Flu Basics: What You Need to Know

Seasonal flu (influenza) information from Massachusetts General Hospital

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.

How do I know if I have flu?

The symptoms for all varieties of flu are similar. People who have the flu often feel some or all of these symptoms:

• Fever* or chills
• Cough
• Sore throat
• Nasal congestion
• Muscle or body aches
• Headache
• Fatigue (very tired)
• Vomiting and/or diarrhea (more common in children than adults)

*It’s important to note that not everyone with flu will have a fever.

How do I know if I have the flu?

If you get sick with flu-like symptoms, you should stay home and avoid contact with other people except to get medical care. Most people with the flu have mild illness and do not need medical care or antiviral drugs.

However, some people are more likely to get flu complications, including young children, people 65 and older, pregnant women and people with asthma or diabetes) and they should talk to a health care provider about whether they need to be examined if they get flu symptoms. Also, it's possible for healthy people to develop severe illness from the flu, so anyone concerned about their illness should consult a health care provider.

There are emergency warning signs. Anyone who has them should get medical care right away.

What are the emergency warning signs?

In children:

• Fast breathing or trouble breathing
• Bluish skin color
• Not drinking enough fluids
• Not waking up or not interacting
• Being so irritable that the child does not want to be held
• Flu-like symptoms improve but then return with fever and worse cough
• Fever with a rash

In adults:

• Difficulty breathing or shortness of breath
• Pain or pressure in the chest or abdomen
• Sudden dizziness
• Confusion
• Severe or persistent vomiting
• Flu–like symptoms that improve but then return with fever and worse cough

Do I need to go the emergency room if I am only a little sick?

No. The emergency room should be used for people who are very sick. You should not go to the emergency room if you are only mildly ill. If you have the emergency warning signs of severe flu sickness, you should go to the emergency room. If you get sick with flu symptoms and are at high risk of flu complications or you are concerned about your illness, call your health care provider for advice. If you go to the emergency room and you are not sick with the flu, you may catch it from people who do have the virus.

How long should I stay home if I’m sick?

CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other things you have to do and no one else can do for you. (Your fever should be gone without the use of a fever-reducing medicine, such as Tylenol^®.) You should stay home from work, school, travel, shopping, social events, and public gatherings.

What should I do while I’m sick?

Stay away from others as much as possible to keep from making them sick and get plenty of rest. If you must leave home, for example to get medical care, wear a facemask if you have one, or cover coughs and sneezes with a tissue. Wash your hands often to keep from spreading flu to others. Visit the Taking Care of a Sick Person in Your Home guide for more information.

This content is adapted from "What You Should Know for the 2017-2018 Influenza Season" from The Centers for Disease Control and Prevention (CDC).