Risk factors

Factors that may increase your risk of developing the flu or its complications include:

• Age. Seasonal influenza tends to target children 6 months to 5 years old, and adults 65 years old or older.
• Living or working conditions. People who live or work in facilities with many other residents, such as nursing homes or military barracks, are more likely to develop the flu. People who are staying in the hospital also are at higher risk.
• Weakened immune system. Cancer treatments, anti-rejection drugs, long-term use of steroids, organ transplant, blood cancer or HIV/AIDS can weaken the immune system. This can make it easier to catch the flu and may also increase the risk of developing complications.
• Chronic illnesses. Chronic conditions, including lung diseases such as asthma, diabetes, heart disease, nervous system diseases, metabolic disorders, an airway abnormality, and kidney, liver or blood disease, may increase the risk of influenza complications.
• Race. Native American people may have an increased risk of influenza complications.
• Aspirin use under age 19. People who are younger than 19 years of age and receiving long-term aspirin therapy are at risk of developing Reye's syndrome if infected with influenza.
• Pregnancy. Pregnant women are more likely to develop influenza complications, particularly in the second and third trimesters. Women are more likely to develop influenza-related complications up to two weeks after delivering their babies.
• Obesity. People with a body mass index (BMI) of 40 or more have an increased risk of flu complications.