US Had Record Number of Tick-borne Diseases in 2017

Megan Brooks

November 14, 2018

Tick-borne diseases are once again on the rise in the United States, and the reasons aren't clear, the Centers for Disease Control and Prevention (CDC) said in a news release today.

In 2017, state and local health departments reported a record number of cases of tick-borne diseases to the CDC, according to surveillance data. 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.

Table. Reported Tick-borne Diseases

  2016 2017
Lyme Disease (confirmed and probable) 36,429 42,743
Anaplasmosis/ehrlichiosis 5750 7718
Spotted fever rickettsiosis 4269 6248
Babesiosis 1910 2368
Tularemia 230 239
Powassan virus 22 33
Total 48,610 59,349

The CDC notes that the 2017 data capture "only a fraction" of the number of people with tick-borne illnesses because underreporting of all tick-borne diseases is common.

The increase noted in 2017 mirrors an accelerating trend of tick-borne diseases reported in the United States. Between 2004 and 2016, the number of reported cases of tick-borne disease doubled, and researchers discovered seven new tick-borne pathogens that infect people.

US Not Fully Prepared for the Threat

Although the reason for the increase in tick-borne disease is unclear, the CDC says several factors can affect tick numbers each year, including temperature, rainfall, humidity, and host populations, such as mice and other animals. In any year, tick densities vary by region, state, and county. Heathcare provider awareness, testing, and reporting practices can also affect numbers of reported cases of tick-borne disease.

In a Vital Signs report released in May, the CDC noted that diseases caused by mosquito, tick, and flea bites more than tripled in the United States from 2004 and 2016. The CDC concluded that the United States is not fully prepared to control these threats.

The CDC has encouraged state and local public health agencies to do the following:

  • Build and sustain public health programs that test and track germs and the mosquitoes and ticks that spread them.

  • Train vector control staff on five core competencies for conducting prevention and control activities.

  • Educate the public about how to prevent bites and control germs spread by mosquitoes, ticks, and fleas in their communities.

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