What You Need to Know About the Flu

Fall is flu season, but it may not be obvious how bad the season will be until November or even later. Sometimes the patterns will be similar to the past season, but not always.

As a result of the COVID-19 pandemic, the proportion of people diagnosed with flu was unusually low, due to masks and other restrictions put in place by countries all over the world. Some experts think this could result in less immunity and more severe flu seasons in 2022 and the following years.[1]  Prior to COVID-19, in a given week during flu season, 2% to 5% of all visits to the doctor’s office were for flu-like illness. Most people who had to go to the hospital for flu-related reasons were aged 65 and older.

Flu is the short name for influenza. It is a virus that usually infects 5% to 20% of the population in the United States during the fall and winter. Prior to COVID-19, approximately 200,000 people in the U.S. were hospitalized with seasonal flu every year, and tens of thousands died from it. Deaths are usually from infections like pneumonia that can be triggered by the flu.

Where Does the Flu Come From, and How Can We Protect Ourselves?

The flu virus can spread from person to person, animal to animal, or animal to person. The viruses that make us sick each season are spread from person to person. Virus spread from animal to human is rare, and those who get sick usually have direct contact with the sick animal. It is very rare to catch the animal virus from another person.

The specific strains of virus that cause the seasonal flu are different every year, which is why we need to get annual flu shots instead of a one-time vaccination. Antibiotics don’t work on the flu because antibiotics kill bacteria, not viruses.

Public health experts keep a close watch on the flu viruses from previous years and ones moving through animal populations to predict which strains are likely to cause infection during flu season.

New vaccines are developed each year to protect against the expected strains. Vaccine production takes at least six months.

The Seasonal Flu Vaccine

At the time that vaccine production begins, experts are not yet certain which flu strains will be most common months later. This is why the effectiveness of flu shots varies each flu season. In past years, the seasonal vaccine has ranged in overall effectiveness from 29-48% and cut the need for doctor’s visits or hospitalization almost in half.[2] 

Some people who get the flu shot can still get sick because, although the flu shot will prevent many current flu strains, those strains can change quickly over time. Their new look can be different enough that our body can’t immediately fight it off.  Sometimes, scientists don’t notice one particular strain when they are designing the vaccine and so it isn’t included in the flu shot.

The benefits of getting a flu shot every year include preventing sickness, protecting our friends and family through herd immunity, and reducing the severity of sickness if you get the flu. Recent research has suggested that the flu vaccine may even protect against Alzheimer’s disease. For example, a study published in 2022 of almost 2 million adults ages 65 and older, found that the one million who had at least one flu shot during the next 4 years were 40% less likely to develop Alzheimer’s disease during that same four-year period, compared to similar patients who had not had any flu shots during that time. The authors suggested that this may be due to decreased brain inflammation as a result of improved immunity against the flu.[3]

To read more about the flu shot, see Should I Get the Flu Shot?

Healthy Habits for Flu Season

Worried about getting the flu? Here are recommendations from the CDC on how to stay healthy during flu season:

  1. Avoid close contact. Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
  2. Stay home when you are sick. If possible, stay home from work, school, and errands when you are sick. You will help prevent others from catching your illness.
  3. Cover your mouth and nose when coughing or sneezing. Whenever possible, cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick. If you use your hand to cover your mouth, wash your hands to prevent you from spreading the virus.
  4. Clean your hands. Washing your hands often will help protect you from germs. If soap and water are not available, use an alcohol-based hand rub.
  5. Avoid touching your eyes, nose or mouth. Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth.
  6. Practice other good health habits. Clean and disinfect frequently touched surfaces at home, work, or school, especially when someone is ill. Many common household products can kill the flu virus, such as chlorine, hydrogen peroxide, and alcohol. Antibacterial products will not kill viruses. Get plenty of sleep, be physically active, manage your stress, drink plenty of fluids, and eat plenty of fruits and vegetables.

And if you think you are getting sick with the flu, follow these tips from the CDC:

  1. Drink lots of clear liquids like water to prevent dehydration.
  2. Treat a fever with cool washcloth compresses, a lukewarm bath, or over-the-counter fever reducers.
  3. Treat a cough with a humidifier or over-the-counter cough medicines.
  4. If you are vomiting or have diarrhea, eat plain foods like crackers and drink lots of water.

If your symptoms worsen and become very severe, call your doctor.

Symptoms to Watch Out For

Most people who get the flu feel miserable for a few days. To protect yourself and others, stay home from work or school. Usually the best treatment is to get rest and drink lots of fluids. If you have a fever or a headache, take aspirin, acetaminophen, or ibuprofen (aspirin should not be taken by children or teens with flu-like symptoms).

For individuals with underlying medical conditions, very young children, and older people, the flu can result in serious illness and may be life-threatening. If a family member fits any of these categories and begins to have flu-like symptoms, you may need to visit a doctor, medical center, or hospital. He or she may be prescribed anti-viral medication such as Tamiflu, or be kept under a doctor’s close supervision. Tamiflu is only effective if started within 48 hours of feeling sick, and even if started that early, it has little benefit, speeding up recovery by just one day. Study results are contradictory regarding whether it reduces the severity of the flu, and it can have unpleasant or serious side effects.  To read more about Tamiflu, see To Tamiflu or Not to Tamiflu?

For children with the flu, watch out for dehydration (if the child refuses to drink); blue/gray lips, skin, or fingernails; rapid breathing; extreme sleepiness, irritability, or confusion. These symptoms mean the child needs immediate medical attention. Some flu viruses can cause more severe symptoms such as seizures in children.

The symptoms to watch out for in adults include chest pain, shortness of breath, sudden dizziness, and confusion. And anytime a person with the flu seems to be recovering and then takes a turn for the worse, developing a fever (or a recurrence of fever) or a more pronounced and painful cough with phlegm, he or she should get medical attention because another infection may be present.

All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.

The National Center for Health Research is a nonprofit, nonpartisan research, education, and advocacy organization that analyzes and explains the latest medical research and speaks out on policies and programs. We do not accept funding from pharmaceutical companies or medical device manufacturers. Find out how you can support us here.


  1. Influenza (flu). Centers for Disease Control and Prevention. https://www.cdc.gov/Flu/Index.htm. Published July 1, 2022. Accessed July 5, 2022. 
  2. CDC Seasonal Flu Vaccine Effectiveness Studies. Centers for Disease Control and Prevention. https://www.cdc.gov/flu/vaccines-work/effectiveness-studies.htm. Published March 11, 2022. Accessed July 21, 2022.
  3. Bukhbinder AS, Ling Y, Hasan O, et al. Risk of alzheimer’s disease following influenza vaccination: A claims-based cohort study using propensity score matching. Journal of Alzheimer’s Disease. June 2022:1-14. doi:10.3233/jad-220361