What is the novel coronavirus (COVID-19)?

This article was last reviewed on October 12, 2021.

Coronavirus disease 2019 (COVID-19) is caused by a coronavirus called SARS-CoV-2. A coronavirus is a type of virus that causes respiratory tract infections, such as colds and pneumonia. Although coronaviruses usually cause mild symptoms, they can (on rare occasions) cause life-threatening breathing difficulties and death.

Where did the disease originate?

Coronaviruses are common among animals. They’re ‘zoonotic,’ meaning that they can be spread between humans and animals. The reservoir — where microbes such as viruses live and grow — for COVID-19 appears to be bats. Research into where the infection started is ongoing, but a major source of the outbreak has been traced to a large seafood and meat market in Wuhan City, China. Due to the ability of the virus to spread from person to person so easily, it has since been declared a pandemic.

How does COVID-19 spread?

COVID-19 is mainly spread:1

  • By inhaling respiratory droplets produced when an infected person coughs or sneezes
  • When droplets or particles that contain the virus land on the mouth, nose or eyes when an infected person coughs or sneezes
  • When someone touches their mouth, nose, or eyes with unwashed hands that have the virus on them

You are at highest risk if you are in direct contact or physically close (within 6 feet for a total of 15 minutes or more) to someone that has COVID-19.

To protect yourself:

  • Get a COVID-19 vaccine as soon as you can
  • Wear a mask that covers your nose and mouth when you are around people not in your immediate household and in public settings. Masks protect the wearer as well as others they may come in contact with
  • Wash your hands
  • Stay 6 feet apart, avoid crowds and poorly ventilated spaces


Viruses constantly change (mutate) and new variants occur. Some of these variants disappear and others continue to spread. There are many variants of COVID-19 that are being tracked in the US and worldwide.

What do we know about the Delta variant2:

  • The Delta variant is more contagious than previous variants
  • There is some data showing that the Delta variant causes more severe illness in unvaccinated people than previous strains
  • COVID-19 tests are able to detect all the variants but cannot tell you which variant
  • The FDA-authorized vaccines are highly effective at preventing severe illness and death against the known variants including Delta
  • Fully vaccinated people that are infected with Delta variant are able to spread the virus to others but they are infectious for a shorter period of time than unvaccinated people

With what is known about the Delta variant, it is important to get vaccinated, mask indoors in public spaces and follow proper hygiene to reduce the spread.

The information provided is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Seek the advice of a doctor with any questions you may have regarding a medical condition. Never delay seeking or disregard professional medical advice because of something you have read here.