What Is COVID-19?

What Is COVID-19?

Coronavirus, also known as COVID-19 is an infectious disease that affects the nose, throat, and lungs. It is caused by the SARS-CoV-2 virus. This virus belongs to the same family of viruses that cause the common cold, known as coronaviruses.

COVID-19 is very contagious. The SARS-CoV-2 virus was discovered in 2019, and COVID-19 quickly spread around the world. The World Health Organization declared a pandemic in March 2020.

The SARS-CoV-2 virus changes as it multiplies, producing related variants of the original strain. Variants cause similar signs and symptoms. On average, symptoms of COVID-19 appear about 5 days after exposure.

Signs & Symptoms of COVID-19


Signs and symptoms of COVID-19 develop between 2 and 14 days after a person is exposed to the virus. The time between infection and symptoms is known as the incubation period. COVID-19 symptoms can range from mild to severe. Older adults and people who have underlying medical conditions like heart or lung disease, or diabetes, are at higher risk for getting very sick.

Common COVID-19 symptoms include:

COVID-19 vs. flu

For the most part, the symptoms of COVID-19 and the flu are indistinguishable, and both can range from mild to severe illness. In addition, they both are spread between people in close contact. However, different viruses cause these two contagious respiratory illnesses: SARS-CoV2 causes COVID-19, and the influenza virus causes flu.

Here are some other differences between them:

  • COVID-19 generally spreads more easily than the flu and is more contagious.
  • After exposure, it may take longer for COVID-19 symptoms to develop (2-14 days) than flu symptoms (1-4 days).
  • Before symptoms develop, people infected with the COVID-19 virus can spread it for 2-3 days. Those with the flu begin to be contagious only 1 day before symptoms start.
  • Post-COVID-19 conditions, also called long COVID, can persist for weeks or months after infection, even in mild cases.

The only way to know whether you have COVID-19 or the flu is by performing a test with a nasal swab. If you have flu-like symptoms, take a home COVID-19 test as soon as symptoms start. This is an antigen test, available over-the-counter at pharmacies. If the result is negative, repeat the test after 48 hours to confirm. Early in the course of a COVID-19 infection, home tests may give a false negative result

What Causes COVID-19?


Infection with the SARS-CoV-2 virus causes COVID-19. The illness spreads easily among people in close contact (within 6 feet of each other). A person infected with the virus can spread it even before they have any symptoms.

COVID-19 can be transmitted when a the person with the virus coughs, sneezes or breathes out droplets or particles that contain the virus. Other people breathe them in, or the droplets land on the eyes, nose, or mouth of others.

Risk Factors for COVID-19

Risk Factors

A person’s risk of coming down with COVID-19 depends on the situation in which they were exposed and their individual health. The risk of getting sick is higher if:

  • The infected person you were exposed to had severe or mild symptoms.
  • You spent a long time (more than 15 minutes) near the infected person.
  • The infected person was coughing, singing, shouting, or breathing heavily.
  • Neither you nor the infected person was wearing a mask.
  • You were in a poorly ventilated room.
  • You were very close to, or touching, the infected person.

People with certain preexisting medical conditions or risk factors are more likely to become severely ill than others if they contract COVID-19. A primary care doctor or pediatrician can help with managing conditions that increase the chances of developing severe symptoms of COVID-19. Risk factors include:



Some people who contract COVID-19 experience a long illness and a wide range of ongoing health problems. Serious complications that can result from COVID-19 include:

COVID-19 Prevention


There are many steps you can take to avoid getting sick with COVID-19. These actions also protect others in your family and community:

  • Get vaccinated. COVID-19 vaccines are recommended for everyone 6 months and older. Stay up to date with booster shots.
  • Wash your hands frequently.
  • Avoid touching your face, eyes, nose, and mouth.
  • Wear a mask in indoor public spaces.
  • Practice social distancing, staying 6 feet from others in public spaces.
  • Avoid contact with people who are sick or known to have COVID-19.
  • Improve indoor ventilation or air filtering when possible.
  • Move group activities outdoors.
  • Stay home if you are feeling sick or experiencing COVID-19 symptoms.

COVID-19 vaccines

COVID-19 vaccines available in the United States are safe and effective. When vaccines and boosters are taken according to recommendations, they help protect against COVID-19 infection, as well as serious illness, hospitalization, and death, if a person does become infected. There are currently four approved or authorized COVID-19 vaccines:

  • Pfizer-BioNTech
  • Moderna
  • Novavax
  • J&J/Janssen

Consult the Centers for Disease Control for up-to-date guidelines on which vaccine or booster shot to get, based on your age, your previous vaccines, and other considerations.

Get Care

Trust NewYork-Presbyterian for COVID-19

Schedule an appointment or video visit* with a NewYork-Presbyterian primary care doctor if you have mild or severe COVID-19 symptoms. Our experienced physicians can provide up-to-date advice on testing and treatment options. We offer same-day appointments for critical needs and easy scheduling with early, late, and weekend hours.

*Restrictions apply