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(Coronavirus Disease 2019; COVID)


The Manual's Editorial Staff

Last full review/revision Mar 2022| Content last modified Mar 2022
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What is COVID-19?

What is a pandemic?

COVID-19 is a pandemic. That's an infection that's spreading rapidly in many parts of the world all at once.

What causes COVID-19?

COVID-19 is caused by a type of coronavirus called SARS-CoV-2. The virus spreads:

  • Mostly through the air, in droplets that an infected person spreads through a cough, sneeze, singing, or talking

  • Through touching things that infected people have touched and then touching your face

You can spread the virus that causes COVID-19 before you have any symptoms.

What is a coronavirus?

There are hundreds of different coronaviruses that are all related. Most of them infect only animals.

  • Only a few coronaviruses can infect people

  • Some of them cause only colds

  • Three coronaviruses cause very serious illness and can be fatal

What are the symptoms of COVID-19?

Many people with COVID-19 have almost no symptoms.

If you do get symptoms, you'll likely have:

  • Fever

  • Dry cough

  • Trouble breathing

  • Feeling really weak and tired

You may also have:

  • Runny nose

  • Sore throat

  • Loss of your sense of smell and taste

  • Headaches

  • Stomach problems such as nausea, vomiting, and diarrhea

A bad infection goes into your lungs, causing viral pneumonia. That will make you very short of breath. A bad infection can also affect a lot of organs, including your brain, heart, and kidneys.

Is COVID-19 fatal?

You can die from COVID-19. The older you are, the higher your risk of death. Most deaths occur in people over 50 years old. People over 80 are at very high risk. But even children and young adults can die.

How can I tell if I have COVID-19?

You should be tested for COVID-19 if you:

The most common test that a doctor or other healthcare worker does, called a PCR test (polymerase chain reaction test), uses:

  • A swab taken from your nose or throat

The swab is sent to a lab to look for the virus or other evidence of an infection. It can take a few days to get your results.

Antigen tests are a different type of test than a PCR test. Antigen tests can be done at home or in a healthcare setting and use a swab taken from your nose. They are generally less accurate than PCR tests. But antigen tests can provide rapid results (within 15 minutes).

A blood test can look for antibodies What are the main parts of the immune system? The immune system is your body's defense system. It helps protect you from illness and infection. The immune system's job is to attack things that don’t belong in your body, including: Germs... read more your body has made to defend against the virus. It takes your body a few weeks to make these antibodies, so this test is not useful when you first get sick. But it can help tell whether you were ever infected.

How is COVID-19 treated?

If you have a mild or moderate case, you'll:

  • Stay home and not go out or go near other people (isolation)

  • Wear a mask so you don't spread the virus

  • Take acetaminophen or ibuprofen for fever and aches

If you have a severe case, with breathing problems, you'll need to go to the hospital. Doctors will:

  • Give you oxygen

  • Sometimes, give you drugs

  • Sometimes, put you on a ventilator (machine to help you breathe)

You may need to be on a ventilator for up to a few weeks.

How can I prevent COVID-19?

  • The vaccines are safe and effective

  • You can't get COVID-19 from a COVID-19 vaccine

  • Vaccine effectiveness can decrease over time—a booster dose helps to “boost” how well your vaccine works

  • COVID-19 vaccines can cause mild side effects (a sore arm, body aches, headache, fever) for a day or two

  • You should get a COVID-19 vaccine even if you had a COVID-19 infection

There is a small chance of having a severe allergic reaction to any vaccine. This usually happens within a few minutes to 1 hour after getting a dose of the vaccine. An allergic reaction requires emergency treatment (call for emergency medical care [911 in the United States] or go to the nearest hospital).

In addition to being vaccinated, you should avoid being exposed to the virus. That can be difficult. People who can spread the virus may not have any symptoms, so you can't tell who has it and who doesn't. The CDC recommends additional ways to help avoid the virus based on COVID-19 Community Levels. Levels can be low, medium, or high. The level is determined by looking at the number of hospital beds being used, hospital admissions, and new COVID-19 cases in an area.

You should wear a well-fitting face mask, covering both mouth and nose:

  • When in indoor public places in areas where the COVID-19 Community Level is high, regardless of vaccination status

  • If you're at increased risk for severe illness, or you live with or spend time with someone at higher risk, in areas where the COVID-19 Community Level is medium and if advised by a health care practitioner to wear one

  • When sick and around other people

  • When caring for someone who has COVID-19

  • When on public transportation (for example, planes, buses, trains) and while indoors at transportation hubs (for example, airports, train stations) regardless of COVID-19 Community Level

In addition to being up to date with vaccinations and wearing a mask:

  • Get tested if you have symptoms of COVID-19

  • Avoid crowded places and indoor spaces that do not have fresh air from the outdoors, if you're at higher risk of getting very sick from COVID-19

  • Maintain good social distance (about 6 feet) from other people if you aren't up to date with vaccinations, especially if you're at higher risk of getting very sick with COVID-19

  • If possible, keep 6 feet away from a person who is sick with COVID-19

  • Wash your hands often with soap and water for at least 20 seconds

  • Use an alcohol-based hand sanitizer

  • Avoid touching your eyes, nose, and mouth with unwashed hands

  • Stay home when you're sick

  • Cover a cough or sneeze with a tissue, then throw the tissue in the trash

  • Clean and disinfect frequently touched objects and surfaces using a regular household cleaning spray or wipe

  • Pay attention to your health and watch for symptoms

What does it mean to quarantine or isolate?

To help prevent the virus from spreading, certain people should stay away from other people by quarantining or isolating. You need to isolate or quarantine if:

  • You have symptoms of COVID-19

  • You tested positive for COVID-19

  • You're a "close contact" of someone with COVID-19

You're a close contact if you were less than 6 feet away from an infected person for a total of 15 minutes or more over a 24-hour period (for example, three 5-minute exposures for a total of 15 minutes).

Quarantine is for people who are close contacts.

Quarantine for 5 days and use a mask for an additional 5 days (when you are with people who do not live in your household), if you are a "close contact" and

If a 5-day quarantine isn't possible, you must wear a well-fitting mask at all times when around others for 10 days after your exposure to the virus.

If you're up-to-date on your COVID-19 vaccine series (meaning you received your booster dose, if eligible), you don't need to quarantine after an exposure, but you should wear a mask for 10 days after the exposure.

Isolation is for people with COVID-19. If you were a close contact but then you got symptoms or tested positive, you need to isolate.

  • If you have COVID-19 (with or without symptoms), you should isolate for at least 5 days

  • The first day of symptoms and/or the day of the first positive test (if asymptomatic) is considered Day 0 of the infection

  • You can stop isolating after Day 5 if you don't have symptoms or if your symptoms are getting better (including that you don't have a fever and aren't taking drugs to lower a fever)

  • You must wear a well-fitting mask until Day 10, regardless of what day you stop isolating

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