What is the new coronavirus?

The novel coronavirus, which emerged in China in late 2019, can cause a potentially fatal lung disease known as COVID-19. While a majority of people who contract the virus will have mild illness, others develop severe lung disease, which may include pneumonia and respiratory failure that requires a mechanical ventilator.

How is the coronavirus transmitted?

The coronavirus (officially known as SARS-CoV-2) mainly spreads through respiratory droplets released when a person with the virus coughs or sneezes. The virus can be transmitted through the air or when the virus lands on surfaces and someone touches these surfaces and then transfers it to their mouth, nose or eyes.

The coronavirus is detectable in the stool, but fecal spread is thought to be uncommon. Mother-to-child transmission has not been reported among women who were pregnant when they contracted the virus, and it has not been found in breast milk.

How can transmission be prevented?

Several precautions can reduce transmission of the new coronavirus, many of them similar to those recommended to prevent seasonal flu: 

  • Avoid close contact—meaning within six feet—with people who are ill.
  • Wash your hands with soap and water frequently and thoroughly for at least 20 seconds.
  • Use hand sanitizer containing at least 60% alcohol if soap and water are not available.
  • Avoid touching your face, especially your mouth, nose and eyes.
  • Clean and disinfect surfaces that are frequently touched, such as doorknobs.
  • Stay home if you are sick.
  • Cough or sneeze into a tissue or your elbow, and immediately dispose of tissues in the trash.
  • Healthy people do not need to routinely wear face masks, but use a mask if you are ill or caring for someone who is ill.
  • Get vaccinated against the flu and pneumonia. 

More stringent prevention measures may be implemented in areas where the virus is spreading. These include “social distancing,” such as avoiding close contact with people outside your household, staying away from public gatherings, working from home and closing schools. Quarantine is a stricter approach that requires people who might have been exposed to the virus to stay at home or in another designated location for a certain period of time. Isolation practices, including the use of personal protective equipment, are used when caring for a person with COVID-19 in the hospital.

It is not yet certain whether people who contract the new coronavirus and recover develop protective immunity that can prevent future infections, or, if so, how long this might last.

There is currently no vaccine for the coronavirus, although several experimental vaccine candidates are now in clinical trials. Experts predict that a safe and effective vaccine will not be available for at least 12 to 18 months, in other words, between March and September 2021.

Who is at risk for COVID-19?

While anyone can catch the new coronavirus, certain groups are at greater risk of developing more severe illness: 

  • People age 60 or older
  • People with compromised immune systems
  • People with preexisting health conditions, including cardiovascular disease, chronic lung disease, high blood pressure (hypertension) or diabetes. 

While older people and those with other health conditions are more likely to develop severe disease, young and healthy people can also become seriously ill. Although children seldom develop severe disease, they can carry the virus and transmit it to others.

People with HIV who are on effective antiretroviral treatment and have a high CD4 cell count are probably not much more likely to contract the coronavirus or develop severe COVID-19, experts say. However, those who have unsuppressed HIV, currently have a low CD4 count or had a very low CD4 count in the past may be at greater risk.

People with cancer who are being treated with chemotherapy and those who have undergone bone marrow transplants often have weakened immune systems and are prone to infections. Not much is known yet about how COVID-19 affects people living with cancer. 

What are the symptoms of COVID-19?

Around 80% of people with COVID-19 have mild or moderate illness and will recover without special treatment. About 15% will develop severe respiratory problems, and about 5% of cases are critical or life-threatening.

Some people who contract the coronavirus have few or no symptoms but can still transmit the virus to others. The most common early symptoms of COVID-19 are fever, cough, fatigue and shortness of breath. A range of other symptoms have been reported, including sore throat, nasal congestion, body aches, loss of the sense of smell and diarrhea. It takes around five days, on average, between exposure to the virus and the appearance of symptoms.

As the disease progresses, people may find it increasingly difficult to breathe. In serious cases, they may develop pneumonia, in which air sacs in the lungs (alveoli) fill with fluid, preventing oxygen from entering the bloodstream. In the most severe cases, patients can develop acute respiratory distress syndrome (widespread lung inflammation that requires mechanical ventilation). Both the virus itself and the immune system’s response to it can damage the lungs. Some people with severe COVID-19 experience an immune overreaction known as a cytokine storm than can lead to organ failure.

The COVID-19 mortality rate is not yet known because, due to limited testing, it is uncertain how many people have contracted the virus. Most experts expect the overall mortality rate will be around 1%, or about 10 times higher than that of a typical seasonal flu.

How is the coronavirus diagnosed?

The coronavirus can be diagnosed using a PCR RNA test that detects viral genetic material in a nasal swab sample. Testing positive indicates current active infection. These tests are in limited supply, and in some areas, they are reserved for people with suspected exposure or severe symptoms.

Another type of test measures antibodies to the coronavirus in the blood, which can reveal whether someone was infected in the past and has developed immunity. Antibody tests (also known as serology tests) are not yet widely available.

If you think you may have been exposed to the coronavirus, contact a health care provider if you develop a fever, cough or difficulty breathing. Before you go to a clinic or hospital, call ahead so the staff can give you instructions and take appropriate precautions.


How is COVID-19 treated?

People with mild or moderate symptoms can usually receive supportive care at home, similar to care for the flu. This may include taking over-the-counter medications to manage fever and cough, drinking plenty or fluids, using a humidifier and getting adequate rest.

In more severe cases, a person with COVID-19 may require hospitalization for more intensive care. This may involve breathing supplemental oxygen or, if patients can’t breathe on their own, the use of a ventilator machine.

There are currently no approved treatments for COVID-19. Several drugs have shown activity against SARS-CoV-2 or related coronaviruses, and some appear to have helped patients in specific cases. Some of these medications are already approved to treat other conditions, such as HIV or malaria, and others are new experimental drugs. Clinical trials must be done to determine whether potential therapies are safe and effective enough for wide use.

Last Reviewed: March 25, 2020