What is the definition of COVID-19?

Coronavirus disease 2019 (COVID-19) is mainly a respiratory illness that causes fever, coughing, and shortness of breath, but many other symptoms can occur. COVID-19 is caused by a highly infectious virus, and it has spread throughout the world. Most people get mild to moderate illness. Older adults and people with certain health conditions are at high risk for severe illness and death.

What are the alternative names for COVID-19?

Coronavirus - 2019; Coronavirus - novel 2019; 2019 Novel coronavirus; SARS-CoV-2

What are the causes for COVID-19?

COVID-19 is caused by the SARS-CoV-2 virus (severe acute respiratory syndrome coronavirus 2). Coronaviruses are a family of viruses that can affect people and animals. They can cause mild to moderate respiratory illnesses, such as the common cold. Some coronaviruses can cause severe illness that can lead to pneumonia and even death.


COVID-19 most readily spreads to people within close contact (about 6 feet or 2 meters). When someone with the illness coughs, sneezes, sings, talks, or breathes, droplets and very small particles spray into the air. You can catch the illness if you breathe in these droplets and particles or they get in your eyes.

In some instances, COVID-19 may spread through the air and infect people who are more than 6 feet away. Small droplets and particles can remain in the air for minutes to hours. This is called airborne transmission, and it occurs especially in enclosed spaces with poor ventilation. However, it is more common for COVID-19 to spread through close contact.

Less often, the illness can spread if you touch a surface with the virus on it, and then touch your eyes, nose, mouth, or face. But this is thought to be a very uncommon way in which the virus spreads.

COVID-19 can spread from person to person quickly. As the virus spreads, it can change, and new variants will occur. This is expected. The Delta variant is now the most common in the United States. It spreads more easily and more quickly than early forms of the virus.  

The United States Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) consider COVID-19 a serious public health threat globally and in the United States. The situation continues to evolve, so it's important to follow current local guidance on how to protect yourself and others from getting and spreading COVID-19.

What are the symptoms for COVID-19?

COVID-19 symptoms range from mild to severe. Older people and people with certain existing health conditions have a higher risk of developing severe illness and death. Health conditions that increase this risk include:

  • Cancer
  • COPD (chronic obstructive pulmonary disease)
  • Dementia 
  • Down syndrome
  • Heart disease and stroke
  • HIV
  • Kidney, lung, or liver disease
  • Mental health conditions
  • Obesity (BMI of 25 or above)
  • Pregnancy
  • Organ transplantation
  • Sickle cell disease
  • Smoking (current or former)
  • Substance use disorders
  • Tuberculosis
  • Diabetes (type 1 and type 2)
  • Weak immune system (immunocompromised)

Symptoms of COVID-19 may include:

  • Fever
  • Chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue
  • Muscle aches
  • Headache
  • Loss of sense of taste or smell
  • Sore throat
  • Stuffy or runny nose
  • Nausea or vomiting
  • Diarrhea

(Note: This is not a complete list of possible symptoms. More may be added as health experts learn more about the disease.)

Some people may have no symptoms at all or may have some, but not all of the symptoms.

Symptoms may appear within 2 to 14 days after being exposed. Most often, symptoms appear around 5 days after exposure. However, you can spread the virus even when you do not have symptoms.

More severe symptoms that require seeking medical help right away include:

  • Trouble breathing
  • Chest pain or pressure that persists
  • Confusion
  • Inability to wake up
  • Blue lips or face

What are the current treatments for COVID-19?

If you are recovering at home, supportive care is given to help relieve symptoms. People with severe illness will be treated in the hospital. Some people are being given experimental medicines.

If you are being cared for in the hospital and are receiving oxygen therapy, treatment for COVID-19 may include the following medicines:

  • Remdesivir, an antiviral medicine, to help slow the virus. This medicine is given through the vein (IV).
  • Dexamethasone, a steroid medicine, to help reduce an overactive immune response in the body. If dexamethasone is not available, you may be given another corticosteroid such as prednisone, methylprednisolone, or hydrocortisone.
  • You may be given one or the other medicine, or both medicines together.
  • Depending on your condition, you may also receive baricitinib or tocilizumab to help reduce immune system activity.
  • You will be treated for any complications from the disease. For example, you may be given blood thinners to help reduce the chance of blood clots, or you may have dialysis if your kidneys do not function properly.

