Flu is caused by influenza viruses that infect the nose, throat, and sometimes the lungs.
When a person who has flu virus, speaks, talks or sneezes, flu viruses are carried as tiny droplets from their nose or mouth. These droplets can land in other people’s mouth and nose who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or eyes.
People with flu are most likely to spread the flu to others in the first 3-4 days after their illness begins. Some adults may be able to infect others up to 7 days after they become sick. For people with weak immune systems, the time period they are infectious can be even longer.
Influenza and Older Adults
As people age, their immune systems get weaker (this is called immunosenescence). Older adults with weak immune systems have a higher risk of getting infectious diseases like the flu. Older adults also have more severe symptoms of the flu than younger people.
The flu kills about 40,000 people a year. Almost all of them are older adults.
Complications of flu can include:
- Pneumonia of mild to severe severity
- Sinus and ear infections
- Inflammation of other vital organs such as heart, brain, muscle tissues, and sometimes multiple organs leading to multi organ failure
- Hospitalizations, need for skilled nursing facility, or nursing home stay
- Severe complications may lead to death
Also, a person with a disease like congestive heart failure, asthma, or diabetes can be at risk of becoming very sick in short time period. For example, people who have heart disease and get the flu are likely to develop complications with heart problems as a result and need hospitalization.
Last Updated October 2022