Severe acute respiratory syndrome (SARS) is caused by the SARS coronavirus, known as SARS CoV.

Coronaviruses are common viruses linked to infections in humans and animals.

There are several recognised human coronaviruses that cause mild respiratory infections, such as the common cold. However, this type of virus can also include strains that cause more severe illnesses, such as SARS.

There have been two self-limiting SARS outbreaks to date, during 2002 to 2004 (see below) associated with a highly contagious and potentially life-threatening form of pneumonia. Since 2004, there haven't been any known cases of SARS reported anywhere in the world.

Symptoms of SARS

SARS has flu-like symptoms that usually begin two to seven days after infection. In some cases, the incubation period (the time between exposure to the virus and the onset of symptoms) can be up to 10 days.

The symptoms of SARS include:

  • a high temperature (fever) over 38C (100.4F)
  • fatigue (extreme tiredness)
  • headaches 
  • chills
  • muscle pain
  • loss of appetite
  • diarrhoea

After these symptoms the infection will begin to affect your respiratory system (lungs and airways), leading to additional symptoms such as:

  • a dry cough
  • breathing difficulties
  • an increasing lack of oxygen in the blood, which can be fatal in the most severe cases

The SARS pandemic

SARS originated in China in 2002. The infection quickly spread to other countries (a pandemic), and resulted in more than 8,000 cases and 774 deaths before the virus was eventually brought under control.

It's thought a strain of the coronavirus usually only found in small mammals mutated (a DNA change occurred), enabling it to infect humans.

The SARS infection quickly spread from China to other Asian countries. There were also a small number of cases in several other countries, including four in the UK, plus a significant outbreak in Toronto, Canada.

The SARS pandemic was eventually brought under control in July 2003, following a policy of isolating people suspected of having the condition, and screening all passengers travelling by air from affected countries for signs of the infection.

During the period of infection, there were 8,098 reported cases of SARS and 774 deaths. This means that the virus killed about one in 10 people who were infected. People over 65 years of age were particularly at risk, with over half dying from the infection in this age group.

In 2004, there was another small SARS outbreak linked to a medical laboratory in China. It was thought to have been the result of someone coming into direct contact with a sample of the virus, rather than being caused by animal-to-human or human-to-human transmission.

How SARS is spread

SARS is an airborne virus, which means it's spread in a similar way to colds and flu.

The SARS virus is spread in small droplets of saliva coughed or sneezed into the air by an infected person. If someone else breathes in the droplets they can become infected.

SARS can also be spread indirectly if an infected person touches surfaces, such as door handles, with unwashed hands. Someone who touches the surface may also become infected.

The SARS virus may also be spread through an infected person’s faeces (stools). For example, if they don't wash their hands properly after going to the toilet, they may pass the infection on to others.

Evidence from the SARS pandemic in 2002/03 showed that people living with or caring for someone with a known SARS infection were most at risk of developing the infection themselves.

Treatment for SARS

There's currently no cure for SARS but research to find a vaccine is ongoing.

A person suspected of having SARS should be admitted to hospital immediately and kept in isolation under close observation.

Treatment is mainly supportive and may include:

  • assisting with breathing using a ventilator to deliver oxygen
  • antibiotics to treat bacteria that cause pneumonia
  • antiviral medications
  • high doses of steroids to reduce swelling in the lungs

There's little in the way of scientific evidence to show that these treatments are effective. The antiviral medication, ribavirin, is known to be ineffective at treating SARS.

Prevention advice

Avoid travelling to areas of the world where there's an uncontrolled SARS outbreak.

To reduce your risk of becoming infected, avoid direct contact with people with SARS (until at least 10 days after their symptoms have gone).

To avoid spreading the infection, it's important to follow the prevention advice outlined below:

  • wash your hands thoroughly using an alcohol-based hand detergent
  • cover your mouth and nose when you sneeze or cough
  • avoid sharing food, drink and utensils
  • regularly clean surfaces with disinfectant

In some situations, it may be appropriate to wear gloves, masks and goggles to help prevent the spread of SARS.

Future SARS outbreaks

Although the threat of SARS to public health seems to have passed, international health officials continue to remain vigilant.

The World Health Organization (WHO) monitors countries throughout the world for any unusual disease activity.

Therefore, if another SARS outbreak were to occur, it should be possible to limit the spread of infection using the same measures that were implemented during the 2002/03 pandemic (see above).

The SARS virus 

Viral mutations

Like all living things, viruses are constantly changing and evolving. A mutation is where genetic information stored inside an organism changes.

Mutations occur randomly and most aren't particularly significant. However, sometimes by chance, a mutated virus is able to infect humans.

Many pandemics (global outbreaks of infectious illnesses) that have occurred in recent history are thought to have been caused by viruses previously only found in animals. After mutating, the viruses became capable of infecting humans.

Examples of mutated viruses include:

  • SARS
  • HIV thought to be a mutated version of a virus found in monkeys
  • avian flu – a mutated version of a flu virus found in birds
  • swine flu a mutated version of a flu virus thought to have originated in pigs

Page last reviewed: 03/10/2014

Next review due: 03/10/2016