New data from the Centers for Disease Control and Prevention (CDC) show tickborne diseases are again on the rise. In 2017, state and local health departments reported a record number of cases of tickborne disease to CDC. Cases of Lyme disease, anaplasmosis/ehrlichiosis, spotted fever rickettsiosis (including Rocky Mountain spotted fever), babesiosis, tularemia, and Powassan virus disease all increased—from 48,610 cases in 2016 to 59,349 cases in 2017.
These 2017 data capture only a fraction of the number of people with tickborne illnesses. Under-reporting of all tickborne diseases is common, so the number of people actually infected is much higher.
This increase follows an accelerating trend of tickborne diseases reported in the United States. Between 2004 and 2016, the number of reported cases of tickborne disease doubled, and researchers discovered seven new tickborne pathogens that infect people. The new data are from the Notifiable Disease Surveillance System (NNDSS). NNDSS tracks and monitors diseases of public health importance in the United States, including six reportable tickborne disease groups.
While the reason for this increase is unclear, a number of factors can affect tick numbers each year, including temperature, rainfall, humidity, and host populations such as mice and other animals. Tick densities in any year vary by region, state, and county. Numbers of reported tickborne disease cases are also affected by healthcare provider awareness, testing, and reporting practices. Finally, during any given year, people may or may not notice changes in tick populations depending on the amount of time they or their pets spend outdoors.
According to a recent CDC Vital Signs, the United States is not fully prepared to control these threats. Local and state health departments and vector control organizations face increasing demands to respond to ticks and tickborne diseases. Proven and publicly accepted methods are needed to better prevent tick bites and to control ticks and tickborne diseases.