If you test positive for COVID-19 and are at high risk for serious illness from the disease, your provider may recommend medicines called monoclonal antibodies.

If given soon after you become infected, these medicines may help your immune system fight off the virus. They may be given to people with mild to moderate illness who are not hospitalized. 

Other possible treatments are being studied, such as plasma from people who had COVID-19 and have recovered, but there is not enough evidence to recommend them at this time.

Based on available evidence, current treatment guidelines from the National Institutes of Health recommend against using some drugs for COVID-19, including chloroquine, hydroxychloroquine, and ivermectin. Do not take any drugs to treat COVID-19 except those prescribed by your provider. Check with your provider before treating yourself or a loved one with vitamins, nutrients, or any medicines prescribed in the past for other health problems.

Treatments for COVID-19 continue to be evaluated and guidelines continue to evolve. For the latest information about treatment for COVID-19, please see Coronavirus disease 2019 (COVID-19) treatment guidelines from the Centers for Disease Control and Prevention.

What are the possible complications for COVID-19?

Complications can include:

  • Lasting COVID symptoms that continue weeks or months after infection with the virus (called long COVID)
  • Damage to the heart and blood vessels, kidneys, brain, skin, eyes, and gastrointestinal organs
  • Respiratory failure
  • Death

When should I contact a medical professional for COVID-19?

You should contact your provider:

  • If you have symptoms and think you may have been exposed to COVID-19
  • If you have COVID-19 and your symptoms are getting worse

Call 911 or the local emergency number if you have:

  • Trouble breathing
  • Chest pain or pressure
  • Confusion or inability to wake up
  • Blue lips or face
  • Any other symptoms that are severe or concern you

Before you go to a doctor's office or hospital emergency department (ED), call ahead and tell them that you have or think you may have COVID-19. Tell them about any underlying conditions you might have, such as heart disease, diabetes, or lung disease. Wear a cloth face mask with at least 2 layers when you visit the office or ED, unless it makes it too hard to breathe. This will help protect other people you come in contact with.

How do I prevent COVID-19?

COVID-19 vaccines are used to boost the body's immune system and protect against COVID-19. These vaccines are the best tool to help stop the COVID-19 pandemic. Adults and children age 5 years and older can get the COVID-19 vaccine to protect themselves from the virus.

To find out where to get a vaccine in your area, check with your local public health department. You can also use the CDC VaccineFinder.

Fully-vaccinated people can resume activities without wearing a mask or physically distancing, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance.

The CDC has recommendations for what it is safe to do once you are fully vaccinated. To reduce the risk of being infected with the Delta variant and possibly spreading it to others, wear a mask indoors in public if you are in an area of high transmission.

You might choose to wear a mask regardless of the level of transmission if:

  • You have a weakened immune system
  • You are at increased risk for severe disease because of your age or an underlying medical condition
  • A member of your household has a weakened immune system, is at increased risk for severe disease, or is unvaccinated 

 If you have COVID-19 or have symptoms of it, you must isolate yourself at home and avoid contact with other people, both inside and outside your home, to avoid spreading the illness. This is called home isolation or self-quarantine. You should do this immediately and not wait for any COVID-19 testing.

  • As much as possible, stay in a specific room and away from others in your home. Use a separate bathroom if you can. Do not leave your home except to get medical care.
  • Do not travel while sick. Do not use public transportation or taxis.
  • Keep track of your symptoms. You may receive instructions on how to check and report your symptoms.
  • Stay in touch with your doctor. Before you go to a doctor's office or emergency department (ED), call ahead and tell them that you have or think you may have COVID-19.
  • Use a face mask with at least 2 layers when you see your provider and anytime other people are in the same room with you. If you can't wear a mask, for example, due to breathing problems, people in your home should wear a mask if they need to be in the same room with you.
  • Avoid contact with pets or other animals. (SARS-CoV-2 can spread from people to animals, but it is not known how often this happens.)
  • Cover your mouth and nose with a tissue or your sleeve (not your hands) when coughing or sneezing. Droplets that are released when a person sneezes or coughs are infectious. Throw away the tissue after use.
  • Wash your hands many times a day with soap and running water for at least 20 seconds. Do this before eating or preparing food, after using the toilet, and after coughing, sneezing, or blowing your nose. Use an alcohol-based hand sanitizer (at least 60% alcohol) if soap and water are not available.
  • Avoid touching your face, eyes, nose, and mouth with unwashed hands.
  • Do not share personal items such as cups, eating utensils, towels, or bedding. Wash anything you have used in soap and water.
  • Clean all "high-touch" areas in the home, such as doorknobs, bathroom and kitchen fixtures, toilets, phones, tablets, and counters and other surfaces. Use a household cleaning spray and follow instructions for use.

