Rocky Mountain Spotted Fever
12 cases in 2024 (baseline: ~34). Low absolute count.
What is it?
Rocky Mountain Spotted Fever (RMSF) is caused by Rickettsia rickettsii, transmitted primarily by the American dog tick in the eastern US. Despite its name, it occurs across the United States. NYS had 12 cases in 2024. It is one of the most severe tick-borne diseases in the US and can be fatal within days if not treated immediately.
How it spreads
Transmitted by the bite of infected ticks, primarily the American dog tick (Dermacentor variabilis) in NYS. The tick must be attached for several hours before transmission can occur. Not spread person-to-person.
Symptoms
Sudden high fever, headache, and muscle pain beginning 2–14 days after a tick bite. A characteristic spotted rash usually appears 2–5 days after fever, starting on wrists and ankles and spreading to the trunk. The rash may be absent or appear late — do not wait for it before seeking treatment.
Who is at risk?
Anyone spending time in tick habitat. Children under 10 are at higher risk for severe disease. The case fatality rate can reach 20–25% without treatment.
What you can do
Based on NYSDOH annual communicable disease report. Threat level reflects 2024 case counts compared to the 5-year baseline.
This information is for general public health awareness and is not a substitute for professional medical advice, diagnosis, or treatment.