Yet the risk of getting these scary-sounding diseases is small. With the right precautions, you can still enjoy spending time outdoors. And that helps fight much more common threats to your health - obesity and too little exercise.
How it's spread: Touching or breathing air particles of urine or droppings from certain types of mice or rats, especially deer mice.
Symptoms: Develop one to six weeks later and can include flulike symptoms that progress into a dry cough, headache, nausea and vomiting, then shortness of breath.
Where it occurs: Anywhere in the U.S.; recent cases were in Yosemite National Park in California.
Prevention: Keep rodents out of your home; carefully clean any nests with disinfectant or bleach and water.
How it's spread: Mosquitoes
Symptoms: Most people have none; some develop flulike symptoms; a very small percentage get neurological symptoms.
Where it occurs: Nearly all states; this year, Texas has been hardest-hit.
Prevention: Eliminate standing water that can breed mosquitoes; use insect repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus.
How it's spread: Contact with an infected fleas, rodent or cat; prairie dogs in Colorado can carry it.
Symptoms: Sudden fever, headache, chills, weakness and swollen lymph nodes.
Where it occurs: Only about half a dozen cases occur each year across the country, mostly in the Southwest.
Prevention: Avoid contact with rodents; limit brush, rock and wood piles and rodent breeding areas near the home.
How it's spread: Ticks.
Symptoms: Fever, headache, fatigue and a bulls-eye rash. Untreated, it can cause joint, heart and nervous system problems.
Where it occurs: Northeast and mid-Atlantic coastal states; North central states, mostly Wisconsin and Minnesota; the West Coast, especially northern California.
Prevention: Use bug repellents with 20 percent or more DEET; when in the woods, walk in the center of trails, avoiding brush; shower soon after coming inside and check your body, hair and clothes for ticks.
(Also helps prevent other tick-borne diseases such as ehrlichiosis, Rocky Mountain spotted fever, tularemia and babesiosis).