The Difference Between Cold and Flu

The words "cold" and "flu" are sometimes used interchangeably when they're actually quite different. Both produce respiratory illnesses that can leave you feeling pretty lousy, but they differ in their causes, course, severity, and treatment.

The common cold is the most frequent illness in the United States, and it is also the most common reason for healthcare provider's visits. On average, American adults will have two to four colds per year, and children will get between six and 10. The CDC estimates that 5 to 20 percent of Americans come down with the flu annually. It can be a very serious infection that claims the lives of thousands of people each year.

Cold and Flu Symptoms

The symptoms of cold and flu have some things in common, but there are significant differences. The symptoms of the flu are more severe and distinct.

Cold Symptoms

Cold symptoms typically last between seven and 10 days. Symptoms start out mild and then gradually worsen over the next few days. While a cold can leave you feeling pretty miserable, it typically isn't severe enough to interfere with your day-to-day activities.

Common symptoms include:

• Congestion
• Cough
• Runny or stuffy nose
• Itchy or watery eyes
• Sore throat
• Feeling tired
• Headache
• Fever (rarely—more common in children)

If your symptoms are much different than those listed above, you probably have another illness or infection.

Flu Symptoms

Influenza symptoms often come on hard and all at once. Many people describe it as feeling like they "were hit by a truck."

Flu symptoms include:

• Fever
• Headache
• Body aches
• Extreme fatigue
• Cough
• Sore throat
• Mild congestion—stuffy or runny nose
• Vomiting and/or diarrhea (this is uncommon in adults, occurs more frequently in children)

Causes

Both the common cold and influenza are caused by viruses. They are spread through the air in droplets produced coughing and sneezing, contact with saliva, and touching contaminated surfaces.

Cold Causes

Over 200 different viruses can cause the common cold. Rhinoviruses are the type that cause most colds, but they can also be caused by coronaviruses, respiratory synctial virus (RSV), parainfluenza, and others. While you often develop immunity to each cold virus after you catch it, there is always another cold virus out there waiting to cause similar symptoms.

Flu Causes

The flu is caused by the influenza virus. There are many strains of influenza, and it frequently mutates, creating new subtypes and variants. Although there are three main types of influenza—A, B, and C—only influenza A and B cause seasonal influenza symptoms.

People of all ages can get the flu. However, those in high-risk groups are more likely to develop serious complications. These include pregnant women, older adults, children under age 5 and people with chronic medical conditions such as heart disease, asthma, or diabetes.

Diagnosis

Cold Diagnosis

Most people do not go to the healthcare provider to be diagnosed with a cold. Even if you do, it will be diagnosed based on your symptoms and physical exam, not by any specialized tests, although some tests may be run to rule out other causes for your symptoms.

Flu Diagnosis

If you think you might have the flu, seeking medical attention early may make a difference. There are tests that your healthcare provider can perform to determine if your symptoms are caused by influenza. It's especially important to recognize the symptoms that are flu-like and notify your doctor within the first 24 hours. People at high risk for complications from the flu and should be started on treatment as soon as possible to prevent serious symptoms, complications, or hospitalization. Talk to your healthcare provider before you get sick, so you will have a plan if you develop flu symptoms.

If you have severe symptoms with a cold or flu, such as trouble breathing, wheezing, uncontrollable coughing, or a high fever, you should see your healthcare provider. Also see your practitioner if you start feeling better, but then get sick again, with worse symptoms. This is a sign of a secondary infection, such as pneumonia.

Treatment

Time is the only true "cure" for cold and flu. There are medication-free ways to help yourself feel better, such as unning a humidifier, rinsing your sinuses with saline, drinking extra clear fluids, and getting extra rest.

Over-the-counter cold medicine may help relieve symptoms. Taking a pain reliever/fever reducer such as Tylenol (acetaminophen) or Motrin (ibuprofen) can treat fever and many of the aches and pains that come with the flu. Decongestants and expectorants can help with coughing and congestion for colds and flu.

For the flu, antiviral medications can shorten the duration and protect you if you are exposed to someone with the flu. These medicines are available by prescription only, so you'll have to see your healthcare provider to get them. They are also only truly effective if started within the first 48 hours of the start of your symptoms. If you wait until you are on day three or four of your illness, they are unlikely to make a difference.

Because colds and flu are viral, they cannot be treated with antibiotics. It is important to never take unnecessary antibiotics as this has led to resistant strains of bacteria that are becoming significant health problems worldwide.

The flu shot is typically available in the United States starting in August or September. It provides protection against the flu strains researchers believe are most likely to cause illness during the upcoming flu season. Still, it isn't 100 percent effective because the influenza virus mutates so frequently. While a primary goal of the flu vaccine is to keep you from getting the flu, it can also lessen the course and severity of the flu if you do catch it.

A Word From Verywell

No one is healthy all the time. Even the healthiest person gets a cold from time to time. These germs are all around us and they are impossible to avoid. However, knowing what to expect and what to do when you get sick can help you recover as quickly as possible.