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.
Both the common cold and the flu are contagious, but cold symptoms tend to be milder and improve within a week to 10 days, according to the Mayo Clinic. (1) While most people who get the flu recover in less than two weeks, the symptoms are more severe, and serious complications, such as?pneumonia,?bronchitis, and?sinus?or?ear?infections, can develop, notes the Centers for Disease Control and Prevention (CDC). (2)
Since colds and the flu are caused by viruses, rather than bacteria,?antibiotics?are not an effective treatment option.
Common Questions & Answers
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, an infectious diseases and infection control consultant at South Nassau Communities Hospital in Oceanside, New York.
Symptoms that the common cold and flu share may include:
The flu is usually accompanied by higher fever (102 degrees F or higher), and influenza symptoms?tend to come on more suddenly.
"Run-of-the-mill colds usually make you feel lousy but should not interfere with daily activities," says?Stephen Russell, MD, an assistant professor of medicine at the University of Alabama in Birmingham and the lead physician of the UAB Moody Health Clinic.
While most colds don’t require a visit to the doctor, they can turn into something more serious. According to the American Academy of Family Physicians, some warning signs to look for include high fever,?shortness of breath, and symptoms that last more than 10 days or continue to worsen. (3)
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, the elderly, and people with a compromised immune system.
Factors that can increase your risk of becoming infected include:
Children younger than 6 are more at risk for colds and flu, especially if they’re in a daycare or school. Adults over age 65 are more susceptible to the flu and related complications.
Seasonal flu activity typically occurs between October and May (flu season), although flu viruses are around all year.
Similarly, most people develop colds in the winter and spring, but they can occur anytime. According to the CDC, adults average two to three colds each year. (4)
Weakened Immune System
Viruses can more easily infiltrate the body if you have a weakened immune system. Certain chronic illnesses, such as?cancer,?HIV or AIDS, and?autoimmune diseases raise the risk of catching a cold or the flu.
Chronic smoking makes your respiratory system more vulnerable to cold and flu viruses and complications.
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.
What Types of Flu Are There?
Like a common cold, the flu is caused by viruses. There are four types of influenza viruses: A and B, which are most commonly associated with seasonal flu activity and epidemics; C, which is relatively rare and causes mild respiratory illness; and D, which primarily affects cattle.
There are many subtypes of influenza A viruses, based on two proteins — hemagglutinin (H) and neuraminidase (N) — found on the surface of the viruses. Two strains of influenza A found in human beings are the H1N1 strain and the H3N2 strain.
A novel strain of influenza A (H1N1) virus, known as swine flu because it’s typically spread among pigs, led to a flu pandemic in 2009. Between April 2009 and April 2010, the CDC estimates that there were 60.8 million swine flu cases in the United States, which led to more than 274,000 hospitalizations and nearly 12,500 deaths. (5) The influenza pandemic of 1918 was an H1N1 virus of avian origin.
The H3N2 virus usually causes more severe symptoms and can be particularly dangerous to the young and elderly. Flu seasons that have many cases of the H3N2, such as the 2017–2018 flu season, tend to have higher rates of hospitalizations and flu-related deaths. H3N2 is particularly resistant to the flu vaccine, and it mutates more rapidly than other strains.
Less common than influenza A, these viruses cause similar symptoms and can lead to outbreaks or pandemics. Influenza B is not categorized by subtypes, but there are two strains of the virus: Yamagata and Victoria.
A study published in?Clinical Infectious Diseases?in July 2014 challenged the perception that influenza B was milder than influenza A. (6)
Like influenza A and B, these viruses are found in humans. But influenza C viruses are milder and do not cause epidemics. Seasonal flu vaccines, which contain strains of influenza A and B, do not protect against influenza C viruses.
This strain of influenza is not known to cause illness in humans. It primarily affects cattle, though researchers at South Dakota University note that it could eventually form a new strain that poses more of a threat to humans. (7)
How Are Cold and Flu Diagnosed?
To diagnose the flu, doctors sometimes use a rapid influenza diagnostics test, notes the CDC. (8) Swab samples from the nose or back of the throat are tested for influenza viral antigens. Test results are usually ready in less than 30 minutes, but they are not always accurate. There are other, more reliable flu tests that can be performed only in hospitals or specialized laboratories.
Duration of Cold and Flu
The duration of a cold or flu varies depending on the virus involved and the 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.
Cold symptoms typically subside within 7 to 10 days, while the flu may last up to two weeks. Even after most symptoms subside, some, like fatigue and cough, can linger for several days or weeks more.
“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.
Treatment and Medication Options for Cold and Flu
There is no cure for either the flu or the common cold. There are over-the-counter options that can ease throat pain and cough, decongest the nose and?sinuses, and lessen body aches and headaches.
Cold medicines and pain relievers can have side effects and pose health risks, especially for people who have preexisting conditions such as?high blood pressure. The Mayo Clinic cautions that children and teenagers with flu-like symptoms should never take?aspirin?for pain or fever, because it has been linked to the potentially life-threatening condition Reye's syndrome. (9)
Prescription antiviral drugs can be used to treat the flu. According to the CDC, when taken within two days of the appearance of flu symptoms, these drugs can shorten the time you are sick. (10) They can help high-risk patients avoid more serious flu-related complications.
