Coronavirus ​Disease ​2019 ​(COVID-​19)​

What is COVID-19?

Coronavirus disease 2019 (COVID-19) is an infectious disease that most often causes a respiratory illness. It's caused by a virus called SARS-CoV-2. There are many types of coronavirus. They are a common cause of bronchitis. They may sometimes cause lung infection (pneumonia). Symptoms can range from mild to severe respiratory illness. These viruses are also found in some animals.

Like other viruses, the virus that causes COVID-19 changes (mutates) all the time. This leads to variants that can easily spread, including the Delta and Omicron variants. They may cause milder or more severe symptoms.

COVID-19 information is updated regularly. Visit the CDC website for the latest information. Or call 800-CDC-INFO (800-232-4636).

What causes COVID-19?

The virus SARS-CoV-2 causes COVID-19. The original source of the virus is unknown. The virus infects people and spreads fairly easily. Some people who have been infected may be unsure how or where they became infected. The virus is most commonly spread through droplets of fluid that a person expels into the air by talking, coughing, singing, or sneezing. It some cases, it may be spread if you touch a surface with virus on it, such as a handle or object, or the skin of an infected person, and then touch your eyes, nose, or mouth.

Who is at risk for COVID-19?

You are at risk for infection if you’ve been in close contact with people who are actively infected or sick with this virus. You are at higher risk if you are not fully vaccinated and:

  • Recently traveled to or live in an area with a COVID-19 outbreak

  • Had contact with a person who was diagnosed with or who may have COVID-19

What are the symptoms of COVID-19?

Symptoms can vary a lot from person to person. Some people have no symptoms (this is called asymptomatic). Some people have mild symptoms, and some people report feeling very sick. Symptoms may appear 2 to 14 days after contact with the virus. Symptoms can include:

  • Fever or chills

  • Coughing

  • Trouble breathing

  • Sore throat

  • Stuffy or runny nose

  • Headache or body aches

  • Tiredness (fatigue)

  • Nausea, vomiting, diarrhea, or belly (abdominal) pain

  • New loss of sense of smell or taste

  • Rash

You can check your symptoms with the CDC’s Coronavirus Self-Checker.

How is COVID-19 diagnosed?

Your healthcare provider will look at the risk for COVID-19 in your community and with your contacts and travel, and will ask about your symptoms. If your healthcare provider thinks you may have the COVID-19 virus, they will suggest testing for the virus. Know your testing options with the CDC's COVID-19 Viral Testing Tool . COVID-19 is diagnosed by:

  • Diagnostic test. Diagnostic tests tell if you have a current COVID-19 infection. There are 2 types of diagnostic tests:

    • Viral (molecular) test. You may also hear it called a PCR or RT-PCR test. Viral tests are very accurate. A viral test looks for the SARS-CoV-2 virus's genetic material. There are a few ways to do this. A nose-throat swab may be wiped inside your nose to the very back of your throat. Other tests are either done by nose or throat swab. Or a sample of your saliva may be taken. Availability of tests vary by location. Depending on the test, some results are back within about 30 minutes. Some tests must be sent to a lab and can take several days before the results are back. Home test kits are now available but vary by location. Some need a prescription. Some kits get results quickly at home. Others must be sent to a lab for the results.

    • Antigen test. This looks for proteins from the SARS-CoV-2 virus. This is done by a nose or throat swab, or sometimes by saliva. Depending on the test, some results are back in about 15 to 30 minutes. Positive results are highly accurate, but false positives can happen, especially in places where few people have the virus. Antigen tests are more likely to miss a COVID-19 infection than a viral (molecular) test. If your antigen test is negative but you have symptoms of COVID-19, your healthcare provider may order a viral test.

The FDA has authorized a COVID-19 breath test. It finds signs of a SARS-CoV-2 infection in the breath. The test is done at providers' offices, hospitals, and mobile testing sites. It's not widely available at this time.

