Causes and Risk Factors of Influenza
Flu is caused by strains of influenza viruses that travel in the air when an infected person talks, sneezes, or coughs. These respiratory droplets can make their way into the mouths or noses of nearby people and infect healthy cells and spread. People can also become infected by touching a surface that has the virus on it and then touching their face.
The virus can affect anyone, but certain people have a higher risk of being infected:
- Children younger than 5
- Adults 65 or older
- People who are obese
- Those who live or work in place with a high density of people, such as hospitals or schools
- Native American people
- Those with chronic health conditions or weakened immune systems from illnesses such as diabetes, kidney disease, or heart disease
Getting the influenza vaccine, often called a flu shot, is one of the most important actions people can take to protect themselves from infection. The flu shot is particularly important for people who work in schools or the health care profession.
When to get a flu shot
Flu season usually runs from November through February in the Northern Hemisphere. Because it takes the vaccine a few weeks to be effective, it’s better to get it early in the season. We recommend getting the vaccine in October, though it’s still effective if you get it earlier.
What type to get
There are several types of flu vaccines, and our providers can help patients decide which one is right for them:
- Injection: Given with a needle, typically in the arm
- Nasal spray (live, attenuated influenza vaccine): May be given to non-pregnant people ages 2 through 49 who prefer a spray over needles
- High-dose vaccine: For people 65 and older
- Egg-free vaccine: For people with severe egg allergies
The vaccine can have side effects, which are usually mild and go away within a few days. These include:
- Tenderness, redness, or swelling (at the site of the shot)
- Runny nose (for the nasal spray)
- Muscle aches
How effective is the flu vaccine?
The influenza vaccine tends to frustrate people because, while it is the best way to protect against the virus, it is not 100% effective. Influenza is a respiratory virus that mutates, or changes, frequently. That’s why it requires annual vaccinations.
Every year, researchers monitor viruses worldwide and update the flu vaccine to combat what they think will be the dominant circulating strains that will cause flu that year. The predictions of these experts are pretty accurate but not perfect. Recent studies by the CDC estimate the vaccine reduces the risk of influenza by 40% to 60% in the overall population. The flu vaccine appears to be even more effective in preventing the most severe forms of flu. In a study conducted from 2012 to 2015, it was found that the flu vaccine reduced the risk of being admitted to the intensive care unit for the flu by 82%. Studies have also shown that being infected with the flu can lead to a higher risk of heart attack.
Researchers at the National Institutes of Health are hard at work developing a universal flu vaccine that would protect against multiple strains for up to 10 years. But that breakthrough could be years away. For now, UT Southwestern’s infectious disease specialists say there is no debate: The flu vaccine is the best defense against influenza.
Other ways to stay safe
In addition to getting a flu vaccine, people can protect themselves and others from the virus by:
- Washing their hands with soap often, for at least 20 seconds at a time
- Wearing a mask (and changing it if it becomes soiled from a runny nose or cough)
- Not sharing silverware, drinks, towels, or personal hygiene items
- Covering their mouth with a tissue or the inside of the elbow when they cough or sneeze
- Sanitizing high-touch surfaces, such as doorknobs, light switches, and toilet handles
- Taking precautions by not going to the office and not traveling if they do not feel well and not sending children to school if they don’t feel well
Contact your provider if you have symptoms of the flu so you can be tested and begin treatment as soon as possible.