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Coronavirus Disease 2019 (COVID-19)

What is COVID-19?

Coronavirus disease 2019 (COVID-19) is an infectious disease that is most often causes a respiratory illness. It's caused by a new (novel) coronavirus called SARS-CoV-2. There are many types of coronavirus. Coronaviruses are a very 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.

All U.S. states and every country around the world have reported cases of COVID-19. 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 variant. They may cause milder or more severe symptoms. COVID-19 is a rapidly-emerging infectious disease. This means that scientists are actively researching it.

There are information updates 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 spreads and infects people fairly easily. Some people who have been infected in an area 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 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 Follow all instructions from your healthcare provider. 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.

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. For serious COVID-19, you may need to stay in the hospital. 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.

  • Remdesivir. The FDA has approved an IV (intravenous) antiviral medicine called remdesivir. It works by stopping the spread of the SARS-CoV-2 virus in the body. It's approved for people in the hospital with Covid-19. It's for people 12 years and older who weigh more than 88 pounds (40 kgs). Remdesivir is approved only for people who need to be treated in the hospital. In certain cases, it may also be used for people younger than 12 years or who weigh less than 88 pounds (40 kgs).

  • 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.

  • COVID-19 convalescent plasma. People who have had COVID-19 and are fully recovered may be asked by their healthcare team to consider donating plasma. This is called COVID-19 convalescent plasma donation. Plasma from people fully recovered from COVID-19 may contain antibodies to help fight COVID-19 in people who are currently ill with the disease. The FDA has authorized it for emergency use in certain people with early but serious COVID-19. Talk with your provider to learn more about convalescent plasma donation and whether you qualify to donate.

  • Monoclonal antibody therapy. The FDA has authorized these treatments for emergency use for certain people who have a positive COVID-19 viral test and have mild to moderate symptoms but are not in the hospital. Monoclonal antibody therapy reduces the risk of needing emergency room or hospital care for COVID-19, and may reduce the chance of needing a ventilator or dying from the illness. It's approved for people 12 years and older who weigh at least 88 pounds (40 kg) and are at increased risk for progressive or severe COVID-19. This includes people who are 65 years or older and people with certain chronic conditions. Monoclonal antibody therapy is not approved for people who:

    • Are hospitalized for COVID-19, or

    • Need oxygen therapy for COVID-19, or

    • Need oxygen therapy for a chronic condition and need to have oxygen flow increased because of COVID-19.

What are possible complications of COVID-19?

The virus can cause infection (pneumonia) in lungs, kidney or 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?

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 such as social distancing, wearing masks, using good hand hygiene, and getting a COVID-19 vaccine.

Vaccines

The FDA has approved several vaccines to prevent COVID-19 and reduce the severity of illness if you get the virus. No vaccine is ever 100% effective in preventing any illness, but the COVID-19 vaccines work well and are safe. One vaccine has been approved for people as young as 5. Talk with your healthcare provider about your risks and which vaccine may be best for you and your family.

Pregnant or breastfeeding people are advised to be vaccinated. Expert groups including ACOG and the CDC advise pregnant or breastfeeding people to talk with their healthcare provider about the vaccine.

The vaccines are given as a shot (injection) in the arm muscle. A 1-dose (Johnson & Johnson) or 2-dose (either Pfizer or Moderna) vaccine may be given. If you get the 2-dose vaccine, the second dose is given several weeks after the first.

CDC recommends not traveling until you are fully vaccinated against COVID-19. This is because travel raises your chance of getting and spreading the infection. Fully vaccinated means 2 weeks after getting either the 1-dose or the second shot of the 2-dose vaccine. Be aware of travel precautions, both within the U.S. and abroad. For the most current CDC travel advisories, visit the CDC website.

Who needs a third dose?

People with a very weak immune system may not build up enough antibodies to fight COVID-19 after getting the first 2 doses of either 2-dose vaccines. This includes people who have had a solid organ transplant or who have a condition such as cancer or HIV that causes a very weak immune system. For these people, a third dose of Pfizer or Moderna is advised. This is considered part of their vaccine series (primary series), not a booster. The third shot is given at least 28 days after the second dose. Talk with your healthcare provider about your own case and risk.

Booster doses

Everyone age 18 or older can get a COVID-19 booster shot. Here are your options.

Pfizer or Moderna booster

A booster shot of the Pfizer or Moderna vaccines is advised for many people. The booster shot is to be given at least 6 months after your primary series. Talk with your healthcare provider about your situation and risk. The CDC says these people should get a Pfizer or Moderna booster shot:

  • People ages 50 and older.

  • People ages 18 and older living in long-term care facilities.

The CDC states people 18 to 49 may choose to get the booster depending on their specific case and risk. This includes people with certain health conditions or whose job or living setting puts them at higher risk for COVID-19.

