Editor's Note: This story was updated on July 13, 2017.
Although Lyme disease is the most prevalent tick-borne infection in the U.S, ticks can transmit 20 diseases, according to the CDC. Some of these -- like Rocky Mountain spotted fever, Powassan virus and ehrlichiosis -- can be fatal. And while tick populations are not on the rise, they have expanded their range to all 50 states, says Christopher Paddock, MD, of the CDC.
The blacklegged tick -- which can transmit Powassan, Lyme disease, babesiosis, and anaplasmosis, for example -- is now in almost half of all U.S. counties. CDC data show that ticks are responsible for more emerging diseases than mosquitoes -- 95% of all vector-borne diseases, Paddock says. Ticks are also believed to transmit the Bourbon virus, which is suspected in the death of a Missouri woman in June.
“But there are many billions of ticks and thousands of cases of tick disease in the U.S.,” says Paddock, who specializes in spotted and typhus fevers.
Here’s what you need to know about tick-borne illnesses.
Q. How is Rocky Mountain spotted fever transmitted, and are cases on the rise?
A. The Arizona Department of Health Services reported seven cases of the disease in the first 4 months of 2017, Paddock says. It’s most commonly transmitted by the American dog tick in the eastern United States and the brown dog tick in the West.
Although relatively rare, Native American reservations in southeast Arizona have seen epidemic levels of the disease. Between 2002 and 2014, public health officials reported more than 300 cases of Rocky Mountain spotted fever in the region, and more than 20 people have died from the disease.
Q. Why are cases on the rise?
A. A large population of free-roaming dogs carry the ticks. When humans come into contact with the dogs, the ticks bite and infect them, Paddock says. The explosion of Arizona cases has occurred in a low-income area where many people can’t afford treatments to prevent ticks for their dogs. They might also not have the resources to neuter or spay the dogs to keep down their numbers, he says.
Outside of Arizona, the disease is typically clustered in the “tick belt” that stretches from Oklahoma to North Carolina. According to the CDC, more than 3,000 cases of the disease are reported each year, most from Oklahoma, Arkansas, Missouri, Tennessee, and North Carolina.
Q. How long does a tick have to stick to you to transmit Rocky Mountain spotted fever or other infections?
A. The tick can transmit infection in 3 hours or less. For Lyme disease, it typically takes 36 to 48 hours for the tick to transmit the infection.
Q. What are symptoms of Rocky Mountain spotted fever?
A. They aren’t much different from a flu -- fever, headache, muscle aches. But within 3-10 days, a rash will spread to your torso until it becomes spotted. At that point, the disease may be doing serious damage to your organs. Some people go on to develop permanent disabilities like gangrene, learning disabilities, and problems walking, says Paddock.
Q. How is Rocky Mountain spotted fever treated?
A. Like Lyme and most other bacterial tick-borne infections, it’s treated with the antibiotic doxycycline in the first 5 days after a tick bite. About a quarter of people with the disease who are not treated with doxycycline die within 8 or 9 days, Paddock says.
“The frustrating component is that there isn’t a lot to go on in the first 3 days of the illness,” he says. As many as 40% of people who get the disease don’t report it right away. Knowing whether your area has a higher prevalence of the disease can help diagnose it more quickly.
Q. What is the Bourbon virus?
The CDC isn’t sure what spreads this virus, but believes it may be ticks or other insects. It reports a “limited number” of cases of the virus in the Midwest and South, including some that have resulted in death. Symptoms of the virus include rash, fever, nausea, body aches, tiredness, headache and vomiting. There is no cure, and antibiotics don’t work because it’s a virus. Treatment may include IV fluids and pain medications.
Q. What are seed ticks?
The phrase "seed ticks" refers to tick larvae. The larvae look like poppy seeds on your skin. Even at this young stage, they can still bite, especially if you are living in a rural area. The bites are commonly painless. The ticks can crawl up your body under clothing, and bite you in places that are hard to see.
