Key Facts
- Get the flu vaccine.
- Sneeze or cough into a tissue or your elbow to prevent the spread of infection.
- Wash your hands frequently and don’t rub your eyes or nose.
According to the Center for Disease Control, every year more than 300,000 people in the United States have to go to the hospital for flu-related problems. Colds are even more common, with Americans having 1 billion colds each year. Understanding what causes colds and flu and why they make us sick is an important part of protecting yourself from infections.
Myths vs. Truths
Colds and flu are caused by viruses:
True. Viruses are tiny particles too small to see. They enter your body through openings such as your nose and mouth. Once inside, viruses attack the cells in your body that normally keep you healthy. Some of the symptoms you have when you are sick, such as a stuffy nose or fever, are your body’s ways of fighting off infection.
Viruses are everywhere! You can’t stop them from spreading:
False. That’s not true. You can help stop the spread of the cold and flu if you know what to do. Cold and flu viruses spread by contact. When a sick person coughs or sneezes, virus-filled droplets float through the air. The most common way that flu viruses are spread is when someone who is sick with a cold or flu coughs or sneezes. However, since a lot of people cough or sneeze into their hands, hand-to-hand contact is another easy way to pass along the flu virus. Another way that these germs are spread is by an object. For example, if a sick person sneezes into their hand and then touches a door knob— and then a second person touches the knob, then their nose or eyes, the virus can enter the second person’s body and get them sick. Flu viruses can actually live on surfaces like door knobs, keyboards, or counters for 2-8 hours.
Colds and flu are no big deal. It doesn’t matter if I get sick:
False. Unfortunately, that isn’t the case. Students miss more than 22 million days of school every year just for colds alone. It’s true that many people with a cold or the flu will get better quickly, but others will have serious problems and may have to go to the hospital. People with conditions such as diabetes, asthma, or cystic fibrosis may get very sick from colds and flu.
The flu vaccine is the best flu protection available:
True. Although very few people will have minor side effects from the vaccine, it’s still the best way to prevent infection from the viruses that cause flu. Some people think getting a flu vaccine isn’t necessary or that it may make you sicker. Talk to your health care provider and parent(s) or guardian(s) about getting a flu vaccine.
Signs and Symptoms
How can I tell if I have a cold or the flu?
It can be very hard to tell for sure if you have a cold or the flu. Both are caused by viruses; however, the viruses are not the same. The symptoms for cold and flu are similar, but there are some important differences.
- Colds – milder symptoms; runny nose, scratchy throat, cough
- Flu – more symptoms especially fever, body aches, fatigue, and dry cough that happen suddenly
Read the table below to see a list of symptoms for colds and flu. You’ll notice that they share some symptoms, such as a stuffy nose. The biggest difference is that colds are usually mild and last a few days; flu symptoms are generally worse and last longer.
You may only have a few of these symptoms, or you may have more.
| Symptom: | Cold: | Flu: |
| How soon do symptoms appear? | Slowly | Usually suddenly |
| Fever | Rarely | X |
| Sneezing | X | Sometimes |
| Watery eyes | X | Sometimes |
| Runny nose | X | Sometimes |
| Stuffy nose | X | Sometimes |
| Headache | Rare or Mild | Moderate – Severe |
| Body aches | Mild | Moderate – Severe |
| Cough | X | Sometimes |
| Sore throat | X | Sometimes |
| Fatigue (feeling tired) | X | X |
| Nausea or vomiting | Rarely | Sometimes |
| Diarrhea (loose BM’s) | Rarely | Sometimes |
| Loss of appetite (not hungry) | Sometimes | X |
| Chills | Rarely | X |
| General weakness | Sometimes | X |
How long does a cold last?
Depending on your age, a cold usually lasts between 2 and 14 days after symptoms start. Most people feel better in 1-2 weeks.
When should I call my primary care provider?
You should call your primary care provider if you have any of the problems below:
- Having a cough for 10 days or more
- Fever more than 103ºF, or a fever of greater than 100.4 ºF with chills
- Your symptoms are getting worse (especially if you have a fever of >101°F)
- Any fever for 3 or more days
- Coughing up phlegm that is yellow or green
- Stomach pain
- Chest pain or pressure, trouble breathing, or coughing blood
- Vomiting (throwing up) especially if you can’t keep anything down
- Ear pain or fluid draining from your ears
- Dizziness that comes on suddenly
- You have diabetes, asthma, or another medical condition that gets worse
Should I stay home from school if I have a cold or the flu?
Most health care providers agree that anyone who has a fever and/or symptoms that could be contagious such as a productive cough with mucous, diarrhea, vomiting, or fatigue, should stay home. Talk to your parent(s) or guardian(s) if you don’t feel well enough to go to school. It’s important to get enough rest and stay hydrated (you’ll need to drink plenty of fluids) when you have a cold or flu. Staying home from school also stops the virus that causes colds and flu from spreading.
When can I go back to school after the cold or flu?
Many schools have their own rules about when you should return to school after being sick. The Centers for Disease Control (CDC) recommends that anyone with cough and fever stay home from school for at least 24 hours after they no longer have a fever or signs of a fever.
Our health guides are developed through a systematic, rigorous process to ensure accuracy, reliability, and trustworthiness. Written and reviewed by experienced healthcare clinicians from Boston Children's Hospital, a Harvard Medical School teaching hospital and consistently ranked as a top hospital by Newsweek and U.S. News & World Report, these guides combine clinical expertise, specialized knowledge, and evidence-based medicine. We also incorporate research and best practices from authoritative sources such as the CDC, NIH, PubMed, top medical journals, and UpToDate.com. Clinical specialists and subject matter experts review and edit each guide, reinforcing our commitment to high-quality, factual, scientifically accurate health information for young people.