Ehrlichiosis

Clear→ stable

Vector-borne

Current NYS Status

133 cases in 2024 — near the 5-year baseline of ~174.

2024 statewide cases: 133

Source: NYSDOH Annual Communicable Disease Report 2024 + 5-yr baseline

What is it?

Ehrlichiosis (human monocytic ehrlichiosis) is caused by Ehrlichia chaffeensis and spread by the lone star tick. In NYS, cases are reported primarily on Long Island and in the Hudson Valley. NYS had 133 cases in 2024. It is closely related to anaplasmosis and treated the same way.

How it spreads

Transmitted by the bite of infected lone star ticks. Active from April through October. Not spread person-to-person.

Symptoms

Fever, headache, muscle aches, weakness, and fatigue beginning 1–2 weeks after the bite of an infected tick. A rash is uncommon. Lab findings often include low white blood cell count, low platelets, and elevated liver enzymes.

Who is at risk?

Anyone spending time outdoors in tick-endemic areas. Older adults and immunocompromised individuals are at higher risk for serious illness. Ehrlichiosis can occasionally be fatal if untreated.

What you can do

🛡Use tick repellent (DEET, picaridin) and check for ticks after outdoor activities

🛡Remove attached ticks promptly with fine-tipped tweezers

⚕️See a provider promptly for fever after a tick bite — treatment with doxycycline is effective but should start early

Tier B — Annual report tracking

Based on NYSDOH annual communicable disease report. Threat level reflects 2024 case counts compared to the 5-year baseline.

Seasonality: tick season

This information is for general public health awareness and is not a substitute for professional medical advice, diagnosis, or treatment.