Bacterial infections cause various signs and symptoms, largely depending on the site of infection. Systemic signs and symptoms, such as fever, are also common.

Bacteria can infect virtually any site in the human body, causing a broad array of signs and symptoms. In most cases, the predominant signs and symptoms are localized to the area of the infection. As such, the signs and symptoms of bacterial infections vary depending on the affected body site. Systemic signs and symptoms also commonly occur and generally represent the effects of immune system stimulation caused by the infection. Signs and symptoms can help identify a bacterial infection but are often insufficient to make a conclusive diagnosis because viral infections and noninfectious conditions often provoke similar features.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Systemic Signs and Symptoms

Fever -- a body temperature of 101 F or higher -- frequently occurs with a bacterial infection. Substances called pyrogens produced by the bacteria or the immune system stimulate an increase in the body temperature set point, leading to a fever. Other symptoms that frequently accompany a fever include chills, shivering and teeth chattering.

Enlarged lymph nodes, more commonly known as swollen glands, might also accompany a bacterial infection. The affected nodes typically occur near the site of the infection, for example, in the neck with strep throat. Malaise -- a generalized feeling of being unwell -- also frequently occurs with illnesses caused by a bacterial infection.

Superficial Signs and Symptoms

Localized bacterial infections of the skin and soft tissues are very common 2. Given that bacteria normally inhabit the skin surface, it's not surprising that these germs can invade and cause infection with even minor cuts and scrapes. Three key signs of a bacterial skin infection include localized redness and swelling with the affected area feeling warmer than the surrounding skin. Most minor, superficial bacterial skin infections go away on their own 2. However, spread of the infection into the underlying or surrounding tissues requires antibiotic treatment.

Internal Signs and Symptoms

When bacteria invade a particular body organ or tissue, the infection causes inflammation that in turn leads to site-specific signs and symptoms. Examples of signs and symptoms of common bacterial infections by site include 2:

  • Strep throat: throat pain and difficulty swallowing
  • Pneumococcal pneumonia: wet cough and shortness of breath
  • Bacterial food poisoning: abdominal pain, diarrhea, nausea and vomiting
  • Urinary tract infection: urinary urgency and frequency, and painful urination

Warnings and Precautions

Most bacterial infections can be treated with topical or oral antibiotics. See your doctor as soon as possible if you suspect you might have a bacterial infection. Seek emergency medical care if you experience signs or symptoms that might indicate bacterial infection of the bloodstream, nervous system or a rapidly spreading soft tissue infection. These warning signs and symptoms include:

  • Lightheadedness or fainting
  • Confusion, agitation or extreme drowsiness
  • Severe headache and/or neck stiffness
  • Cold, pale or dusky skin
  • Excessive sweating
  • Rapid or pounding heart rate
  • Expanding redness or skin discoloration, or red streaks radiating from an  area of infection
  • Severe or worsening pain in an infected area of skin

Reviewed and revised by: Tina M. St. John, M.D.