Influenza, or the flu, and the common cold can be tricky to tell apart. Both are respiratory illnesses caused by viruses, and they share many symptoms.
Since colds and the flu are caused by viruses, rather than bacteria, antibiotics are not an effective treatment option.
Signs and Symptoms of Cold and Flu
Both the flu and colds affect the respiratory system, though flu symptoms are typically more severe than those of the common cold.
“There are many different viruses that can cause a cold, but most of these viruses cause very similar cold symptoms,” says Aaron E. Glatt, MD, chief of infectious diseases at South Nassau Communities Hospital in Oceanside, New York.
Symptoms that the common cold and flu share may include:
- body aches
- sore throat
- nasal congestion
"Run-of-the-mill colds usually make you feel lousy but should not interfere with daily activities," says Stephen Russell, MD, an associate professor of medicine at the University of Alabama in Birmingham.
Learn More About Cold and Flu Signs and Symptoms
Causes and Risk Factors of Cold and Flu
The flu is caused by influenza viruses, but many distinct viruses (most commonly rhinoviruses) can cause a cold.
Certain populations are more susceptible to getting a cold or the flu, including the very young, older adults, and people with a compromised immune system.
Factors that can increase your risk of becoming infected include:
Weakened Immune System
Women in their second or third trimester are particularly susceptible to complications from the flu. “We’re not exactly sure why, but there has always been a question of whether or not the immune system changes during pregnancy,” says Laura Riley, MD, the chair of obstetrics and gynecology at Weill Cornell Medicine and obstetrician-gynecologist in chief at NewYork-Presbyterian Hospital in New York City.
RELATED: 8 Ways to Keep Your Immune System Healthy
What Types of Flu Are There?
Duration of Cold and Flu
The duration of a cold or the flu varies depending on the virus involved and your immune system’s ability to fight off infection. That’s why the very young, the elderly, and people with chronic illnesses are most susceptible to viral infections and possible complications.
“The best weapon we have is our own immune system,” says Donald W. Novey, MD, a family and integrative medicine specialist in Poulsbo, Washington. Good nutrition, adequate sleep and exercise, and low levels of stress can bolster the immune system. “A failure on any one of these four points can weaken the immune system and either prolong an existing cold or lead to more frequent ones,” Dr. Novey says.
Cold symptoms typically subside within 7 to 10 days, while the flu typically lasts three to seven days with severe symptoms subsiding after a few days. But some symptoms, like fatigue and cough, can linger for weeks.
RELATED: How Long Does a Cold or Flu Last?
Complications of Cold and Flu
Most common colds are not severe, but they can worsen or lead to health complications.
“Enteroviruses that are often the culprits in the common cold can cause brain lining inflammation that causes severe headaches, difficulty looking at bright lights, neck stiffness, high fever, and confusion,” says Cameron Wolfe, MBBS, an infectious-disease specialist at Duke University School of Medicine in Durham, North Carolina.
If cold or flu symptoms persist or worsen, the patient may have a secondary or bacterial infection. That can lead to sinus or ear infections, bronchitis, and pneumonia. The flu can also worsen preexisting medical problems, such as triggering asthma attacks in people with asthma.
Learn More About Complications of Cold and Flu
Research and Statistics: Who Gets Cold and Flu?
Related Conditions of Cold and Flu
- Ear infections
- Sinus infections
- Strep throat
What Is the Flu Season Like Where You Live?
- The Everyday Health flu map predicts flu severity county by county across the United States so you can plan ahead and take precautions to avoid the flu — both at home and in places where you plan to travel.
- By entering your ZIP code, you can find out what influenza conditions may be like in your county in the weeks ahead.
Resources We Love
Favorite Organizations for Essential Information
American College of Obstetricians and Gynecologists (ACOG)
ACOG’s Immunization for Women program provides patients, including those who are pregnant, with up-to-date recommendations and guidelines on treating seasonal influenza and other vaccine-preventable diseases. This trusted source also provides a searchable ob-gyn directory.
Centers for Disease Control and Prevention (CDC)
The CDC’s website presents weekly updates on flu activity nationwide. The site details how the flu may be spreading in each state and which strains of the virus are most prominent. It also contains useful guidelines for the most current treatments and vaccinations.
National Foundation for Infectious Diseases (NFID)
Founded in 1973, the NFID is a nonprofit dedicated to educating the public and healthcare providers about infectious diseases. Its influenza web page provides basic information about the flu and links to sections about influenza in vulnerable segments of the population, such as children and older adults.
State Health Departments
Thanks to this search function on the CDC's website, you can locate your state health department, which can then help you find direct access to your county’s health department. Your local health department will likely provide updated information on flu activity in your area, as well as information on how to access vaccinations.
World Health Organization (WHO)
The WHO’s global influenza website provides worldwide surveillance information on flu outbreaks and what prevention efforts are taking place. It also provides information from its conferences regarding future strategies to combat the flu.
Best Flu Vaccination Information
CDC — Vaccine Safety
The CDC’s flu vaccine page provides up-to-date information on approved influenza vaccines, along with potential side effects.
National Vaccine Information Center
This independent nonprofit provides extensive information on vaccine science and includes research on the effectiveness of specific vaccines.
This U.S. Department of Health and Human Services site educates the public on various vaccine-preventable illnesses, including influenza. The flu section of the site includes basic information about the flu vaccine and a search tool to help you find places to get vaccinated in your area.
Best Information for Colds
This website offers information that will help you determine whether your symptoms are related to a cold and when you need to see a doctor, and offers preventive tips that may help you avoid getting sick.
National Library of Medicine
The common cold section of the MedlinePlus website provides comprehensive information on the causes and symptoms of the common cold, as well as links to information on how to determine whether you are suffering from a cold, the flu, or an allergy. It also includes information on potential treatments and therapies.
Best Resources for Parents
This American Academy of Pediatrics site focuses on how to identify flu symptoms in your children, the potential treatments, and preventive tips.
KidsHealth — Flu
This website’s flu section offers basic educational and preventive information on keeping your family healthy and how to treat a child’s flu symptoms.
KidsHealth — Colds
The KidsHealth site also has a page dedicated to providing general information on common cold treatments for kids and potential complications.
Best Apps for Combating the Flu
The CDC’s FluView app allows you to track flu activity by region, which can also be helpful if you plan on traveling.
Type in your location, your reason for seeing a doctor, and your insurance carrier and Zocdoc will help you book a doctor’s appointment in your area.
Find more apps to help you fight the flu in our article, 7 Apps to Help You Fight the Flu.
Editorial Sources and Fact-Checking
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- Flu Season. Centers for Disease Control and Prevention. September 28, 2021.
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- What You Should Know About Flu Antiviral Drugs. Centers for Disease Control and Prevention. August 31, 2021.
- Who Should and Who Should Not Get a Flu Vaccine. Centers for Disease Control and Prevention. August 24, 2021.
- Colds in Children. Pediatrics and Child Health. October 2005.
- Similarities and Differences Between Flu and COVID-19. Centers for Disease Control and Prevention. June 7, 2021.