May 13, 2022: The Centers for Disease Control and Prevention listed six Connecticut Counties in the High/Orange category as part of its COVID-19 Community Levels Map. Only Fairfield and New London Counties are listed in the Medium/Yellow category. Residents in these counties should wear a mask indoors in public; stay up to date with COVID-19 vaccines and get tested if they have symptoms. Additional precautions may be needed for residents who are at high risk for severe illness. Visit the CDC COVID-19 Community Levels Map for updates.


Lone Star Tick


Ehrlichiosis (formerly called human monocytic ehrlichiosis) is most commonly caused by the bacterium Ehrlichia chaffeensis, and less commonly by Ehrlichia ewingii. It is spread to people through the bite of an infected Lone Star Tick (Amblyomma americanum). The bacterium can cause severe illness in some people. Treatment is available; however if it is delayed, or there are underlying medical conditions, symptoms can become more severe. The best way to prevent Ehrlichiosis is to prevent tick bites.


About Ehrlichiosis


Information for Clinicians


Clinical Guidance (CDC)

National Surveillance Case Definition


Connecticut Provider Reporting Information

Reportable Disease Confidential Case Report, PD-23

Connecticut Laboratory Reporting Information

Reportable Laboratory Findings form, OL-15C


Directory of Clinical Testing Services provided by the State Public Health Laboratory

State Public Health Laboratory Contacts – for additional information


Tick-borne Diseases of the United States – a Reference Manual for Healthcare Providers


Connecticut Ehrlichiosis Surveillance

In 2008, the Centers for Disease Control and Prevention established a surveillance case definition for Ehrlichiosis and the Connecticut Department of Public Health (DPH) added the disease to the list of state-wide reportable diseases. During 2008-2018, only 2 cases have been reported to the DPH. Ehrlichia chaffeensis is the main cause of illness in Connecticut. Other species include Ehrlichia ewingii and Ehlichia muris.

Connecticut Annual Infectious Diseases Statistics




This page last updated 5/22/2020.