You should remain at home, avoid contact with people, and follow the guidance of your provider and local health department about when to stop home isolation.

It's also important to help prevent the spread of the disease to protect people at high risk of serious illness and to protect providers who are at the front lines of dealing with COVID-19.

To find out what it happening in your community, check your local or state government website.

Learn more about COVID-19 and you:

  • Combatcovid.hhs.gov
  • www.cdc.gov/coronavirus/2019-ncov/index.html

For the latest research information:

  • Covid19.nih.gov

Information about COVID-19 from the World Health Organization:

  • www.who.int/emergencies/diseases/novel-coronavirus-2019
Respiratory system
Upper respiratory tract
Lower respiratory tract
Face masks prevent the spread of COVID-19
How to wear a face mask to prevent the spread of COVID-19
COVID-19 vaccine


Centers for Disease Control and Prevention website. COVID-19 vaccines for children and teens. www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/children-teens.html. Updated November 4, 2021. Accessed November 17, 2021.

Centers for Disease Control and Prevention website. COVID-19: How to protect yourself & others. www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html. Updated August 13, 2021. Accessed October 25, 2021.

Centers for Disease Control and Prevention website. COVID-19: Frequently asked questions about COVID-19 vaccination. www.cdc.gov/coronavirus/2019-ncov/vaccines/faq.html. Updated October 21, 2021. Accessed October 25, 2021.

Centers for Disease Control and Prevention website. COVID-19: Post-COVID conditions. www.cdc.gov/coronavirus/2019-ncov/long-term-effects.html. Updated September 16, 2021. Accessed October 25, 2021.

Centers for Disease Control and Prevention website. COVID-19: Public health guidance for community-related exposure. www.cdc.gov/coronavirus/2019-ncov/php/public-health-recommendations.html. Updated March 1, 2021. Accessed October 25, 2021.

Centers for Disease Control and Prevention website. COVID-19: Treatments your healthcare provider might recommend if you are sick. www.cdc.gov/coronavirus/2019-ncov/your-health/treatments-for-severe-illness.html. Updated March 23, 2021. Accessed October 25, 2021.

Centers for Disease Control and Prevention website. COVID-19: What to do if you are sick. www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/steps-when-sick.html. Updated March 17, 2021. Accessed October 25, 2021.

Centers for Disease Control and Prevention website. Delta variant: what we know about the science. www.cdc.gov/coronavirus/2019-ncov/variants/delta-variant.html. Updated August 26, 2021. Accessed October 26, 2021.

National Institutes of Health. COVID-19 treatment guidelines. What's new in the guidelines. www.covid19treatmentguidelines.nih.gov/about-the-guidelines/whats-new/. Updated October 19, 2021. Accessed October 25, 2021.

Clinical Trial
  • Status: Not yet recruiting
  • Phase: Phase 2
  • Intervention Type: Dietary Supplement
  • Participants: 60
  • Start Date: May 10, 2021
Assessment of the Clinical Effectiveness of Standardized Olive Leaf Capsules; as a Co-therapy in the Treatment of Non-hospitalized COVID-19 Patients; a Randomized Clinical Trial
Clinical Trial
  • Status: Not yet recruiting
  • Phase: N/A
  • Intervention Type: Device
  • Participants: 370
  • Start Date: May 27, 2021
Seawater Nasal Wash to Relieve COVID-19 Nasal Symptoms and Reduce SARS-CoV-2 Viral Load.