Patient information from BMJ


Last published:Jun 23, 2020

Flu is caused by a virus. If you catch flu you'll probably feel very ill with a headache, fever, chills, and aches. But most people get better without needing any treatment.

What is flu?

Flu is an infection of your airways. It's caused by an influenza virus. The symptoms are similar to those of a cold, but a lot more severe. Flu is most common in the late autumn, winter, and early spring.

What are the symptoms?

If you have flu you may get a fever (about 100°F to 104°F), chills, a dry cough, muscle aches, a headache, and a sore throat. You will probably also feel generally unwell and very tired.

Flu can make you feel terrible for a few days but it isn't usually serious. But you should see a doctor if you get flu if and you are:

  • an older person

  • pregnant, or

  • you have a long-term medical condition, such as heart, lung, or kidney disease, or diabetes.

You should also see a doctor if you feel very ill, have difficulty breathing, or are ill for more than a few days. If you have young children and you think they might have flu, you should take them to see a doctor.

What treatments work?

Most people with flu get better on their own. Usually the best thing to do is to stay at home, rest, and drink plenty of fluids. Acetaminophen can help with aches or fever. Ibuprofen is another option.

Children can use child versions of these medicines. However, children under 16 should not take aspirin, as it can cause a rare but serious illness called Reye's syndrome, which leads to swelling in the liver and brain.

There are medications to treat flu, called antiviral drugs. But most people don't need them. Doctors usually reserve them for people who are very ill, or have a greater chance of becoming very ill from flu. These include older people, very young children, pregnant women, and people with a long-term medical condition that could make having flu more serious.

Antivirals work best if they are used within two days of the start of flu symptoms. People who take one of these medications get better about a day or two sooner than people who don't take them. These medications may also help prevent serious problems (complications), such as pneumonia.

What will happen to me?

You'll probably feel pretty sick for about one week. And you may cough and feel tired for a couple of weeks. But most people recover from flu without any problems.

For some people, having flu is more serious. They may get problems such as bronchitis or pneumonia. This is more likely to happen if you're very young, older than 65, pregnant, or have another medical problem, such as a lung disease (for example, asthma) or heart disease.

Should I get a flu vaccine?

A flu vaccine won't help if you have the flu already. But it can reduce your chance of getting the flu in the future. It's given as an injection or a nasal spray. To be protected, you need to get a new flu vaccine each year, usually in the fall.

In the United States, doctors recommend that adults and children age 6 months and older get an annual flu vaccine. If you're allergic to eggs, talk to your doctor before getting the vaccine. Eggs are used to make most flu vaccines and you could have an allergic reaction. You should also tell your doctor if you've ever had a reaction to the flu vaccine before.

A flu vaccine can't give you the flu. You might have a sore arm where the needle went in or get muscle aches or a mild fever.

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