More than 2,200 cases of Lyme disease were reported in Maryland last year, almost double the number in 2006 and a record for the state.
Although the case reports won't be verified and totaled before April, "the raw numbers are up substantially in 2007. ... The doubling is probably going to be confirmed," said John P. Krick, director of the Office of Epidemiology and Disease Control Programs at the Maryland Department of Health and Mental Hygiene.
Reports of the tick-borne disease have been climbing for years in Maryland and across the United States. Experts say some of that growth probably results from more aggressive reporting by doctors and public health authorities.
"My guess is that it has much more to do with awareness, and the time and energy devoted to investigating what might be going on with patients in Maryland," Krick said. "A lot of things need to be spiffied up to make our reporting better."
The latest data from the U.S. Centers for Disease Control and Prevention show that Lyme disease reports statewide jumped from about 700 annually in the first four years of this decade to about 1,200 cases each in 2005 and 2006. There were 2,235 cases in 2007 through Dec. 15.
The sharpest increases in recent years have occurred in Anne Arundel, Baltimore, Carroll and Montgomery counties.
In one example of how changes in reporting can affect counts, Baltimore County reported two cases in 2006 and none in 2005. After the county Health Department received additional funds for Lyme disease surveillance, it reported 256 cases last year.
The CDC has reported more than 20,000 cases of Lyme disease annually across the United States in recent years, up from fewer than 10,000 a year in the early 1990s. Lyme disease advocacy groups believe the numbers are higher because the disease is often misdiagnosed.
Maryland is tied for 10th place among the 50 states, with 22.2 cases per 100,000 population in 2006. Delaware and Connecticut had the highest incidence, at 56 and 51 cases respectively.
Colorado, Montana and Hawaii had the lowest incidence of the illness.
Lyme disease is caused by bacteria called Borrelia burgdorferi, which are transmitted through bites by the black-legged tick, Ixodes scapularis. The tick's primary host is the white-footed mouse, but at times in its life cycle it will bite deer and humans.
Symptoms appear within a month of the bite. They can include chills, fever, headache, fatigue, a stiff neck, joint pain, swollen lymph nodes and a rash, often in a telltale bulls-eye shape.
Lyme disease is usually curable with antibiotics if treated early. Without treatment, it can progress to arthritis, meningitis, nerve and heart damage, and other chronic problems.
The Associated Press contributed to this article.