If your healthcare provider thinks or confirms that you have COVID-19, you may have other tests. These tests may include:

  • Antibody blood test. Antibody tests can be done to find out if a person has recently been infected with the virus. The accuracy and availability of antibody tests vary. An antibody test may not be able to show if you have a current infection because it can take up to a few weeks after infection to make antibodies. Current antibody tests can't tell whether you are immune from COVID-19 and are not approved to test for immunity.

  • Sputum culture. A small sample of mucus coughed from your lungs (sputum) may be collected if you have a moist cough. It may be checked for the virus or to look for pneumonia.

  • Imaging tests. You may have a chest X-ray or CT scan.

Note about re-infection and immunity

You can be re-infected with COVID-19 especially after being exposed to a new variant or if you did not develop immunity after vaccination or from a prior COVID episode. It's not yet known how long immunity may last after being infected with the virus or getting a COVID-19 vaccine.

How is COVID-19 treated?

The most proven treatments right now are those to help your body while it fights the virus. This is known as supportive care. If you have confirmed COVID-19, talk with your healthcare provider about your situation and risk. You may qualify for certain medicines authorized by the FDA to prevent severe COVID-19 infection. Supportive care may include:

  • Getting rest. This helps your body fight the illness.

  • Staying hydrated. Drinking liquids is the best way to prevent dehydration. Try to drink 6 to 8 glasses of liquids every day, or as advised by your provider. Also check with your provider about which fluids are best for you. Don't drink fluids that contain caffeine or alcohol.

  • Taking over-the-counter (OTC) pain medicine. These are used to help ease pain and reduce fever. Follow your healthcare provider's instructions for which OTC medicine to use.

For severe illness, you may need to stay in the hospital. Care during severe illness may include:

  • IV (intravenous) fluids. These are given through a vein to help keep your body hydrated.

  • Oxygen. Supplemental oxygen or ventilation with a breathing machine (ventilator) may be given. This is done so you get enough oxygen in your body.

  • Prone positioning. Depending on how sick you are during your hospital stay, your healthcare team may turn you regularly on your stomach. This is called prone positioning. It's done to help increase the amount of oxygen you get to your lungs. Follow your healthcare team's instructions on position changes while you're in the hospital. Also follow their discharge advice on the best positions to help your breathing once you go home.

  • Antiviral medicines. Antiviral medicines stop the SARS-CoV-2 virus from spreading in the body. The FDA has authorized antiviral medicines to treat mild to moderate COVID-19 in certain people who are more likely to get very sick. These treatments are not available for everyone. Talk with your healthcare provider to learn more.

  • Steroids and other anti-inflammatory medicines. These are used to treat the intense inflammation that can occur with COVID-19. This inflammation is a major cause of progressive respiratory symptoms, kidney failure and death.

  • Monoclonal antibodies. These were once used for earlier COVID-19 strains, but monoclonal antibody treatment is not effective for the Omicron strains. Talk with your provider to learn more.

  • COVID-19 convalescent plasma. Plasma is the liquid part of blood. People who had COVID-19 may be asked to donate plasma. This is called COVID-19 convalescent plasma. The plasma may have antibodies. Some people with COVID-19 and a very weak immune system may benefit from this treatment. Your provider can help decide if this treatment is right for you.

What are possible complications of COVID-19?

The virus can cause infection in the lungs or kidneys. It can also cause heart disease, brain and spinal symptoms, and other complications. In some cases, this can cause death, especially in older adults and people who have serious health conditions such as heart or lung disease or diabetes. Many people have ongoing fatigue, shortness of breath, racing heart, loss of appetite or change of taste or smell after COVID-19, and these can persist for weeks or months.

Rarely, some children have developed severe complications called multisystem inflammatory syndrome in children (MIS-C). MIS-C seems to be similar to Kawasaki disease, a rare condition causing inflammation of blood vessels and body organs. MIS can also occur in adults, but less frequently The CDC advises healthcare providers to report to local health departments any person under age 21 years old who is ill enough to be in the hospital and has all of the following:

  • A fever over 100.4°F (38.0°C) for more than 24 hours and a positive SARS-CoV-2 test or exposure to the virus in the last 4 weeks

  • Inflammation in at least 2 organs such as the heart, lungs, or kidneys with lab tests that show inflammation

  • No other diagnoses besides COVID-19 explain the child's symptoms

What can I do to prevent COVID-19?

