Coronavirus, COVID-19


What is coronavirus?

Coronaviruses are a family of viruses that can cause respiratory illness in humans. They are called “corona” because of crown-like spikes on the surface of the virus. Severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS) and the common cold are examples of coronaviruses that cause illness in humans.

The new strain of coronavirus — COVID-19 — was first reported in Wuhan, China in December 2019. The virus has since spread to all continents.

How many people are infected with COVID-19?

The number of people infected changes daily. As of this writing (10/11/2021), more than 196,910,000 people in the world have been infected. Over 4,850,000 people have died. Some 192 countries and territories on all continents have now reported cases of COVID-19.

How do you get infected with COVID-19?

COVID-19 enters your body through your mouth, nose or eyes (directly from the airborne droplets or from transfer of the virus from your hands to your face). The virus travels to the back of your nasal passages and mucous membrane in the back of your throat. It attaches to cells there, begins to multiply and moves into lung tissue. From there, the virus can spread to other body tissues.

How does the new coronavirus (COVID-19) spread from person to person?

COVID-19 is likely spread:

  • The virus travels in respiratory droplets released into the air when an infected person coughs, sneezes, talks, sings or breathes near you (within 6 feet). You may be infected if you inhale these droplets.
  • You can also get COVID-19 from close contact (touching, shaking hands) with an infected person and then touching your face.
  • It’s considered possible to get COVID-19 after touching a contaminated surface and then touching your eyes, mouth, or nose before washing your hands. But it’s thought to be unlikely.

Where do coronaviruses come from?

Coronaviruses are often found in bats, cats and camels. The viruses live in but do not infect the animals. Sometimes these viruses then spread to different animal species. The viruses may change (mutate) as they transfer to other species. Eventually, the virus can jump from animal species and begins to infect humans. In the case of COVID-19, the first people infected in Wuhan, China are thought to have contracted the virus at a food market that sold meat, fish and live animals. Although researchers don’t know exactly how people were infected, they already have evidence that the virus can be spread directly from person to person through close contact.

What’s different about the delta variant of COVID-19?

It’s normal for viruses to mutate — especially coronaviruses and influenza viruses. These mutations create new variants of the virus. Sometimes the variants are less contagious, less severe or have slightly different presenting symptoms. Unfortunately, the delta variant of COVID-19 (a strain called B.1.617.2) is more highly contagious and more likely to result in severe illness.

How long is a person infected with COVID-19 considered contagious?

If you’re infected with COVID-19 it can take several days to develop symptoms — but you are contagious during this time. You are no longer contagious 10 days after your symptoms began.

The best way to avoid spreading COVID-19 to others is to:

  • Stay 6 feet away from others whenever possible.
  • Wear a cloth mask that covers your mouth and nose when around others.
  • Wash your hands often. If soap is not available, use a hand sanitizer that contains at least 60% alcohol.
  • Avoid crowded indoor spaces. Bring in outdoor air as much as possible.
  • Stay self-isolated at home if you are feeling ill with symptoms that could be COVID-19 or have a positive test for COVID-19.
  • Clean and disinfect frequently touched surfaces.

How soon after becoming infected with COVID-19 will I develop symptoms?

The time between becoming infected and showing symptoms (incubation period) can range from 2 to 14 days. The average time before experiencing symptoms is five days. Symptoms can range in severity from very mild to severe. In about 80% of patients, COVID-19 causes only mild symptoms, although this may change as variants emerge.

Who’s most at risk for getting COVID-19?

Persons at greatest risk of contracting COVID-19 are:

  • People who live in or have recently traveled to any area with ongoing active spread.
  • People who have had close contact with a person who has a laboratory-confirmed or a suspected case of the COVID-19 virus. Close contact is defined as being within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period.
  • People over age 60 who have pre-existing medical conditions or a weakened immune system.

Have certain ethnic groups been harder hit by COVID-19?

Yes. Many researchers have analyzed data across the country and in some large cities, looking at number of confirmed cases and deaths based on race and ethnicity and related factors. They found that African Americans and the Latino-Hispanic populations have disproportionately higher rates of hospitalizations and deaths due to COVID-19.

Researchers suspect this might be because these ethnic groups tend to:

  • Live in more crowded housing situations — living in densely populated areas and in multi-generational households — making social distancing practices difficult.
  • Work in consumer-facing service industries and are more likely to use public transportation to get to work, putting them at risk for increased exposure to COVID-19.
  • Be at increased risk of severe illness if they get COVID-19 because of higher rates of existing medical conditions, such as high blood pressure, diabetes, obesity, asthma, and heart, liver and kidney diseases.
  • Be more likely to be uninsured or lack a consistent care source, which limits access to COVID-19 testing and treatment services.

Researchers are still studying other factors that may make ethnic groups more susceptible to negative COVID-19 outcomes, including:

  • Genetics.
  • Possible differences in lung tissue.
  • Socioeconomic status.

If I recover from a case of COVID-19, can I be infected again?

Reinfection with COVID-19 is rare, but has been reported.

Symptoms and Causes

What are the symptoms of the novel coronavirus (COVID-19) infection?

