The flu generally takes a disproportionate toll on certain high-risk groups through secondary infections or other complications. Those who are especially at risk include:

Children (Younger than 2)

Because young children do not have as advanced of immune systems of adults, they are more likely to have more health complications from the flu virus. These complications can include pneumonia, dehydration, sinus problems, and ear infections.

Adults (65 and Older)

Similar to young children, the elderly are more at risk from serious complications from the flu due to their inability to fight off infections and viruses. The infection can also worsen long-term health problems such as heart disease, asthma, or inflammation of the brain.


Pregnancy increases the chance of serious flu-related complications to both mother and unborn child. Fever—a common symptom of the flu—should be treated immediately because of the adverse effects it can have on the child.

Weakened Immune Systems

HIV/AIDS patients and others with weakened immune systems are at greater danger of complications from a flu infection because their bodies aren’t as adequately prepared to fight off the infection.

Aspirin Therapy

Children and teens on long-term aspirin therapy are at greater risk for complications.

Certain Diseases

People with the following diseases are at greater risk for infections because of lowered immune systems, whether caused by the disease or by the treatments.

  • Diabetes
  • Lung disease
  • Heart disease
  • Kidney disease
  • Liver disease
  • Blood disease
  • Metabolic disease

People who fall into any of these categories should receive first priority with regard to yearly flu shots. They should also see a doctor immediately if they show any symptoms of the flu, as the first 48 hours after symptoms appear provide the best window for effective treatment.

Though these categories generally describe all the types of people who are at high risk for serious flu complications, there can be exceptions depending on the specific strain of flu virus.  For example, during the H1N1 flu pandemic of 2009, better known as “swine flu,” complications from H1N1 resulted in the deaths of some adults in their 20s and 30s. This was a rare occurrence; flu viruses almost never significantly harm healthy people in this age group. This suggests that this is a new, atypical strain that these bodies have not seen before. There is some belief that the old are better protected from H1N1 than younger adults because the H1N1 virus is similar to a flu virus from the 1950s, so old folks have some retained immunity that younger people do not have.