context: You might already know that ticks cause Lyme disease. And maybe you've heard they can give you Rocky Mountain spotted fever, too. But these critters don't stop there. In fact, they're second only to mosquitoes in spreading disease to humans. Ticks are related to spiders, so they have eight legs. They have flat, oval bodies that swell when they eat. And they feed on the blood of all kinds of animals, from birds to deer to humans. They're also very small. Even adult ticks are only about the size of an apple seed, unless they've just fed. That means they're hard to spot, which is partly why they're so good at passing along illnesses without getting caught. Mostly, it's these ticks that gives illnesses to people: American dog tick, also called a wood tick Blacklegged tick, also called a deer tick Brown dog tick Gulf Coast tick Lone star tick Rocky Mountain wood tick Western blacklegged tick You can find at least one kind of disease-carrying tick just about anywhere in the United States, though some places have more than others. And the various regions of the country have different types, which carry different diseases. For example, Lyme disease is mostly a problem in the Northeast and Upper Midwest. Ticks make their homes in wooded areas with lots of shrubs, tall grasses and weeds, and leaf litter -- all good places from which to latch on to animals walking by. They'll settle down in overgrown patches in your yard, woodpiles, and even bird feeders. It's not just the outdoorsy types who get exposed. In fact, most people with Lyme disease got their bite while playing, gardening, or doing yardwork right outside their houses. Ticks can also hitch a ride on animals, such as pets or mice, and drop off when they pass through your yard. If you live in an area with ticks, you have a chance of being bitten. Ticks spread disease by passing along bacteria, viruses, and parasites (organisms that feed off their hosts). Most of these illnesses give you the typical flulike symptoms, such as chills, fever, headache, and muscle aches. Anaplasmosis: In the Northeast and Upper Midwest, you get this illness from the blacklegged tick. On the West Coast, it's from the western blacklegged tick. It gives you the typical symptoms, and it's treated with antibiotics. Babesiosis: Another disease from the blacklegged tick in the Northeast and Upper Midwest, this time you get parasites in your red blood cells. It can be life-threatening if you are elderly, had your spleen removed, or have a weak immune system. Borrelia Mayamotoi: Once again, you get this from blacklegged ticks in the Northeast and Upper Midwest. You may get joint pain along with flulike symptoms. It's treated with antibiotics. Colorado Tick Fever: Caused by the Rocky Mountain wood tick, you can get this in Rocky Mountain states at heights of 4,000 to 10,500 feet. You may get a fever for several days, then feel fine for a while, then have a fever for a few more days. For most, it's a mild illness. Ehrlichiosis: The lone star tick in the south-central and eastern United States causes this one. You get the typical symptoms and, sometimes, a rash. It's treated with antibiotics. Heartland virus: This is a newer illness found only in Missouri and Tennessee so far. Experts think you can get it from lone star ticks but aren't totally sure. Lyme disease: Probably the most widely known disease from ticks, you get Lyme from blacklegged ticks in the Upper Midwest and Northeast and the western blacklegged tick on the West Coast. In the United States, the tick can give you two different bacteria, each of which causes Lyme disease. Early on, you may get the telltale bull's-eye rash along with flulike symptoms. If you don't treat Lyme disease, it can lead to severe problems, such as: Brain and nervous system problems Joint pain that doesn't go away Heart issues Problems with memory and thinking clearly It's usually treated with antibiotics, and the sooner you start, the better. Powassan virus: This isn't common, but you can get it from blacklegged tick and groundhog ticks in the Great Lakes region and the Northeast. It can cause memory loss, confusion, and seizures. Red meat allergy: For some people, a bite from the lone star tick -- found from Texas to New England -- causes an allergy to red meat. You may get hives, asthma, or even a severe, life-threatening reaction called anaphylaxis. Rickettsia parkeri rickettsiosis: You get this one from the Gulf Coast tick in the South and East, especially along the coast. You get a dark scab where you were bitten, and maybe a rash. It's treated with antibiotics. Rocky Mountain spotted fever: You can get RMSF from the American dog tick, Rocky Mountain wood tick, and brown dog tick. Despite the name, it's most common in the Southeast. It usually starts off with a bad headache and high fever. Most people then get a rash that starts on their ankles and wrists and spreads from there. Doctors treat it with antibiotics. For best results, you need to start meds within 5 days of when symptoms show up. If it's not treated, RMSF is life-threatening. It damages your small blood vessels, which can cause swelling in the brain, heart, and lungs. Southern tick-associated rash illness ( STARI): This comes from the lone star tick. The symptoms are a lot like Lyme disease -- joint pain and a similar rash. But where Lyme disease is caused by bacteria, experts don't know what causes STARI. Tick-borne relapsing fever: While other diseases come from hard-bodied ticks, this one is from a soft-bodied type. People have gotten it from California to Ohio, usually after sleeping in more rustic cabins or homes. Without antibiotics, you'll repeat a cycle of 3 days of fever, then 7 days without. Tularemia: You get this from a dog tick, wood tick, or lone star tick pretty much anywhere across the country. The most common symptoms are high fever and an open, painful sore where you were bitten. It can be life-threatening, but it's treatable with antibiotics. 364 D rickettsiosis: This is a newer disease found in California from the Pacific Coast tick. It causes fever and a dark scab where you were bitten.