Q. What about other tick-borne diseases?
A. Both anaplasmosis, transmitted by the blacklegged tick, and ehrlichiosis, transmitted by the lone star tick, are on the rise. The CDC first started tracking them in 1999.
The number of ehrlichiosis cases rose sharply between 2000 and 2008 -- when 961 cases were reported -- and then dropped steadily until 2010. But the numbers climbed again, reaching 1,288 in 2015. The death rate from the disease has remained about 1% since 2010. Paddock attributes the rise to better disease identification and public awareness.
Ehrlichiosis is more common in the tick belt.
Cases of anaplasmosis, a close relative of ehrlichiosis, have also climbed, rising from 2,600 in 2011 to more than 3,600 cases in 2015. The fatality rate from the disease is less than 1%, according to the CDC.
To put the numbers in perspective, about 30,000 cases of Lyme disease are reported each year.
Treatment with doxycycline within the first 5 days of infection can cure the infections.
Q. Should we be worried about the Powassan virus this year?
A. Health officials have received more reports of Powassan, but that’s probably because of heightened awareness, says Erin Staples, MD, PhD, of the CDC. “There has been evidence of the expansion of ticks, but we don’t know if the virus is spreading.”
Unlike the other tick-borne infections, Powassan is a virus. That means antibiotics don’t work to treat it. There are no antiviral drugs that seem to work against it -- and there is a high risk of long-term disability and death, Staples says.
Powassan is rare -- only 75 cases reported in the last decade -- but its numbers could rise as more people come into contact with ticks.
Q. Where are the most cases of Powassan reported?
A. Cases are concentrated in the northeast U.S. and in the Great Lakes region -- especially in Minnesota.
Infection can occur within 15 minutes of the tick attaching, Staples says. “By the time a person notices a tick, transmission may have occurred. We encourage people to do thorough tick checks.”
Q. What are the symptoms of Powassan, and are they different from other tick-borne infections?
A. Powassan strikes with fever, chills, muscle aches, and headache, and as the virus progresses, it can lead to seizures and brain swelling -- conditions that require hospitalization. Unlike other tick-borne diseases, the symptoms of Powassan do not include a rash.
Q. How do you treat the disease?
A. Mainly with supportive care -- painkillers for headache and hospitalization for people with severe illness. Some people report fatigue for a few months after the serious symptoms pass, Staples says. The disease can be fatal for people who weren’t able to recover from Powassan-caused encephalitis, Staples says. Other patients end up with long-term memory problems or even paralysis.
Q. Can Powassan affect pets, and are the symptoms in animals different than in humans?
A. The research is scanty, but some of it suggests that household pets do have the same symptoms, Staples says.
Q. How can I prevent tick bites?
A. “Prevention is a very important component in the message we try to get across. Awareness is a powerful tool for clinicians and the public regarding these diseases,” Paddock says.
Both Paddock and Staples emphasize that prevention is the only way to avoid infection:
- Limit your exposure to tall grass; walk in the center of trails. Ticks generally latch onto your foot or leg and crawl up your body, often to your head or ears. They don’t jump or fly.
- Remove leaf litter and clear tall grass and brush around your home and the edge of your yard.
- Use a 3-foot-wide barrier of wood chips or gravel between your yard and wooded areas to keep ticks from coming into your yard.
- Mow your lawn frequently.
- Keep decks, playground equipment, and patios away from trees and the edge of your yard.
- Wear insect repellent with 20% or more DEET, picaridin, or IR3535 on skin that is exposed.
- If you’ve been outside where ticks may live, do a full-body check once you get in, or examine your skin in the shower.
- If you see a tick, remove it with tweezers as close to the skin as possible, pulling it straight out. Dispose of it by flushing it down the toilet or throwing it back outside. Don’t crush it between your fingers.
- Dogs pick up ticks and bring them inside. Check your pet’s skin for ticks, and use tick collars, sprays, shampoos, and medications to prevent ticks.
- Tumble dry clothes in a dryer on high heat for 10 minutes to kill ticks on dry clothing after you come indoors.