Johnson & Johnson booster

A booster shot of the Johnson & Johnson COVID-19 vaccine is also advised for people ages 18 and older who got their first dose 2 or more months ago.

Mix and match

You may be able to choose which vaccine you get for your booster shot. This is called mix and match. Talk with your healthcare provider about how this applies to you.

Prepare and protect yourself from COVID-19

  • Wear a mask as advised. The CDC advises wearing a medical mask or cloth face mask with several layers of washable, breathable fabric and a nose wire. Or you can wear a disposable medical mask with a cloth mask over it. Wear the mask so that it covers both your nose and mouth.

    • The CDC advises all people older than 2 who are not fully vaccinated to wear a mask and stay 6 feet away from others while in public.

    • The CDC advises people with weak immune systems, even if fully vaccinated, to continue wearing masks and to stay 6 feet away from others while in public.

    • If you are fully vaccinated, you can take part in many activities that you did before COVID-19. But be aware of safety precautions in your area. To protect against the variants, the CDC advises all people over age 2, including those who are fully vaccinated, to wear a mask indoors in public if you are in an area of high numbers of COVIDS-19 cases. See the CDC's county data website for current transmission information in your area.

  • 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 are sick with COVID-19 symptoms

  • Stay home. Call your healthcare provider and tell them you have symptoms of Covid-19. Do this before going to any hospital or clinic. Follow your provider's instructions about testing and staying home. You may be advised to isolate yourself at home. This is called self-isolation or self-quarantine.

  • Don’t panic. Keep in mind that other illnesses can cause similar symptoms.

  • Stay away from work, school, and public places. Limit physical contact with family members and pets. 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.

  • 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.

  • Wear a 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 both the nose and mouth.

  • 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.

If you have been exposed to someone with COVID-19

  • If you are fully vaccinated, the risk of contracting COVID-19 is much lower after exposure if you've been fully vaccinated. But if you have had close contact with someone with COVID-19, you should get tested 5 to 7 days after being exposed, even if you don't have symptoms. If your test is negative, you don't need to isolate, but wear a mask indoors in public for 14 days after exposure. If your test is positive, isolate at home for 10 days and monitor your health. At day 11, if you don't have symptoms, you can stop isolating, but wear a mask indoors in public until your test is negative. If you develop symptoms, stay home. Stay informed of your community's instructions as this advice may change as new variants of the virus appear.

  • If you have never had COVID-19 and have not been fully vaccinated but are exposed , stay home and monitor your health for at least 14 days. This is called quarantine. Limit contact with others. Don't go to work, school, or out in public. Keep watch for symptoms of the virus. Tell your provider right away if you have symptoms. Take your temperature every morning and evening for at least 14 days. This is to check for fever. Keep a record of the readings. Watch for other symptoms such as cough and shortness of breath.

  • If you have not been fully vaccinated but are exposed to COVID-19, you will be advised to quarantine to help prevent spread of COVID-19. Follow your provider's instructions about quarantine and testing. If you have not been fully vaccinated and have COVID-19 symptoms, the CDC recommends viral testing

  • If you've had COVID-19 in the last 3 months but are fully recovered without symptoms and you have been exposed to someone with COVID-19, you are less likely to develop COVID-19 again, but it is possible. This is due to new variants of the virus and because some people cannot mount a strong immune response after the illness. Limit your contact with others, call your provider, strongly consider getting tested for the virus, and monitor for symptoms.

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 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 both the nose and mouth.

  • 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 recently traveled or have been in an area with 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 CDC's safety precautions.

  • Several vaccines are available to prevent COVID-19. One vaccine has been approved for people as young as 5. Pregnant or breastfeeding people are advised to be vaccinated. The vaccines are given as a shot (injection) in the arm muscle. A 1-dose or 2-dose vaccine may be given. If you get the 2-dose vaccine, the second dose is given several weeks after the first.

  • Some people with certain conditions may need a third dose of Pfizer or Moderna as part of the primary series.

  • Everyone age 18 or older can get a COVID-19 booster shot. Booster doses are available for Pfizer, Moderna, and Johnson & Johnson vaccines. You may choose which vaccine you get as a booster. This is called mix and match. Talk with your healthcare provider about booster doses.

  • 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 with more serious cases or those at risk for serious disease will be offered certain medicines and other treatments aimed at the virus and/or the inflammation it causes.

  • 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 away from other people. Call your healthcare provider. Explain that you have been exposed to COVID-19 and have symptoms. Do this before going to any hospital or clinic so as not to spread an illness to others. Wait for instructions.

  • If your healthcare provider thinks you may have COVID-19, they will work closely with your local health department. Follow all instructions from your healthcare provider.

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: 11/22/2021

Online Medical Reviewer: Barry Zingman MD
Online Medical Reviewer: L Renee Watson MSN RN
Date Last Reviewed: 9/1/2021
© 2000-2021 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.