(HealthDay News) -- Urinary tract infections (UTIs) affect millions of people each year.
They mostly affect women, though researchers are not sure why, according to the U.S. National Kidney and Urologic Diseases Information Clearinghouse.
They're caused when bacteria (usually from the digestive tract) cling to the opening of the urethra and multiply.
Symptoms may include a frequent urge to urinate and a painful burning. Some people may also experience nausea or vomiting, or a general feeling of fatigue and "shakiness."
UTIs are treated with antibiotics, and symptoms usually begin to ease in one or two days.