Coronaviruses can cause a wide range of illnesses, including the common cold and COVID-19. These typically affect the respiratory system, but they can affect other systems, too.

Coronaviruses are present in many species, including camels and bats. Some of these viruses can infect humans, and some of the illnesses that they cause can be deadly.

A person might have a higher risk of developing severe symptoms if they are older, have a weakened immune system, or have another health condition.

In humans, coronaviruses can cause the common cold, severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS).

A coronavirus also causes coronavirus disease 19 (COVID-19). This illness results from an infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus is responsible for an ongoing pandemic and more than 2 million deaths so far.

Below, we explore how coronaviruses affect the body and take a close look at specific illnesses, including COVID-19.

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

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Viruses work by hijacking cells. They enter host cells and reproduce, then spread to new cells throughout the body.

As pathogens that the body does not recognize, viruses trigger an immune response. This can cause inflammation and other effects.

Coronaviruses are large, single-stranded RNA viruses with crown-like protein spikes on their surfaces. These spikes help them attach to and enter cells.

Coronaviruses spread among people through droplets from coughs, sneezes, or breathing. The droplets may land on another person on an item such as a door handle. If someone else touches the handle, the virus may pass on to them if they touch their mouth, nose, or eyes.

Once inside the body, coronaviruses mostly affect the respiratory system, including the nose and lungs. However, some viruses and the immune reaction they trigger can have a wider impact.

Where did COVID-19 come from, and how does it spread?

After exposure to SARS-CoV-2, a person is at risk of developing COVID-19. Someone with the infection may or may not have symptoms.

Like other coronaviruses, SARS-CoV-2 appears to pass from person to person through respiratory droplets. Once inside the body, it primarily affects the lungs.

In 2–14 days, the following symptoms may develop:

  • a persistent cough
  • shortness of breath
  • pain and tightening in the chest
  • a fever
  • fatigue
  • a loss of the senses of taste and smell

Around 80% of people with COVID-19 recover without needing specialist treatment, often in about 2 weeks. These people may experience mild flu-like symptoms.

But in others, COVID-19 has a severe impact on the lungs, leading to:

  • difficulty breathing
  • low levels of oxygen in the blood
  • lung injuries
  • pneumonia
  • pulmonary edema

Experts do not yet know precisely how the virus affects cells in the lungs. However, it seems clear that the body’s immune reaction, the impact of the virus on cells, and the lack of oxygen can each have life threatening consequences.

People who require hospital care often need help breathing, which may involve intubation and mechanical ventilation. This, too, can increase the risk of lung injuries.

In addition, having COVID-19 can increase the risk of damage to the:

  • blood
  • kidneys
  • nervous system and brain
  • cardiovascular system
  • gastrointestinal system

Some people have mild symptoms initially but go on to experience health problems for weeks or months.

Persistent symptoms can include:

  • fatigue
  • shortness of breath
  • a cough
  • joint pain
  • chest pain
  • a headache
  • muscle pain
  • a fever that comes and goes

COVID-19 can also cause:

In addition, there may be a risk of hormonal, dermatological, and musculoskeletal complications, although there is not enough evidence yet to confirm this.

Is it COVID-19, a cold, or the flu? Here, learn to tell the difference.

More than 200 viruses can cause a cold, including some coronaviruses.

The symptoms mainly involve the upper respiratory tract and can include:

The symptoms of a cold are not usually severe and tend to pass in about 7 days. However, they can linger for weeks. Also, complications can arise, such as:

People with asthma, emphysema, and chronic bronchitis may have a higher risk of symptoms and complications.

Anyone with cold symptoms that are persistent or occur with a fever, ear pain, or sinus pain should receive medical attention.

What are the stages of a cold?

A coronavirus also causes SARS, a serious illness that emerged in China in 2003 and spread to more than 30 countries before being contained.

Symptoms of SARS include:

It primarily affects the respiratory system and can injure the lungs. Experts believe that this results from the immune response that the virus triggers.

The symptoms usually appear after 5–7 days, and 95% of people who develop SARS symptoms do so by day 10. Around 30% feel better after a week.

In severe cases, the symptoms often worsen toward the end of the second week. If this happens, the person may develop any of the following complications:

SARS caused 774 deaths. Approximately half of these were people older than 60, and 21% of the total were healthcare workers. The fatality rate was more than 9.6%.

Experts believe that the SARS virus passed from a horseshoe bat to a palm civet and then to humans.

How do SARS and MERS compare with COVID-19?

MERS appeared in 2012 in Saudi Arabia and caused severe respiratory symptoms. It was fatal in around 30–40% of cases, mostly among people with an underlying illness or weakened immune system.

Symptoms usually appeared 5–6 days after exposure but this could range from 2–14 days.

A person with MERS may have:

A person may have mild or no symptoms, or symptoms resembling a cold. Some people initially experienced mild symptoms, then developed pneumonia.

Beyond the respiratory effects, MERS can also affect the gastrointestinal and neuromuscular systems. And as with other illnesses caused by coronaviruses, the symptoms of MERS can result from the virus itself and the immune response to it.

Most people with MERS had contact with camels.

There is currently no cure for any viral infection. The best treatment for the illnesses above depends on the type of coronavirus responsible, the specific symptoms and their severity, and the drugs available.

Viruses do not respond to antibiotics. Doctors recommend managing the symptoms of these infections at home, if possible, using over-the-counter pain relief and cough medications.

They may also recommend antiviral or other medications to slow the progression of the disease and reduce the risk of severe symptoms.

Anyone with complications or severe symptoms may need care in a hospital, including:

  • oxygen therapy and breathing assistance
  • drugs to reduce inflammation, such as corticosteroids
  • other therapies to manage complications such as secondary infections

Vaccines are now becoming available to help reduce the risk of developing COVID-19.

Learn more about treatments for COVID-19.

Coronaviruses are responsible for several illnesses, ranging from the common cold to COVID-19.

These viruses usually cause respiratory symptoms, such as a cough, and signs of an infection, such as a fever and fatigue. However, they can also affect many of the body’s systems. In some cases, they cause fatal illness.

Experts are still investigating how coronaviruses affect the body and the best ways to combat them.