Bacteria can infect any area of the body. Pneumonia, meningitis, and food poisoning are just a few illnesses that may be caused by harmful bacteria. Bacteria come in three basic shapes: rod-shaped (bacilli), spherical (cocci), or helical (spirilla). Even without antibiotics, most people can fight off a bacterial infection, especially if symptoms are mild. About 70 percent of the time, symptoms of acute bacterial sinus infections go away within two weeks without antibiotics. So if you have a fever, basically it [almost always] means you have an infection," Dr Young said. But both bacteria and viruses can cause fevers and there's no specific difference between a fever caused by bacteria and one caused by viruses. Most often, BV does not cause other health problems. However, if left untreated, BV may increase your risk for: Sexually transmitted diseases (STDs) like herpes, chlamydia, gonorrhea, and HIV. Pelvic inflammatory disease where BV bacteria infect the uterus or fallopian tubes. Antibiotics do not work on viruses, such as those that cause colds, flu, bronchitis, or runny noses, even if the mucus is thick, yellow, or green. Antibiotics are only needed for treating infections caused by bacteria, but even some bacterial infections get better without antibiotics.