The CDC says you may have coronavirus if you have these symptoms or a combination of symptoms:

  • Fever or chills.
  • Cough.
  • Shortness of breath or difficulty breathing.
  • Tiredness.
  • Muscle or body aches.
  • Headaches.
  • New loss of taste or smell.
  • Sore throat.
  • Congestion or runny nose.
  • Nausea or vomiting.
  • Diarrhea.

Additional symptoms are possible.

Symptoms may appear between two and 14 days after exposure to the virus. Children have similar, but usually milder, symptoms than adults. Older adults and people who have severe underlying medical conditions like heart or lung disease or diabetes are at higher risk of more serious complication from COVID-19.

Call 911 and get immediate medical attention if you have these warning signs

  • Trouble breathing.
  • Persistent pain or pressure in your chest.
  • New confusion.
  • Inability to wake up from sleep.
  • Bluish lips or face.

This list does not include all possible symptoms. Contact your healthcare provider if you are concerned you may have coronavirus or have any severe symptoms.

Diagnosis and Tests

How is coronavirus diagnosed?

COVID-19 is diagnosed with a laboratory test. Your healthcare provider may collect a sample of your saliva or swab your nose or throat to send for testing.

When should I be tested for the coronavirus (COVID-19)?

Call your healthcare provider if you:

  • Feel sick with fever, cough or have difficulty breathing.
  • Have been in close contact with a person known or suspected to have COVID-19.

Your healthcare provider will ask you questions about your symptoms. Your healthcare provider will tell you if you need to be tested for COVID-19.

If I have a positive test for coronavirus, how long should I self-isolate?

According to current CDC recommendations, you should self-isolate until you've met all three of the following criteria:

  • It's been 10 days since your symptoms first appeared.
  • You've not had a fever for 24 hours and you've not used fever-lowing medications during this time.
  • Your COVID-19 symptoms have improved.

While at home, ideally self-isolate within separate room of your home if possible to limit interaction with other family members. If you can’t stay 100% isolated in a separate room, keep 6 feet away from others and wear a cloth mask, wash your hands often/family members wash hands often, and frequently disinfect commonly touched surfaces and shared areas.

You don't need to be retested to be around others outside your home. However, since everyone and every case is unique, follow your healthcare provider's recommendations for testing.

If you have a weakened immune system or have had a severe case of COVID-19, the CDC's criteria do not apply to you. You may need to stay home for up to 20 days after your symptoms first appeared. Talk with your healthcare provider about your situation.

How long do I need to isolate myself if I’ve been around a person with COVID-19?

Known contacts that have not yet been fully vaccinated should quarantine for an appropriate time from the date of exposure based on local guidance. This is typically 14 days, but can vary with testing and concerns around variant strains.

  • Fully vaccinated individuals who meet the following criteria are not required to quarantine:
  • They are fully vaccinated (2 weeks have passed since the second dose in a 2-dose series, or 2 weeks after their dose in a single-dose vaccine).
  • They are within 3 months following the last vaccine dose in the series.
  • They remain asymptomatic since their current exposure to COVID-19. Fully vaccinated people should still self-monitor for symptoms of COVID-19 for 14 days following exposure, and seek clinical evaluation if indicated.

Is it possible to test negative for COVID-19 and still be infected with the virus?

Yes, it’s possible. There are several reasons for “false negative” test results — meaning you really DO have COVID-19 although the test result says you don’t.

Reasons for a false negative COVID-19 test result include:

  • You were tested too early in the course of illness. The virus hasn’t multiplied in your body to the level that it could be detected by the test.
  • They didn’t get a good specimen. The healthcare personnel may not have swabbed deeply enough in the nasal cavity to collect a good sample. There could also be handling errors and transportation errors.
  • The COVID-19 test itself was not sensitive or specific enough to detect COVID-19. Sensitivity refers to the ability of the test to detect the smallest amount of virus. Specificity refers to the ability of the test to detect only the COVID-19 virus and not other similar viruses. Many different commercial and hospital laboratories have developed tests for COVID-19. All must meet standards, but no test is 100% sensitive and 100% specific for COVID-19. This is why there is always a possibility of “false negative” and “false positive” tests.

If you think you might have COVID-19 even if your test is negative, it’s best to follow the current CDC recommendations. Stay home for 10 days if you think you are sick. Stay 6 feet away from others (“social distancing”) and wear a cloth mask. Contact your healthcare provider if your symptoms worsen. Don’t decide on your own if it’s safe for you to be around others. Instead, contact your healthcare provider when your symptoms improve.

Management and Treatment

What medications are currently approved to treat COVID-19?

Currently, only one drug has received Food and Drug Administration (FDA) approval. Remdesivir (Veklury®) is approved to treat hospitalized patients with COVID-19 infection.

What treatments do people receive if they have COVID-19?

Treatments for COVID-19 vary depending on the severity of your symptoms. If you’re not in the hospital or don’t need supplemental oxygen, no specific antiviral or immunotherapy is recommended. Some people may also benefit from an infusion of monoclonal antibodies.

But if you’re in the hospital, you may be given IV remdesivir with or without the oral (by mouth) corticosteroid dexamethasone (or another steroid) or dexamethasone alone if remdesivir can’t be used.

