What is a Secondary Infection?

An image of molluscum contagiosum on the chest. The central lesion has been scratched/picked and shows signs of irritation.. Photo © A.D.A.M.

What is a Secondary Infection?

A secondary infection can occur when a different infection, known as the primary infection, makes a person more susceptible to disease.

A primary infection can increase susceptibility to disease in several ways. It can alter the effectiveness of the immune system. It can also make it easier for the secondary infection to get into the body. The opportunistic infections associated with AIDS are a good example of the types of secondary infections that occur when a disease modifies the immune response.

Skin infections that result from scratching molloscum contagiosum or similar sores are also secondary infections. These show how one disease can make it easier for another to get into the body. The sore from the STD makes it easier for other bacteria to enter and infect the skin.

Treatment for a primary infection can also lead to secondary infections. One common example of this is how antibiotic treatment leaves women more susceptible to yeast infections. Antibiotics disrupt the normal vaginal flora. That gives yeast, which are normally present at low levels, an opportunity to overgrow.

Individuals may also experience infections at the insertion sites of IVs, catheters, and other types of treatment that leave foreign objects in the body for extended periods of time. These are not always considered to be secondary infections.

Sources:

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Fabiny A. Ask the doctor. I recently took antibiotics to treat an oral infection and as a result developed a vaginal yeast infection. Can I treat it myself, and what are the most effective options? Harv Womens Health Watch. 2014 Sep;21(13):2.

Karchmer TB, Giannetta ET, Muto CA, Strain BA, Farr BM. A randomized crossover study of silver-coated urinary catheters in hospitalized patients. Arch Intern Med. 2000 Nov 27;160(21):3294-8.

Mirani G, Williams PL, Chernoff M, Abzug MJ, Levin MJ, Seage GR 3rd, Oleske JM, Purswani MU, Hazra R, Traite S, Zimmer B, Van Dyke RB; IMPAACT P1074 Study Team. Changing Trends in Complications and Mortality Rates Among US Youth and Young Adults With HIV Infection in the Era of Combination Antiretroviral Therapy. Clin Infect Dis. 2015 Aug 12. pii: civ687.

Pasman L. The complication of coinfection. Yale J Biol Med. 2012 Mar;85(1):127-32.

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