Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF), also known as tick-borne typhus fever, is a bacterial disease carried by ticks. It is one of the most severe tick-borne diseases in the United States. There are 250 to 1200 cases each year in the U.S. Most cases are in southeastern and south central states. RMSF is transmitted to humans and other animals through the bite of an infected tick.

In New York City, RMSF is most commonly spread by the American dog tick. Other types of ticks can spread RMSF in other parts of the country. Ticks become infected by feeding on infected animal hosts. An infected tick usually needs to be attached to an animal for several hours to transmit RMSF bacteria. Humans cannot spread of RMSF to each other.

Rocky Mountain Spotted Fever in New York City

Nationally, the disease is reported most commonly in children under 10 years of age, but in NYC the majority of patients are middle-aged. The number of cases reported in NYC has ranged from 0 to 27 per year. For more information on the number of NYC residents reported to have RMSF, visit EpiQuery.

The American dog tick can be found in all five boroughs of New York City, as well as nearly all parks and woodlands in the eastern United States. Adult dog ticks feed on people, and are most active during the spring, summer and fall. Most cases of RMSF in New York City are reported during April, May and June. However, since ticks may be active year-round, disease transmission can also occur at any time of the year.


Symptoms can include fever, headache, rash, nausea, stomach pain, muscle pain and lack of appetite.


You can prevent Rocky Mountain Spotted Fever by avoiding tick bites.

For more information on ticks and preventing tick bites, including the use of repellents and removing ticks, visit Ticks and Tick Prevention.


Doctors treat Rocky Mountain Spotted Fever with antibiotics like doxycycline. Early treatment is important because RMSF can become life-threatening.

Information for Providers

For clinical, diagnostic, and treatment information, see Zoonotic and Vector-borne Diseases: Information for Providers.

Additional Resources

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