Cause and Risk Factors for Influenza

The flu results from infection with an influenza virus. In most cases, people infected with the flu recover without medical treatment within 2 weeks.

Patients who have

  • heart, lung (e.g., asthma), or kidney problems;
  • diabetes;
  • cancer;
  • HIV/AIDS; or
  • other chronic conditions
have a higher risk for developing complications (e.g., pneumonia) from the flu. Young children under 2 years of age and people over the age of 65 also are at increased risk.

Other people who are at increased risk for developing flu complications include the following:

  • Children who are on long-term aspirin therapy
  • Patients who have medical conditions that can compromise breathing (e.g., spinal cord injury, seizure disorders, nerve or muscle disease, brain injury)
  • Patients who live in a long-term care facility (e.g., nursing home) or who were hospitalized during the previous year
  • Women who are pregnant during flu season

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 01 Aug 2007

Last Modified: 22 Sep 2015