Woman washing hands at kitchen sink.
To help prevent spreading the infection, wash your hands often, or use an alcohol-based hand sanitizer.

The best prevention is to have no contact with the virus. Follow safety advice from the CDC and your local area, such as keeping physical distance, wearing masks as advised, using good hand hygiene, and getting a COVID-19 vaccine.


The FDA and CDC advise vaccines for everyone 6 months and older to help prevent COVID-19. The vaccines can also make the illness less severe. It can keep you from needing to go to the hospital. And it can prevent the spread of the virus to others. No vaccine is 100% effective at preventing an illness. But getting a vaccine is important. COVID-19 vaccines are available for people as young as 6 months old. Pregnant or breastfeeding people are advised to be vaccinated. Expert groups including the American College of Obstetricians and Gynecologists and the CDC advise pregnant or breastfeeding people to talk with their healthcare provider about the vaccine.

Updated (bivalent) mRNA vaccines from Moderna and Pfizer are recommended. Other options to mRNA COVID-19 vaccines are available for people who can't or won't get an mRNA vaccine. These are Novavax and J&J Janssen COVID-19 vaccines.

COVID-19 vaccines are given as a shot (injection) into the muscle. Ask your healthcare provider which vaccine is best for you and your family

When traveling, protect yourself by staying current with your COVID-19 vaccines Be aware of travel precautions, both within the U.S. and abroad. For the most current CDC travel advisories and how to protect yourself, visit the CDC travel website at .

Booster shots

People age 6 months or older can get a COVID-19 booster shot several months after completing their primary series. Boosters can help with protection against COVID-19 that may have decreased over time after getting the primary series.

Booster advice varies by vaccine, age, health status, and COVID-19 variants. People ages 65 and older and some people who have a moderate to very weak immune system are advised to get an updated (bivalent) mRNA booster. Talk with your provider about your risk and how this applies to you.

Protect yourself from COVID-19

  • Know your area's COVID-19 Community Level. This will help you know what to do if you've been exposed.

  • Wear a high-quality, well-fitted mask as advised based on your area's Community Level. If you are in an area with high Community Level, wear a well-fitted mask as advised. See the CDC's mask website at

  • If you have COVID-19 symptoms, get tested right away and stay home until you have your results. Wear a mask as soon as you find out you were exposed. See details on the CDC website at

  • Improve ventilation in your home and spend more time outdoors if possible. For more ventilation tips, see the CDC website at

  • If you are at risk for severe COVID-19, consider taking extra precautions such as wearing a mask in public or not attending non-essential indoor activities in public where you could be exposed.

  • Wash your hands often with soap and clean, running water for at least 20 seconds.

  • If you don’t have access to soap and water, use an alcohol-based hand sanitizer often. Make sure it has at least 60% alcohol.

  • Don't touch your eyes, nose, or mouth unless you have clean hands.

  • As much as possible, don't touch high-touch public surfaces such as doorknobs and handles, cabinet handles, and light switches. Don't shake hands.

  • Clean home and work surfaces often with disinfectant. This includes desk surfaces, printers, phones, kitchen counters, tables, fridge door handle, bathroom surfaces, and any soiled surface. Closely follow disinfectant label instructions. See the CDC’s cleaning website for detailed instructions.

  • Cough or sneeze into a tissue, then throw the tissue into the trash. If you don't have tissues, cough or sneeze into the bend of your elbow.

  • Stay informed about COVID-19 in your area. This is because instructions are changing regularly and vary by where you live. Follow local instructions about being in public. Be aware of events in your community that may be postponed or canceled, such as school and sporting events.

  • Stay away from people who are sick.

  • Check your home supplies. Consider keeping a 2-week supply of medicines, food, and other needed household items.

