This article was updated on April 29, 2020 to include additional symptoms of the 2019 coronavirus.

The term “coronavirus” refers to a large group of viruses known to affect birds and mammals, including humans. COVID-19, which first appeared in China in December 2019, is a type of coronavirus.

Coronaviruses are named for the spiky projections on their surface. These resemble the points on a crown. Corona means “crown” in Latin.

There are hundreds of coronaviruses, but only seven are known to affect people. Four human coronaviruses only cause mild cold- or flu-like symptoms. Three other coronaviruses pose more serious risks.

Keep reading to learn more about the types of coronaviruses, including COVID-19.

All seven types of human coronaviruses cause upper respiratory infections. Symptoms resemble those of the common cold or flu and may include:

  • nasal congestion
  • sore throat
  • cough
  • headaches
  • fever

According to the Centers for Disease Control and Prevention (CDC), coronaviruses occasionally cause complications in the lower respiratory tract, such as pneumonia.

These complications are more common among:

  • infants
  • older adults
  • people with other illnesses or weakened immune systems

The seven coronaviruses that affect humans can be categorized into two groups.

Common human coronaviruses

There are four common human coronaviruses:

  • 229E
  • NL63
  • OC43
  • HKU1

Common human coronaviruses usually cause mild to moderate symptoms.

Most people around the world will develop at least one of these viral infections over their lifetime. Those who contract these viruses are able to recover on their own most of the time.

Other human coronaviruses

Three additional coronaviruses originated as animal infections. Over time, these viruses evolved and were eventually transmitted to humans.

These coronaviruses pose more serious risks to human health. They’re described below.

SARS-CoV

SARS-CoV causes Severe Acute Respiratory Syndrome (SARS). According to the World Health Organization (WHO), the first human cases appeared in southern China in November 2002.

SARS-CoV may have originated in bats and were transmitted to other animals before infecting humans.

During the 2002-2003 epidemic, more than 8,000 people in 26 countries around the world contracted SARS. There were 774 reported deaths.

The outbreak was contained in mid-2003 with the implementation of infection control practices such as isolation and quarantine. Since then, a handful of cases have occurred due to laboratory accidents.

There are currently no reported cases of SARS transmission in the world. However, if the virus re-emerges, it could pose a significant threat to the public.

MERS-CoV

MERS-CoV causes Middle East Respiratory Syndrome (MERS). According to WHO, it emerged in September 2012 in Saudi Arabia, although initial cases were later traced back to Jordan.

Humans contract MERS-CoV through contact with camels that have contracted the infection. The virus is also transmitted by coming into very close contact with a person who has the infection.

Since 2012, 27 countries have reported more than 2,400 MERS cases. To date, the majority of cases have occurred in Saudi Arabia.

In 2015, an outbreak in South Korea led to 186 cases and 36 deaths. According to the CDC, this outbreak originated with a traveler returning from the Middle East.

According to the European Center for Disease Prevention and Control (ECDPC), there were more than 200 cases of MERS-CoV reported in 2019.

Health authorities around the world continue to monitor MERS cases.

SARS-CoV-2

SARS-CoV-2 causes COVID-19. This new coronavirus appeared in Wuhan, China, in late December 2019 after health officials noticed an increase in pneumonia cases with no known cause.

These cases have since been linked to a market selling seafood and poultry. Though the virus likely evolved from an animal source, its exact source is unknown.

Within a few months, SARS-CoV-2 has spread to hundreds of countries around the world after being transmitted through person-to-person contact.

The virus that originated in China in 2019 is a new coronavirus that likely evolved from an animal source. It’s been named SARS-CoV-2.

SARS-CoV-2 causes the illness known as COVID-19. It’s dangerous because it’s transmitted easily from person-to-person, whether or not the person is exhibiting symptoms.

As the virus continues to spread around the world, many countries are asking people to stay home to prevent transmission.

There’s currently no known vaccine or medical treatment for COVID-19. Research in these areas is ongoing.

The primary symptoms of COVID-19 include:

Less common symptoms of COVID-19 include:

  • sore throat
  • nasal congestion
  • muscle aches and pains
  • diarrhea
  • loss of taste or smell
  • headache
  • chills, which may sometimes occur alongside repeated shaking

COVID-19 might feel different than symptoms of a cold, the flu, or allergies. In addition, not everyone with a SARS-CoV infection has symptoms.

Coronaviruses are zoonotic viruses. That means they commonly affect animals, such as:

  • birds
  • bats
  • camels
  • pigs

In rare cases, coronaviruses “jump” species, which means they’re transmitted from an animal with an infection to a human through direct or indirect contact. Scientists call this event a zoonotic spillover.

When this happens, the resulting coronavirus poses a threat to human populations, as is the case with SARS-CoV-2.

The CDC recommends that all people wear cloth face masks in public places where it’s difficult to maintain a 6-foot distance from others.
This will help slow the spread of the virus from people without symptoms or people who do not know they have contracted the virus.
Cloth face masks should be worn while continuing to practice physical distancing. Instructions for making masks at home can be found here.
Note: It’s critical to reserve surgical masks and N95 respirators for healthcare workers.

The following basic protective measures can help you protect yourself from COVID-19:

  • Stay home. According to the CDC, the best way to protect yourself from the virus is to avoid being exposed to it. That means staying home to avoid coming into contact with people who might have the virus.
  • Wash your hands often and thoroughly. Wash your hands with soap and water for at least 20 seconds, especially if you’ve been in a public area.
  • Use an alcohol-based hand sanitizer. When it’s not possible to wash your hands, use a hand sanitizer with at least 60 percent alcohol content.
  • Avoid touching your face. The virus can survive on surfaces that you touch with your hands. If your hands come into contact with your mouth, nose, and eyes, the virus might enter your body.
  • Practice social distancing. If you need to leave your house, maintain your distance from anyone who might have the virus, especially if the virus is being transmitted in your community. The CDC recommends staying at least 6 feet (1.83 meters) away from others.
  • Seek regular updates. The situation is evolving rapidly. It’s important to follow instructions from public health officials.

Coronaviruses are a family of viruses that cause cold- and flu-like symptoms in humans.

There are seven types of coronaviruses. Four common human coronaviruses are mild and pose less risk to people.

Three other human coronaviruses (SARS-CoV, MERS-CoV, and SARS-CoV-2) originated in animals and were transmitted to humans. They pose greater risks to people.