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Secondary infections

A secondary infection is an infection that occurs during or after treatment for another infection. It may be caused by the first treatment or by changes in the body or immune system that allow a second infection that is a secondary infection.

Two examples of a secondary infection are:

  • A vaginal yeast infection after taking antibiotics to treat an infection caused by bacteria
  • Pneumonia caused by bacteria or fungi after having an upper respiratory infection (like a cold) that was caused by a virus

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References

Ison MG, Lee N. Influenza. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 332.

Review Date 8/5/2025

Updated by: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.