What Is Coronavirus? | Johns Hopkins Medicine

Infectious Diseases

Updated on February 24, 2022

Coronaviruses are a type of virus. There are many different kinds, and some cause disease. A coronavirus identified in 2019, SARS-CoV-2, has caused a pandemic of respiratory illness, called COVID-19.

As of now, researchers know that the coronavirus is spread through droplets and virus particles released into the air when an infected person breathes, talks, laughs, sings, coughs or sneezes. Larger droplets may fall to the ground in a few seconds, but tiny infectious particles can linger in the air and accumulate in indoor places, especially where many people are gathered and there is poor ventilation. This is why mask-wearing, hand hygiene and physical distancing are essential to preventing COVID-19.

The first case of COVID-19 was reported Dec. 1, 2019, and the cause was a then-new coronavirus later named SARS-CoV-2. SARS-CoV-2 may have originated in an animal and changed (mutated) so it could cause illness in humans. In the past, several infectious disease outbreaks have been traced to viruses originating in birds, pigs, bats and other animals that mutated to become dangerous to humans. Research continues, and more study may reveal how and why the coronavirus evolved to cause pandemic disease.

Symptoms show up in people within two to 14 days of exposure to the virus. A person infected with the coronavirus is contagious to others for up to two days before symptoms appear, and they remain contagious to others for 10 to 20 days, depending upon their immune system and the severity of their illness.

Infectious disease expert Lisa Maragakis explains the advances in COVID-19 treatments and how knowledge of COVID-19 can assist in preventing further spread of the virus.

COVID-19 symptoms include:

Some people infected with the coronavirus have mild COVID-19 illness, and others have no symptoms at all. In some cases, however, COVID-19 can lead to respiratory failure, lastinglungandheart muscle damage,nervous system problems,kidney failureor death.

If you have a fever or any of the symptoms listed above, call your doctor or a health care provider and explain your symptoms over the phone before going to the doctors office, urgent care facility or emergency room. Here are suggestionsif you feel sick and are concerned you might have COVID-19.

CALL 911 if you have a medical emergency such as severe shortness of breath or difficulty breathing.

Learn more about COVID-19 symptoms.

COVID-19 is diagnosed through a test. Diagnosis by examination alone is difficult since many COVID-19 signs and symptoms can be caused by other illnesses. Some people with the coronavirus do not have symptoms at all.Learn more about COVID-19 testing.

Treatment for COVID-19 depends on the severity of the infection. For milder illness, resting at home and taking medicine to reduce fever is often sufficient. More severe cases may require hospitalization, with treatment that might include intravenous medications, supplemental oxygen, assisted ventilation and other supportive measures

Two COVID-19 vaccines Pfizer and Moderna - have been fully approved by the FDA and recommended by the CDC as highly effective in preventing serious disease, hospitalization and death from COVID-19.

The CDC notes that in most situations the two mRNA vaccines from Pfizer and Moderna are preferred over the Johnson & Johnson vaccine due to a risk of serious adverse events. The J&J vaccine may be available for those who yet prefer it and for use in certain circumstances.

It is also important to receive a booster when you are eligible. You can get any of these three authorized or approved vaccines, but the CDC explains that Pfizer and Moderna are preferred in most situations.

In addition, it helps to keep up with other safety precautions, such as following testing guidelines, wearing a mask, washing your hands and practicing physical distancing.

Yes, severe COVID-19 can be fatal. For updates of coronavirus infections, deaths and vaccinations worldwide, see theCoronavirus COVID-19 Global Casesmap developed by the Johns Hopkins Center for Systems Science and Engineering.

Two COVID-19 vaccines Pfizer and Moderna - have been fully approved by the FDA and recommended by the CDC as highly effective in preventing serious disease, hospitalization and death from COVID-19.

The CDC notes that in most situations the two mRNA vaccines from Pfizer and Moderna are preferred over the Johnson & Johnson vaccine due to a risk of serious adverse events. The J&J vaccine may be available for those who yet prefer it and for use in certain circumstances.

It is also important to receive a booster when eligible. You can get any of these three authorized or approved vaccines, but the CDC explains that Pfizer and Moderna are preferred in most situations.

Coronaviruses are named for their appearance: corona means crown. The viruss outer layers are covered with spike proteins that surround them like a crown.

SARSstands for severe acute respiratory syndrome. In 2003, an outbreak of SARS affected people in several countries before ending in 2004. The coronavirus that causes COVID-19 is similar to the one that caused the 2003 SARS outbreak.

Since the 2019 coronavirus is related to the original coronavirus that caused SARS and can also cause severe acute respiratory syndrome, there is SARS in its name: SARS-CoV-2. Much is still unknown about these viruses, but SARS-CoV-2 spreads faster and farther than the 2003 SARS-CoV-1 virus. This is likely because of how easily it is transmitted person to person, even from asymptomatic carriers of the virus.

Yes, there are different variants of this coronavirus. Like other viruses, the coronavirus that causes COVID-19 can change (mutate). Mutations may enable the coronavirus to spread faster from person to person as in the case of the delta and omicron variants. More infections can result in more people getting very sick and also create more opportunity for the virus to develop further mutations. Read more aboutcoronavirus variants.

If you are concerned that you may have COVID-19, follow these steps to help protect your health and the health of others.

What you need to know from Johns Hopkins Medicine.

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What Is Coronavirus? | Johns Hopkins Medicine