Influenza A; Influenza B; Oseltamivir (Tamiflu) - flu; Zanamivir (Relenza) - flu; Vaccine - flu
The flu is an infection of the nose, throat, and lungs. It spreads easily.
This article discusses influenza types A and B. Another type of the flu is the swine flu (H1N1).
The flu is caused by an influenza virus.
Most people get the flu when they breathe in tiny airborne droplets from the coughs or sneezes of someone who has the flu. You can also catch the flu if you touch something with the virus on it, and then touch your mouth, nose, or eyes.
People often confuse colds and flu. They are different, but you might have some of the same symptoms. Most people get a cold several times a year. On the contrary, people get the flu only once every few years.
Sometimes, you can get a virus that makes you throw up or have diarrhea. Some people call this the "stomach flu." This is a misleading name because this virus is not the actual flu. The flu mostly affects your nose, throat, and lungs.
So what's the difference between cold and flu. The two words go together like salt and pepper or like New Year's and weight loss. I'm Dr. Alan Greene and I want to help you figure out what the difference is. Most people have a general idea that they are different, but when pressed have a hard time really saying what the difference is. The cold, the common cold, is something very common you usually get on average 3 or more times during a year. And it is a virus that's primarily in the nose. The cold is focused in the nose. The 3 main symptoms of a cold are sneezing, nasal stuffiness, and runny nose. All are focused in the nose. You may have other symptoms - you may have a fever of 100, 101, maybe you may have some tickling or scratchiness in the back of the throat. In fact, that may be the very first symptom - a little scratch in the back of the throat. Then after a couple days the nasal discharge tends to turn a little bit darker, greener. And then after about a week you're all the way better. But it's focused in the head, focused in the nose. With the flu you're sick all over. It's a whole body disease. It's a much more serious illness. The flu in the United States today still kills about 36,000 people a year. Mostly people who already are weak for some reason or another. But it's a serious illness. And it usually slams into you with a fever. Typically the fever is in the 102 all the way up to a 106 range. A higher fever often the first symptom and you feel sick all over. You have muscle aches, you're tired, you feel out of it, you really feel crummy. And after a couple of days the respiratory symptoms start to come too. And depending where the flu virus settles you might have some sneezing, you might have some coughing. The classic symptom is a dry, hacking kind of cough, could be wheezing, could be other things, but the cough is the most common. Then it's there also for around 7 days or so and then at the end of it you may have another peak of fatigue and a second peak of fever. But usually after about a week you'll start feeling better with most cases of the flu. Colds and flus are very, very different illnesses with a few of the same symptoms.
Flu symptoms will often start quickly. You can start to feel sick about 1 to 7 days after you come in contact with the virus. Most of the time symptoms appear within 2 to 3 days.
The flu spreads easily. It can affect a large group of people in a very short amount of time. For example, students and co-workers get sick within 2 or 3 weeks of the flu's arrival in a school or workplace.
The first symptom is a fever between 102°F (39°C) and 106°F (41°C). An adult often has a lower fever than a child.
Other common symptoms include:
- Body aches
- Flushed face
- Lack of energy
- Nausea and vomiting
The fever, aches, and pains begin to go away on days 2 through 4. But new symptoms occur, including:
- Dry cough
- Increased symptoms that affect breathing
- Runny nose (clear and watery)
- Sore throat
Most symptoms go away in 4 to 7 days. The cough and tired feeling may last for weeks. Sometimes, the fever comes back.
Some people may not feel like eating.
The flu can make asthma, breathing problems, and other long-term (chronic) illnesses and conditions worse.
Exams and Tests
Most people do not need to see a health care provider when they have flu symptoms. This is because most people are not at risk for a severe case of the flu.
If you are very sick with the flu, you may want to see your provider. People who are at high risk for flu complications may also want to see a provider if they get the flu.
When many people in an area have flu, a provider can make a diagnosis after hearing about your symptoms. No further testing is needed.
There is a test to detect the flu. It is done by swabbing the nose or throat. Most of the time, test results are available very fast. The test can help your provider prescribe the best treatment.
Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) help lower fever. Providers sometimes suggest you to use both types of medicine. DO NOT use aspirin.
A fever does not need to come all the way down to normal. Most people feel better when the temperature drops by 1 degree.
Over-the-counter cold medicines may make some of your symptoms better. Cough drops or throat sprays will help with your sore throat.
You will need a lot of rest. Drink plenty of liquids. DO NOT smoke or drink alcohol.
Most people with milder symptoms feel better in 3 to 4 days. They do not need to see a provider or take antiviral medicines.
Providers may give antiviral drugs to people who get very sick with the flu. You may need these medicines if you are more likely to have flu complications The health problems below may increase your risk of getting sicker with the flu:
- Lung disease (including asthma)
- Heart conditions (except high blood pressure)
- Kidney, liver, nerve, and muscle conditions
- Blood disorders (including sickle cell disease)
- A weakened immune system due to diseases (such as AIDS), radiation therapy, or certain medicines, including chemotherapy and corticosteroids
- Other long-term medical problem
These medicines may shorten the time you have symptoms by about 1 day. They work better if you start taking them within 2 days of your first symptoms.
Children at risk of a severe case of the flu may also need these medicines.
Millions of people in the United States get the flu each year. Most people get better within a week or two, but thousands of people with the flu develop pneumonia or a brain infection. They need to stay in the hospital. About 36,000 people in the United States die each year of problems from the flu.
Anyone at any age can have serious complications from the flu. Those at highest risk include:
- People over the age of 65
- Children younger than 2 years old
- Women who are more than 3 months pregnant
- Anyone living in a long-term care facility
- Anyone with chronic heart, lung, or kidney conditions, diabetes, or a weakened immune system
When to Contact a Medical Professional
Call your provider if you get the flu and think you are at risk for having complications.
Also, call your provider if your flu symptoms are very bad and self-treatment is not working.
You can take steps to avoid catching or spreading the flu. The best step is to get a flu vaccine.
If you have the flu:
- Stay in your apartment, dorm room, or home for at least 24 hours after your fever has gone.
- Wear a mask if you leave your room.
- Avoid sharing food, utensils, cups, or bottles.
- Use hand sanitizer often during the day and always after touching your face.
- Cover your mouth with a tissue when coughing and throw it away after use.
- Cough into your sleeve if a tissue is not available. Avoid touching your eyes, nose, and mouth.
The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months and older should receive the influenza vaccine. For the 2018-2019 season, the CDC recommends use of the flu shot (inactivated influenza vaccine or IIV) and the recombinant influenza vaccine (RIV). The nasal spray flu vaccine (live attenuated influenza vaccine, or LAIV) may be given to healthy, non-pregnant people 2 through 49 years of age.
Centers for Disease Control and Prevention website. Inactivated influenza VIS.
Centers for Disease Control and Prevention website. Live, intranasal influenza VIS.
Centers for Disease Control and Prevention website. What you should know about flu antiviral drugs.
Havers FP, Campbell AJP. Influenza viruses. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 258.
Hayden FG. Influenza. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 364.
Ison MG, Hayden FG. Antiviral agents against respiratory viruses. In: Cohen J, Powderly WG, Opal SM, eds. Infectious Diseases. 4th ed. Philadelphia, PA: Elsevier; 2017:chap 154.
Last reviewed on: 6/28/2018
Reviewed by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 10/08/2018.