(CNN) - An uncommon but potentially deadly disease is on the rise in the United States.
Rocky Mountain spotted fever is the deadliest tick-borne illness in the world, according to the US Centers for Disease Control and Prevention, though access to antibiotics has lowered fatality rates from 28% in 1944 to less than 0.5% today.
Rocky Mountain spotted fever can be spread to humans through the bite of an infected tick. The disease itself is caused by the bacterium R. rickettsii, which belongs to a genus of bacteria that cause typhus and other forms of spotted fevers. Rocky Mountain spotted fever was discovered in 1906 by Howard Ricketts, who later died of rodent-carried typhus, a related disease.
Although the majority of cases of the disease are reported in North Carolina, Tennessee, Oklahoma, Arkansas and Missouri, Rocky Mountain spotted fever can occur in virtually every US state.
The Wisconsin Department of Health Services confirmed on Tuesday the first documented death in the state due to the disease. Rebecca Osborn, a disease pathologist who investigated the Wisconsin woman's death, said that although any fatality is a concern to public health specialists, the death does not necessarily indicate increased risk of contracting the disease in Wisconsin.
The incidence of spotted fever rickettsiosis, a category that includes Rocky Mountain spotted fever, has increased from fewer than 2 cases per million people in 2000 to over 11 in 2014, according to the CDC. And vector-borne diseases, those spread by such creatures as mosquitoes, ticks and fleas, have nearly tripled since 2004, the CDC reported in May.
Vector-borne diseases account for more than 17% of all infectious diseases and cause more than 700,000 deaths annually around the globe, according to the World Health Organization.
Rocky Mountain spotted fever symptoms
Several species of ticks can spread the disease, including American dog ticks, which are found east of the Rocky Mountains and on the Pacific Coast; Rocky Mountain wood ticks, found in Rocky Mountain states; and brown dog ticks, found worldwide.
Rocky Mountain spotted fever can present at first like a number of common illnesses, with symptoms that can include fever, headache and gastrointestinal illness. Two to five days after symptoms begin, an individual might develop a rash.
According to Jo Foellmi, a public health nurse for La Crosse County, Wisconsin, the woman who recently contracted the disease was probably bitten by an American dog tick while she and her family were camping. She developed nausea, vomiting, diarrhea and a stomachache in addition to a rash, the telltale sign of the illness.
However, not all patients with the disease have a rash, and the rash can vary greatly in its presentation, making diagnosis difficult, said Dr. Daniel Sexton, a professor of medicine at the Duke University School of Medicine who specializes in infectious diseases.
To complicate matters, up to 40% of people who contract Rocky Mountain spotted fever don't remember being bitten by a tick, so it is important to monitor symptoms and tell a health provider if you have been in places where ticks are common, such as heavily wooded areas with tall grass.
The illness is especially important to look for in children, since they are five times more likely than adults to die from Rocky Mountain spotted fever, according to the CDC. Additionally, mortality rates are higher for African-Americans, males and those who live in the Rocky Mountain region for reasons that are still unknown.
Since ticks are most active in the summer, most cases of the disease are reported between May and August.
Treatment and prevention
The antibiotic doxycycline is the best treatment for Rocky Mountain spotted fever for children and adults who have been infected. Doxycycline treats all tick-borne pathogens, many of which present similarly at first, Sexton said.
Doxycycline is most effective when used in the first five days of illness.
Since there is no vaccine for Rocky Mountain spotted fever, the best way to prevent the disease is to avoid areas where ticks are common, check for ticks on your clothing or your body and use insect repellent that contains DEET.
"This is an issue of public awareness," Foellmi said, adding that people who spend time outside should check themselves, family members and pets for ticks and that hikers should stay on the trail to avoid encountering ticks.
Most ticks aren't infected with the bacterium that causes spotted fever, so a tick bite without any symptoms is not cause for concern, Sexton said.
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