What is coronavirus?

Coronaviruses are a family of viruses that can cause respiratory illness in humans. They get their name, “corona,” from the many 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 (except Antarctica).

How many people are infected with COVID-19?

The number of people infected changes daily. Organizations that collect this information, including the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), are gathering information and continuously learning more about this outbreak. As of this writing (10/22/2020), more than 41,000,000 people in the world have been infected. Over 1,100,000 people have died. Some 189 countries and territories on all continents (except Antartica) have now reported cases of COVID-19. The U.S. has the highest number of cases, with more than 8,300,000 people infected and over 220,000 deaths. India has over 7,700,000 cases; Brazil has more than 5,200,000 cases; Russia has more than 1,400,000 cases; Spain, France and Argentina have over 1,000,000 cases; Mexico and Peru have close to 900,000; England has nearly 800,000 cases and South Africa has over 700,000 cases. For the latest statistics, see the World Health Organization's situation reports and Johns Hopkins Coronavirus Resource Center map references at end of article.

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

COVID-19 is likely spread:

  • When the virus travels in respiratory droplets when an infected person coughs, sneezes, talks, sings or breathes near you (within six feet). This is thought to be the main way COVID-19 is spread.
  • When the virus travels in small respiratory droplets that linger in the air for minutes to hours from an infected person who is more than six feet away or has since left the space. This method of spread is more likely to occur in enclosed spaces with poor ventilation.
  • From close contact (touching, shaking hands) with an infected person.
  • By touching surfaces that the virus has landed on, then touching your eyes, mouth, or nose before washing your hands. (Not thought to spread easily by this method.)

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.

Governments, health agencies, researchers and healthcare providers are all working together to develop policies and procedures to limit the spread of this virus both globally and from individual to individual.

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

Researchers are still learning about COVID-19. What IS known is that people infected with COVID-19 can spread the virus to others before experiencing symptoms themselves (while people are still “asymptomatic”). Once you do have symptoms, the CDC says you are no longer contagious 10 days after your symptoms began.

Until everything about COVID-19 is fully understood, the best advice from healthcare providers to remain safe is to:

  • Stay six 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?

This so-called “incubation period,” the time between becoming infected and showing symptoms, can range from two 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.

Who is 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 six 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 been analyzing 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. What they found is that African Americans and the Latino-Hispanic populations have disproportionate higher rates of hospitalizations and deaths due to COVID-19.

There are several reasons why researchers suspect these populations are more affected. They believe 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 and possible differences in lung tissue as well as socioeconomic status and the social environment and systems.

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

The U.S. Centers for Disease Control says that "the immune response to COVID-19 is not yet understood." Because this is a new strain of coronavirus, scientists are still collecting information and research on the virus so it's still too early to know if you can get it a second time if you've had it once.

In a related theme, scientists are seeing a subset of patients who have COVID-19 and have symptoms that continue off and on for weeks and even months. These patients are called coronavirus long haulers. Scientists continue to follow these patients.

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 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 arouse (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 coronavirus, have other symptoms 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 the novel coronavirus, COVID-19 and where to go to be tested.

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, stay six 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?

According to the CDC, if you’ve been in close contact with a person who has COVID-19, you should stay home for 14 days after you’ve last seen this person. You don’t need to stay home if the person has had COVID-19 symptoms within the last three months and they have completely recovered and have remained symptom-free.

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

Yes. This is 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.
  • A good specimen was not obtained. 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, as the sample must be transported to a lab to be tested.
  • 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 recommendation. Stay home for 10 days if you think you are sick. Stay six feet away from others (“social distancing”) and wear a cloth mask. Contact your healthcare provider if your symptoms worsen. Contact your healthcare provider when your symptoms improve – don’t decide on your own if it’s safe for you to be around others.

Management and Treatment

How is COVID-19 treated?

Current ways to manage COVID-19 include using the same support care (e.g., rest, fluids, fever control) and preventive measures used to treat other coronaviruses such as a cold.

At the moment, there is no cure for COVID-19. Scientists are currently developing several vaccines, which are now being tested large numbers of people. There are several stages to vaccine testing in humans, each of which normally would take many months to years to complete. Because this is a global pandemic, scientists from all over the world are racing to develop a safe and effective vaccine in as short a time frame as possible.

There are no drugs specifically approved to treat COVID-19. Some drugs already approved in the U.S. for other medical conditions are beginning to be given -- as a trial -- to patients infected with COVID-19. These drugs include and the antibiotic azithromycin. The FDA recently granted an emergency use authorization for the investigational antiviral, remdesivir, for hospitalized patients with severe disease. The drug has been shown to shorten the recovery time in some patients. Many other anti-inflammatory, antiviral drugs and other drugs are being studied. The corticosteroid dexamethasone is being studied to treat or prevent lung injury from inflammation.

Convalescent plasma, blood donated from people who have had COVID-19, is also being tested as a treatment in people with severe illness.

The Food and Drug Administration had authorized emergency use of hydroxycholoroquine (approved to treat malaria, lupus and arthritis) and chloroquine (approved to treat malaria) to treat COVID-19 but has since retracted this authorization. More information showed the drugs were unlikely to be effective and and also could cause heart rhythm disturbances.


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

Right now, the best defense to prevent getting COVID-19 is to follow some of 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.
  • 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 six 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 counter tops) 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. 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.

The cloth face coverings recommended by the CDC are not surgical masks or N-95 respirators, which should be reserved for healthcare workers and first responders.


Where can I learn more about COVID-19?

Additional Information

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.

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