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).
• Centers for Disease Control
• EPA bug spray advice
• How to remove a tick
• How to safely clean rodent areas