There are four U.S. Food and Drug Administration (FDA)–approved antiviral drugs recommended by the CDC:?oseltamivir (Tamiflu),?peramivir,?zanamivir (Relenza Diskhaler), and?baloxavir marboxil (Xofluza).
Prevention of Cold and Flu
To avoid getting the flu in the first place, the CDC recommends that everyone 6 months and older get a flu vaccine every year. These vaccines protect against the viruses that public health officials anticipate will be most common during the upcoming flu season.
“The best tool to prevent the flu is getting the vaccine. It’s not perfect, but it’s the most effective thing we have,” says?Carol Baker, MD, a pediatric infectious disease specialist in Houston.
Common cold symptoms?typically develop about one to three days after exposure to cold-causing viruses.
These viruses can be spread through the air, personal contact, and respiratory secretions — things such as a handshake, touching contaminated objects, and exposure to an infected person’s sneezes or coughs.
"Most colds stem from viruses that are spread from person to person through close contact," says?William Schaffner, MD, a professor of preventive medicine at Vanderbilt University School of Medicine in Nashville, Tennessee.
There is no vaccine to prevent the common cold, but practicing good?hygiene?can reduce the risk of illness or spreading viruses to others. The CDC recommends washing your hands often for at least 20 seconds at a time and not touching your eyes, nose, or mouth with unwashed hands. (11)
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.
Research and Statistics: Who Gets Cold and Flu?
Most people feel the effects of the common cold or flu every year. Between 5 and 20 percent of the U.S. population gets the flu annually. (12) Adults average two or three colds each year; and young children may get sick as many as 8 to 10 times a year before they turn 2. (13)
There is a wealth of data available to track seasonal flu activity, including the CDC and World Health Organization websites, as well as local public health offices. There are also resources providing general information about colds and influenza viruses — from risk factors, prevention, and diagnosis to treatment.
COVID-19 and Cold and Flu
COVID-19, the disease caused by the novel coronavirus, and the flu are both contagious respiratory illnesses and share many symptoms, including fever or feeling feverish, chills, cough, difficulty breathing, fatigue, sore throat, runny or stuffy nose, body aches, and headache. You might even wonder, based on your symptoms, whether a severe cold is COVID-19.
One difference in possible symptoms: People with COVID-19 may experience a change or loss of taste or smell, which isn't a symptom of the flu.
COVID-19 and the flu are caused by different viruses. One doesn't cause the other, though you can contract both at the same time. Diagnostic testing can confirm which virus you're dealing with, notes the CDC. (14)
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
ACOG’s website Immunization for Women prioritizes providing patients and healthcare providers with a trusted source for the most up-to-date recommendations and guidelines on treating seasonal influenza and other vaccine-preventable diseases. It also provides a searchable ob-gyn directory.
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.
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 the elderly.
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.
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
The CDC’s flu vaccine page provides up-to-date information on approved influenza vaccines, along with potential side effects.
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
The 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.
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.
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.
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
- Common Cold. Symptoms and Causes.?Mayo Clinic. April 20, 2019.
- Flu Symptoms and Complications.?Centers for Disease Control and Prevention (CDC). August 31, 2020.
- Fashner J, Ericson K, Werner S. Treatment of the Common Cold in Children and Adults.?American Family Physician. July 15, 2012.
- Common Cold.?Centers for Disease Control and Prevention. March 18, 2019.
- Past Pandemics.?Centers for Disease Control and Prevention. August 10, 2018.
- Su S, Chaves S, Perez A, et al. Comparing Clinical Characteristics Between Hospitalized Adults With Laboratory-Confirmed Influenza A and B Virus Infection.?Clinical Infectious Diseases. April 18, 2014.
- New Virus Gets Official Name, Influenza D.?South Dakota State University. September 1, 2016.
- Rapid Influenza Diagnostic Tests.?Centers for Disease Control and Prevention. October 25, 2016.
- Common Cold: Diagnosis and Treatment.?Mayo Clinic. April 20, 2019.
- What You Should Know About Flu Antiviral Drugs.?Centers for Disease Control and Prevention. September 3, 2020.
- Common Colds: Protect Yourself and Others.?Centers for Disease Control and Prevention. February 11, 2019.
- Molinari NA, Ortega-Sanchez IR, Messonneir ML, et al. The Annual Impact of Seasonal Influenza in the U.S.: Measuring Disease Burden and Costs.?Vaccine. June 28, 2007.
- Colds in Children.?Pediatrics and Child Health. October 2005.
- Frequently Asked Influenza (Flu) Questions: 2020-2021 Season. Centers for Disease Control and Prevention. September 21, 2020.
- Influenza.?Centers for Disease Control and Prevention. September 28, 2020.
- Influenza.?Cleveland Clinic. November 29, 2019.
- Common Cold.?Mayo Clinic. April 20, 2019.
- Influenza.?Mayo Clinic. October 4, 2019.
- Influenza.?National Institute of Allergy and Infectious Diseases. June 12, 2020.
- Flu (Influenza). Vaccines.gov. Junes 2020.