.

Ten years ago in Maryland, 688 cases of Lyme disease were diagnosed. By 2009, that number had climbed to 1,466.

In Virginia, there were 149 cases diagnosed in 2000, and 698 in 2009.

The study was a collaborative effort by researchers at Yale School of Public Health, Michigan State University, University of Illinois and University of California Irvine, along with the CDC.

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http://www.wtop.com/41/2731034/Study-DC-region-at-highest-risk-for-Lyme-disease