what is considered serious infections
Urinary Tract Infections (UTIs). Urinary tract infections (UTIs) are a common type of infection caused by bacteria (most often E. coli) that travel up the urethra to the bladder. A bladder infection is called cystitis. If bacterial infection spreads to the kidneys and ureters, the condition is called pyelonephritis. Cystitis is considered a lower urinary tract infection. Pyelonephritis is an upper urinary tract infection and is much more serious.