(NewsNation) — The Centers for Disease Control and Prevention put out an alert Friday about an outbreak of Rocky Mountain Spotted Fever.

As of Friday, the CDC said, five patients have been diagnosed and hospitalized with confirmed Rocky Mountain Spotted Fever, or RMSF, since July. All five had been to the Mexican city of Tecate in the state of Baja California within two weeks of getting the illness, the CDC said, causing the agency to put out a traveling warning for the area. Four patients were under the age of 18. Three were U.S. residents and two were from Mexico.

Of those five people hospitalized, three died.

RMSF is described by the CDC as a “severe, rapidly progressive and often deadly disease” transmitted through the bit of infected ticks. Many patients do not even remember being bitten by a tick, the CDC cautions.

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Because RMSF is “endemic” in multiple northern Mexico states and areas of the southwestern U.S., the CDC says healthcare providers should consider it when diagnosing people who went there if they show symptoms of an unexplained febrile illness.

Signs and symptoms of RMSF can include low-moderate fever, headache, gastrointestinal symptoms, abdominal pain, myalgia, rash and edema around the eyes and on the back of hands. Those who develop a more advanced form of the disease can have altered mental status, coma, cerebral edema, respiratory compromise, necrosis and multiorgan system damage.

The fever can be treated using an antibiotic called Doxycycline, according to the CDC. Without it, RMSF can be fatal within days, the health organization says.

To prevent complications or even death from RMSF, the CDC recommends:

• seeking medical attention if you travel to Tecate or another city in northern Mexico and get a fever, headache or rash within two weeks of their return
• protecting against tick bites by using EPA-registered insect repellant, wearing protective clothing and treating dogs for ticks
• performing  tick checks on yourself or your children after outdoor activities, or when around dogs with ticks
• promptly removing any ticks after being outside
• learning about RMSF symptoms