An example of secondary prevention of infectious disease is:

• A. Malaria chemoprophylaxis.
• B. Pneumocystis carinii pneumonia chemoprophylaxis for people with AIDS.
• C. Quarantine.
• D. Restaurant inspections.

Answer: (C)

Secondary prevention focuses on actions taken after exposure or early illness to interrupt transmission and prevent progression. Quarantine fits this idea because it separates people who may have been exposed from the healthy population, allowing time to monitor for symptoms and intervene quickly if illness develops. By limiting contact, it breaks the chain of transmission and reduces the number of new cases, which is the essence of secondary prevention in infectious disease.

The other measures target prevention before disease occurs in individuals (primary prevention) or are environmental/public health controls. Chemoprophylaxis for malaria and for Pneumocystis pneumonia aims to prevent disease in at-risk individuals, not to interrupt transmission after exposure. Restaurant inspections are about preventing outbreaks through safe food handling, an environmental health primary prevention effort.