Depending on the severity of your COVID infection, you may need:

  • Supplemental oxygen (given through tubing inserted into your nostrils).
  • Mechanical ventilation (receive oxygen through a tube inserted down your trachea). You are given medications to keep you comfortable and sleepy as long as you’re receiving oxygen through a ventilator.
  • Extracorporeal membrane oxygenation (ECMO). You continue to receive treatment while a machine pumps your blood outside your body. It takes over the function of your body’s lungs and heart.

What vaccines are in use or in late-stage development to prevent COVID-19?

The Food and Drug Administration has granted Emergency Use Authorization for three coronavirus vaccines. Both the Pfizer and Moderna vaccines are administered in two doses. It’s important for you to get both doses of the vaccine for maximum protection. Pfizer’s vaccine doses are given 21 days apart and it’s authorized for use in those age 5 and older. Doses of the Moderna vaccine are given 28 days apart, and it’s authorized for use in those age 18 and older. Both vaccines are highly effective. Another effective option is Johnson & Johnson’s single-dose vaccine, which is authorized for use in individuals 18 years of age and older.

Can vaccinated people still get COVID-19?

No vaccines are 100% effective. In fact, breakthrough cases (when someone tests positive for COVID-19 more than two weeks after they're fully vaccinated) are expected. The vaccines reduce your risk of infection. The risk of a severe illness or death from a breakthrough infection is extremely low.

If I’ve tested positive for COVID-19 and do not need hospitalization, what can I do to best manage my symptoms at home?

If you have mild COVID-19 symptoms, you will likely need to manage your health at home. Follow these tips:

  • If you have a fever, drink plenty of fluids (water is best), get lots of rest, take acetaminophen (Tylenol®).
  • If you have a cough, lie on your side or sit up (don’t lie on your back). Add a teaspoon of honey to your hot tea or hot water (don’t give honey to children under one year old). Gargle with salt water. Call your healthcare provider or pharmacist for advice about over-the-counter, comfort care product, like cough suppressants, cough drops/lozenges. Have a friend or family member pick up any needed medicines. You must stay at home.
  • If you are anxious about your breathing, try to relax. Take slow deep breaths in through your nose and slowly release through pursed lips (like you’re are slowly blowing out a candle). If you are having trouble breathing, call 911.

If you have a mild case of COVID-19, you should start to feel better in a few days to a week. If you think your symptoms are getting worse, call your healthcare provider.


How can I prevent getting the novel coronavirus (COVID-19)?

The best defense to prevent getting COVID-19 is to get vaccinated. You should also follow the same steps you would take to prevent getting other viruses, such as the common cold or the flu.

  • Wash your hands for at least 20 seconds— especially before eating and preparing food, after using the bathroom, after wiping your nose, and after coming in contact with someone who has a cold.
  • Wear a multilayered cloth facemask that fits snugly on your face and covers your mouth, nose and chin.
  • Avoid touching your eyes, nose and mouth to prevent the spread of viruses from your hands.
  • Cover your mouth and nose with a tissue when sneezing and coughing or sneeze and cough into your sleeve. Throw the tissue in the trash. Wash your hands afterward. Never cough or sneeze into your hands!
  • Avoid close contact (within 6 feet) with those who have coughs, colds or are sick. Stay home if you are sick.
  • If you are prone to sickness or have a weakened immune system, stay away from large crowds of people. Follow the directions of your healthcare authorities especially during outbreaks.
  • Clean frequently used surfaces (such as doorknobs and countertops) with a virus-killing disinfectant.
  • Use hand sanitizers that contain at least 60% alcohol if soap and water are not available.
  • Greet people with a friendly gesture instead of shaking hands.
  • Get enough sleep, eat a healthy diet, drink plenty of liquids and exercise if you are able. These steps will strengthen your immune system and enable you to fight off infections easier.

Should I wear a face mask?

The CDC recommends wearing a cloth face coverings in public, especially in places where it’s hard to maintain at least six feet of distance between yourself and another person. Face masks protect both you and the people around you. Cloth face masks are being recommended because we now know individuals with COVID-19 could have mild or no symptoms, while still spreading the virus to others.

A note from Cleveland Clinic

We’ve come a long way since the first cases of coronavirus (COVID-19) were confirmed in the United States. We’ve learned a lot about the virus and how to treat patients who have it. We’ve also greatly increased our ability for testing. You — our communities — have made tremendous efforts to adapt, too. It’s heartening to see so many people protecting each other by wearing face masks in public and finding ways to have fun while respecting the rules of social distancing.

The changes we’ve all made to stay safe and healthy can feel challenging. But please stay vigilant. We know it’s not easy, but it’s critical. COVID-19 shouldn't be taken lightly. While most people get only mild symptoms, others develop serious complications of the lungs, brain and heart. There may also be other long-term effects that we don’t yet know about. And, so far, there’s no cure. Fortunately, there are steps we can all take to prevent this. But for them to be effective, we all need to do them all of the time.

Last reviewed by a Cleveland Clinic medical professional on 11/04/2021.


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