  • Make a plan for childcare, work, and ways to stay in touch with others. Know who will help you if you get sick.

  • Experts don't know if animals spread SARS-CoV-2. But it's always a good idea to wash your hands after touching any animals. Don't touch animals that may be sick.

  • Don’t share eating or drinking utensils with sick people.

  • Don’t kiss someone who is sick

If you have symptoms or have been diagnosed with COVID-19

The CDC updates isolation information regularly as COVID-19 transmission changes. See the CDC's website for current, detailed information about isolation. Also follow your local area's instructions on testing and staying home. Regardless of your vaccine status, these guidelines apply to you if you have symptoms of COVID-19 or a confirmed case. Confirmed means you have a positive COVID-19 test, even if you don’t have symptoms. If you have COVID-19:

  • Stay home at least 5 days and isolate in your home. Separate from others as much as possible. You are most likely infectious during these first 5 days. Day 0 is the first day you tested or first had symptoms. Day 1 is the first full day after your symptoms started or the first full day following your test.

  • Stay away from work, school, and public places. Limit physical contact with family members and pets. Stay is a separate room or area with its own bathroom if available. Don't kiss anyone or share eating or drinking utensils. Clean surfaces you touch with disinfectant. This is to help prevent the virus from spreading.

  • Monitor your symptoms. If you didn't have symptoms but develop some within 10 days of when you were tested, day 0 starts over from the day your symptoms started. If you have an emergency warning sign, like trouble breathing, seek emergency care now.

  • Don't travel.

  • Take steps to improve airflow in your home. This may include increasing the filtration in your heating and air conditioning unit, using high-efficiency (HEPA) cleaners, and turning your thermostat to the "on" position instead of "auto" to circulate air continuously.

  • Wear a high quality, well-fitting mask if you must be around others at home or in public. Don't go places where you are unable to wear a mask.

  • If you need to go to a hospital or clinic, expect that the healthcare staff will wear protective equipment such as masks, gowns, gloves, and eye protection. You may be told to enter or stay in a separate area. This is to prevent the possible virus from spreading.

  • Tell the healthcare staff about recent travel. This includes local travel on public transport. Staff may need to find other people you have been in contact with. This is called contact tracing.

  • Follow all instructions the healthcare staff give you.

  • End isolation based on how serious your COVID-19 symptoms were.

    • If you have COVID-19 but no symptoms, you may end isolation after day 5. Continue to wear a mask around others for 5 more days (through day 10).

    • If you have mild COVID-19 with symptoms, you may end isolation after day 5 if you have fever-free for 24 hours without using fever-reducing medicine such as acetaminophen and your symptoms are improving. If your symptoms have not improved, continue to isolate until they improve. Continue wearing a mask through day 10. Or, if you have 2 negative antigen tests at least 48 hours apart, you may remove your mask sooner than day 10.

    • For moderate or severe COVID-19, your isolation advice will be different. For moderate COVID-19, you may need to isolate through day 10. Moderate COVID-19 means you had difficulty breathing or shortness of breath. If you had severe COVID-19 (you were in the hospital) or you have a weak immune system and COVID-19, your provider will instruct you on when you can end isolation.

If you have been exposed to someone with COVID-19

There are steps you can take to protect others if you have been exposed to someone with COVID-19. Follow these steps regardless of your vaccination status.

  • If you've been exposed to someone with COVID-19, wear a mask around others, even if you've been vaccinated. Wear a mask as soon as you find out you were exposed. Day 0 the day of your last exposure to someone with COVID-19. Start counting from day 1. Keep wearing a mask through day 10. Do not go places where you are unable to wear a mask.

  • Take extra precautions if you will be around people with a weak immune system or who are more likely to get very sick from COVID-19. Consider delaying visits with them. If you need to be with them, maintain distance and wear a high-quality, well-fitted mask.

  • Watch for symptoms of COVID-19. If you develop symptoms, get tested and isolate immediately. If you have an emergency warning sign, like trouble breathing, seek emergency care now.

