Coronaviruses cause a range of illnesses, including COVID-19. They typically affect the respiratory tract, but their effects can extend well beyond the respiratory system.

At the end of 2019, scientists identified a coronavirus outbreak in China. Experts named the newly identified virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the illness that it causes coronavirus disease 19 (COVID-19).

There are many types of coronavirus. Some cause mild illnesses, such as the common cold. Others can cause severe acute respiratory syndrome (SARS) or Middle East respiratory syndrome (MERS), which can be life threatening.

Many coronaviruses are present in animals but do not affect humans. Sometimes, however, a virus mutates in a way that allows it to infect humans. Scientists call these human coronaviruses, or “HCoVs.”

This article looks at a few coronaviruses that can infect humans, the illnesses they cause, and how they transmit. Specifically, we focus on three dangerous diseases caused by coronaviruses: COVID-19, SARS, and MERS.

Coronavirus resources

For more advice on COVID-19 prevention and treatment, visit our coronavirus hub.

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Researchers first identified a coronavirus in 1937. They isolated one that was responsible for a type of bronchitis in birds and had the potential to devastate poultry stocks.

Scientists found evidence of human coronaviruses in the 1960s, in the noses of people with the common cold. Several human coronaviruses cause mild illnesses, including colds.

The name “coronavirus” refers to the crown-like projections on the pathogen’s surface. “Corona” in Latin means “halo” or “crown.”

In humans, coronavirus infections most often occur in the winter and early spring, but they can happen at any time.

Learn more about how coronaviruses affect the body.

Late in 2019, scientists started monitoring the outbreak of a new coronavirus, SARS-CoV-2, which causes COVID-19. They first identified the virus in Wuhan, China.

The virus spread rapidly around the world, and the World Health Organization (WHO) declared a pandemic in March 2020.

The new coronavirus has been responsible for millions of infections globally, and it has caused more than 2 million deaths. The mortality rate varies from country to country. In the United States, it is around 1.7%.

Many researchers believe SARS-CoV-2 first infected bats before spreading to other animals, including humans. Some of the first people with COVID-19 had links to a live animal and seafood market. Overall, however, there is little conclusive information about the origins of the virus. Scientists are still investigating its source and initial pattern of spreading.

Many people with COVID-19 experience a relatively mild form of the disease that does not require specialist treatment. Others develop severe breathing problems and need to spend time in the hospital. In some cases, it is fatal.

Some people who do not have severe symptoms initially go on to develop health issues that continue for weeks or months, according to the Centers for Disease Control and Prevention (CDC).

People with a higher risk of severe COVID-19 symptoms include older adults and those with underlying medical conditions, including high blood pressure, heart and lung problems, diabetes, and cancer.

According to the CDC, most children with COVID-19 have mild or no symptoms. Fewer children have developed COVID-19 than adults. That said, infants and children with certain medical conditions may have an increased risk of severe illness and death.

There may also be a higher risk of severe COVID-19 during pregnancy, as well as an increased risk of issues such as preterm birth. However, the role of the virus in these circumstances remains unclear.

Which treatments can help with COVID-19?

Symptoms of COVID-19

People may start to experience COVID-19 symptoms 2–14 days after exposure to SARS-CoV-2.

Symptoms of COVID-19 include:

  • a fever
  • chills
  • a cough
  • shortness of breath or difficulty breathing
  • a sore throat
  • congestion or a runny nose
  • fatigue
  • a headache
  • muscle pain
  • a new loss of taste or smell
  • nausea, vomiting, or both
  • diarrhea

Tests can detect the infection, even if there are no symptoms.

As the virus progresses, severe complications can arise. COVID-19 can affect a wide range of body systems and lead to multiple organ failure.

Systemic inequalities in healthcare have increased the risk of illness and death for people in marginalized racial and ethnic groups. Read more here.

SARS is a disease caused by an infection with a different coronavirus — SARS-CoV. It can lead to a life threatening form of pneumonia.

SARS first appeared in Asia in February 2003. The virus then spread to more than two dozen countries, resulting in 8,098 infections and 774 deaths. The last reported cases in humans occurred in a laboratory-related outbreak in China in 2004.

Symptoms of SARS

Early symptoms are flu-like and include:

  • a high fever
  • a headache
  • body aches
  • a feeling of discomfort
  • mild respiratory symptoms, in some cases

The infection affects both the upper and lower respiratory tracts. After 7–10 days, the person may develop a dry cough. Also, pneumonia, a severe lung infection, often develops.

As SARS progresses, it can lead to failure of the lungs, liver, or heart.

During the outbreak, complications were more common among older adults. According to one source, more than half of those who died from the disease were over the age of 65.

MERS is a severe respiratory illness caused by the MERS-CoV coronavirus. Scientists first recognized it in 2012 after reports in Saudi Arabia. After that, it spread to other countries, including the U.S.

MERS has not become widespread in the same way as COVID-19. According to reported figures, about 30–40% of people with MERS die from the disease.

Symptoms of MERS

These symptoms include:

  • a fever
  • breathlessness
  • coughing
  • nausea, diarrhea, and vomiting, in some cases

Complications include pneumonia and kidney failure.

The illness spreads through close contact with people who have the infection.

People aged 1–99 years have had MERS, and severe symptoms were more common among older people and those with underlying health conditions or weakened immune systems.

Coronavirus infections are contagious, and some of these viruses, including the one that causes COVID-19, spread easily between people. Researchers believe that the viruses transmit via fluids from the respiratory system.

Transmission may happen when a person:

  • coughs or sneezes without covering their mouth, dispersing droplets containing the virus into the air
  • has physical contact with someone who has the infection
  • touches a surface that contains the virus, then touches their nose, eyes, or mouth

Ways of preventing transmission include:

  • wearing a face covering in public
  • avoiding touching the face, especially the mouth and nose
  • always coughing or sneezing into a tissue, then disposing of it and washing the hands right away
  • regularly and thoroughly washing the hands

During the ongoing COVID-19 pandemic, people should also do the following, even if they are well:

  • Stay home whenever possible.
  • Avoid contact with others.
  • Wear a face covering in public.
  • Stay at least 6 feet away from others in public.

Anyone with symptoms of COVID-19 should isolate at home and rest until the symptoms have passed. Contact a doctor for more information, and let them know if the symptoms seem to be worsening.

Vaccines can help prevent infection with SARS-CoV-2. Learn more here.

Coronaviruses are present in humans and other animals, and some types can cause severe illness.

The common cold is one illness that can result from a coronavirus. Others include SARS, MERS, and COVID-19.

Scientists continue to investigate coronaviruses and monitor for new types and outbreaks.

Keep up to date about the current COVID-19 outbreak. The CDC also have a resource describing ways to reduce the risk of infection.

Read the article in Spanish.