Severe acute respiratory syndrome, or SARS, is a contagious and potentially fatal respiratory illness.

It first appeared in China in November 2002 and was identified in February 2003.

SARS spread to over 24 countries before it was contained. Since May 2004, no new cases have been reported.

From November 2002 to July 2003, there were 8,098 cases worldwide and 774 deaths.

The United States (U.S.) saw eight laboratory-confirmed cases and no fatalities. All eight people had traveled to areas affected by SARS.

Strong levels of global cooperation ensured that the threat of SARS was dealt with swiftly, and the spread of the disease was effectively contained.

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SARS is extremely contagious, and many wore face masks during the last outbreak in 2002.

The SARS coronavirus (SARS-CoV) causes SARS. A coronavirus is a common form of virus that typically causes upper-respiratory tract illnesses. The common cold results from a kind of coronavirus.

Six different kinds of coronavirus are known to infect humans. Four of these are common, and most people will experience at least one of them at some time in their life.

The two other types cause SARS and Middle East Respiratory Syndrome (MERS). These are less common but far more deadly.

Before SARS appeared, coronaviruses had not been particularly dangerous to humans, but they had been known to cause severe diseases in animals.

As a result, scientists first thought that animals transmitted SARS-CoV to humans. They now believe that an animal virus changed into a new, more deadly strain.

Droplets from coughing and sneezing and close human contact likely transmit the SARS virus. The respiratory droplets are probably absorbed into the body through the mucous membranes of the mouth, nose, and eyes.

This could be through:

  • hugging and kissing
  • sharing utensils for eating and drinking
  • speaking to someone within a distance of 3 feet
  • touching someone directly

A person with the virus can spread the infection by leaving respiratory droplets on objects, such as door handles, doorbells, and telephones. These are then picked up by someone else.

The virus is likely to remain active in the environment for several days.

Why do we worry about zoonotic diseases?

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SARS was the first coronavirus to present severe symptoms in humans.

Diseases that pass from animals to humans are called zoonotic diseases. They are relatively rare.

The main concern when they first emerge is that they are new strains and also new to humans, so the human body does not yet have immunity.

It is often impossible to predict what may happen. In the case of SARS, animals may have been a host for the virus.

In 2013, scientists discovered that two new coronaviruses found in Chinese horseshoe bats are a close relative of the SARS-coronavirus.

A report published in 2014 suggested that over 320,000 mammal viruses have not yet been discovered.

Symptoms normally appear within 3 to 5 days after exposure to the SARS virus, but they can develop after 2 to 7 days. During the incubation period, before symptoms appear, the disease is not contagious.

Most cases of SARS begin with a high fever. Other early symptoms include those common to flu, such as aches, chills, diarrhea, dry coughing, and shortness of breath. These will develop over the course of a week.

Patients may go on to develop pneumonia, an infection of the lungs.

Serious complications, such as respiratory failure, heart failure, and liver failure may occur.

These complications are more likely in people aged over 60 years, and those with pre-existing co-morbidities, such as diabetes or hepatitis.

The World Health Organization (WHO) advises that, to be diagnosed with SARS, a person must have all of the following:

  • a fever of at least 100.4° Fahrenheit or 38° Celsius
  • one or more symptoms of lower respiratory tract illness: a cough, difficulty breathing, shortness of breath
  • radiographic evidence to suggest a diagnosis of pneumonia
  • no alternative diagnosis to fully explain the illness

SARS is very rare, and the symptoms overlap with those of flu and pneumonia. A physician will not suspect it unless the person has been in an area where there is an outbreak.


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Tests can help confirm a diagnosis of SARS by detecting the virus and antibodies.

Laboratory tests can help identify SARS-CoV.

Reverse transcription-polymerase chain reaction (RT-PCR) testing can detect the virus in blood, stool, and nasal secretions.

Serologic testing can detect SARS-CoV antibodies in the blood. If a person has antibodies, they are also likely to have the infection.

Doctors may also use a viral culture. This involves putting a small same of body tissue or fluid into a container with some cells in which the virus can grow. If the virus grows, the cells will change.

These tests may not be reliable if used in the early stages of infection.

Most of the patients who developed SARS in 2003 to 2004 had spent time with people who developed the disease, or they had been in places where the disease was present.

Pneumonia is a common complication, so a person who develops unexplained pneumonia and has a spent time in a place where there is an outbreak should be suspected of having SARS.

This can include living in or recent travel to an area affected by SARS or working in a laboratory that contains live SARS-CoV.

The U.S. did not require people with SARS to enter quarantine during the 2003 outbreak, but SARS is a reportable disease. It is also a medical emergency, and urgent medical care is needed.

The WHO recommends isolating patients and using barrier techniques to prevent the spread of the virus, including filter masks and goggles. No drug, including antibiotics, appears to be effective against SARS.

Supportive care is recommended, including the use of medications to relieve symptoms such as fever and a cough.


As with other infectious diseases, some simple steps can be taken to help prevent the SARS virus from spreading.

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Effective personal hygiene can help to stop the spread of SARS.

Good personal hygiene practices can help restrict the spread of the virus.

These include:

  • frequent handwashing
  • avoiding touching the eyes, mouth or nose with unclean hands
  • covering the mouth and nose with a tissue when coughing or sneezing
  • encouraging others to do the same

Because SARS is contagious once its symptoms have developed, anyone with the disease should limit their interactions with other people until 10 days after their symptoms have improved. SARS is at its most contagious during the second week of illness.

Is there a vaccine?

There is currently no vaccine against SARS, but scientists are working on one.

In 2013, researchers announced that they had found a way to disable a part of the virus involved in SARS that allows it to hide from the immune system. This could lead to the development of a vaccine against the disease.

Since 2004, there have been no recorded cases of SARS anywhere in the world. Health organizations continue to work on a response, in case SARS reappears in the future.