  • Get tested at day 6 (at least 5 full days after your last exposure). Test even if you don't have symptoms. If your test result is positive, isolate at home for 5 days. If you develop symptoms within 10 days of when you were tested, the clock restarts at day 0 on the day you started having symptoms.

If you've had COVID-19 in the last 90 days and have been re-exposed, contact your healthcare provider for advice. It's possible to get COVID-19 again. This is because of new variants of the virus.

How to manage COVID-19

If you've been diagnosed with COVID-19:

  • Stay home. Don’t leave your home unless you need to get medical care. Don't go to work, school, or public areas. Don't use public transportation or taxis.

  • Follow all instructions from your healthcare provider. Call your healthcare provider’s office before going. They can prepare and give you instructions. This will help prevent the virus from spreading.

  • Limit contact with other people in your home and don't have visitors in your house

  • Wear a well-fitting face mask. This is to protect other people from your germs. If you are not able to wear a mask, your caregivers should when you are in the same room with them. Wear the mask so that it covers your nose, mouth, and chin. Make sure there is no air is flowing from the top, bottom, or sides of your mask.

  • Don’t share household items or food.

  • Cover your face with a tissue when you cough or sneeze. Throw the tissue away. Then wash your hands.

  • Wash your hands often.

If you are caring for a sick person:

  • Follow all instructions from healthcare staff.

  • Wash your hands often.

  • Wear protective clothing as advised.

  • Make sure the sick person wears a mask. If they can't wear a mask, don't stay in the same room with the person. If you must be in the room, wear a face mask. Wear the mask so that it covers both the nose and mouth.

  • Keep track of the sick person’s symptoms.

  • Clean surfaces, fabrics, and laundry thoroughly.

  • Keep other people and pets away from the sick person.

When should I call my healthcare provider?

Call your healthcare provider:

  • If you’ve been exposed to COVID-19 and have symptoms

  • If you have been diagnosed with COVID-19 and your symptoms are worse

Key points about COVID-19

  • COVID-19 is mainly a respiratory illness but more severe cases can involve many parts of the body.

  • It's caused by a new (novel) type of coronavirus called SARS-CoV-2. The virus is mainly spread through droplets of fluid that a person coughs or sneezes into the air. It may be spread if you touch a surface with virus on it, such as a handle or object, or the skin of someone with the infection, and then touch your eyes, nose, or mouth.

  • The best way to protect yourself from COVID-19 is to get vaccinated and to follow safety precautions. Wash your hands often and disinfect high touch surfaces like door knobs. Monitor for symptoms of COVID-19. Follow safety precautions, including social distancing and mask requirements. See the CDC's safety precautions.

  • Know your community's COVID-19 Community Level and protection guidelines.

  • Several vaccines are available to prevent COVID-19 in people as young as 6 months of age. Pregnant or breastfeeding people are advised to be vaccinated. The vaccines are given as a shot (injection) in the muscle. Doses vary by age and health status.

  • People age 5 or older can get a COVID-19 booster shot. Talk with your healthcare provider about which vaccine is advised based on age and overall health.

  • Symptoms include fever, coughing, and trouble breathing. Some people report digestive upset, loss of appetite, runny nose, headache and body aches, chills or repeated shaking with chills, and new loss of taste and smell. In some cases, this virus can cause lung infection (pneumonia).

  • If you have COVID-19, treatment is given to help your body while it fights the virus. This is known as supportive care. In addition, those who are more likely to get very sick from COVID-19 will be offered certain medicines and other treatments aimed at the virus and the inflammation it causes. If you develop COVID-19 and are at risk of serious illness, contact your healthcare provider right away to discuss medicines and treatment options.

  • If you are or were in an area with COVID-19 and have a fever or other symptoms (even if you've been fully vaccinated), stay home away from other people. See the CDC website about how to protect yourself and others .

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you don't take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions.

Date last modified: 4/24/2023

Online Medical Reviewer: Barry Zingman MD
Online Medical Reviewer: L Renee Watson MSN RN
Date Last Reviewed: 9/1/2021
© 2000-2023 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.