Spatial distribution and variation analysis of Lyme disease in the Northeastern United States

Lyme disease is a tick-borne zoonosis caused by the spirochete bacterium which is usually transmitted through the bite of infected ticks. Lyme disease in humans has become the most prevalent vector borne disease in the U.S. where more than 25,000 new cases are reported yearly. It is important to expose the distribution variation pattern and developing trend of the disease in the area for prediction and control. Based on the data from the Centers for Disease Control and Prevention (CDC), we identified the counties with high incidence, and tracked the scope and direction of Lyme disease over the past twenty years in the northeastern U.S. The analysis on four consecutive periods (1992-1996, 1997-2001, 2002-2006, and 2007-2011) shows a continuous upward trend since 1992 and the number of new Lyme disease cases occurred from 2007 to 2011 is twice as high as the number from 1992 to 1996. Furthermore, there is a substantial increase in the number of counties with high cumulative incidence (CI >50). More than half counties in northeastern U.S. have high incidence in the period of 2007-2011 and the infected scope of Lyme disease shows a continuous developing trend in the northeastern U.S. The spatiotemporal patterns with high-risk cluster of Lyme disease have expanded from the east of Delaware, New Jersey, and Connecticut State to all directions on the continent over the past two decades.