Lyme disease remains the most commonly reported tick-transmitted disease in the U.S., accounting for more than 95% of all tick-transmitted diseases. New data suggest that the number of people diagnosed with Lyme disease each year in the U.S. is around 300,000. Most Lyme disease cases are reported from the Northeastern states and the upper Midwest.

Lyme Disease Cases in New Hampshire

In New Hampshire and Massachusetts, the blacklegged tick (aka the deer tick) which carries Lyme disease is found most often in regions within 35 miles of the coast, and along major rivers, although it occurs statewide.

In 2012, New Hampshire reported more confirmed cases of Lyme disease than any other state in the nation; it was the third highest in 2011. Since 2006, New Hampshire has been in the nation’s top five states for Lyme disease incidence. In 2012, the number of confirmed cases per 100,000 people was 76, compared to 67 in 2011. Most cases are reported from Rockingham, Hillsborough, and Strafford Counties. In most New Hampshire counties, more than 50% of the adult blacklegged ticks tested were infected with the bacteria that cause Lyme disease.

Lyme Disease Cases in Massachusetts

Lyme disease is found in all counties in Massachusetts with the highest incidence in the eastern half of the state. Regions of particularly high incidence include Plymouth, Cape Cod and the Islands, and parts of Middlesex, Essex, and southern Berkshire Counties.

In the 2012 surveillance year, the number of combined confirmed and reported cases of Lyme disease in Massachusetts increased by 19% over 2011. In 2012, there were 3,342 confirmed cases statewide. That worked out to 51 cases per 100,000 people in 2012, compared to 27 cases in 2011. Incidence rates increased in most Massachusetts counties in 2012, with the exception of Berkshire County where the incidence rate actually decreased and in Suffolk County where it remained the same as in 2011. The highest incidence rates were for children 5-9 years old and adults aged 65-69.

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