Nine tick-borne infections affect humans in the United States. Data on a national level are available for Lyme disease, Powassan encephalitis, Rocky Mountain spotted fever, Tularemia, Granulocytic ehrlichiosis (Anaplasmosis) and Human monocytic ehrlichiosis. Statistics for three diseases (Babesiosis, Relapsing fever and Colorado tick fever) are not published. The following graph compares reporting trends for tick-borne infections (Lyme disease displayed as cases/100,000 for fit). [1,2]
Note an apparent parallel increase for some diseases during 2000 to 2008, followed by a dip during 2009 to 2010. Assuming a statistical association between these data, explanations might include changes in tick populations as a whole, or trends in human-tick contact over time.
1. Berger SA. Infectious Diseases of the United States, 2012. 1089 pp, 467 graphs, 9760 references. Gideon e-books, https://www.gideononline.com/ebooks/country/infectious-diseases-of-the-united-states/
2. Gideon graph tool at https://www.gideononline.com/wp-content/uploads/Gideon-Graphs.pps