Severe Acute Respiratory Syndrome (SARS)

Severe acute respiratory * syndrome * (SARS) is a highly contagious * , potentially life-threatening respiratory illness caused by a coronavirus. Coronaviruses are members of a family of viruses that includes the causative agents of numerous animal and human diseases, including SARS and the common cold.

What Is Severe Acute Respiratory Syndrome?

* . Although SARS subsequently disappeared, it left a legacy of fear and severe economic consequences.

Coronaviruses are a group of viruses * so named because they appear to be surrounded by a halo or corona when viewed under an electron microscope. They are large viruses carrying single-stranded RNA * as their genetic * material. In animals, coronaviruses can cause serious respiratory, gastrointestinal * , liver, and neurological * disease. In humans, however, coronaviruses normally cause only mild-to-moderate upper respiratory tract infections like the common cold. Because of this previous pattern, health officials were taken by surprise when the death toll from the first wave of SARS approached 15 percent and exceeded 50 percent in patients over age 65. Respiratory failure * is the most common cause of death from SARS, with heart failure or liver failure as other potential complications.

How Common Is Severe Acute Respiratory Syndrome?

According to the World Health Organization (WHO), 8,098 people became ill with SARS during the 2003 outbreak and 774 of them died. Scientists believe that some of the cases originally diagnosed as SARS may actually have been avian influenza * , or bird flu, a potentially far more deadly disease. Most of the early victims were healthcare workers or family members of SARS patients.


Within weeks of the first recognized SARS cases, scientists had identified a coronavirus as the causative agent and immediately suspected that it was an animal virus that had crossed over to infect humans. Palm civets— small Asian weasel-like mammals—were the suspected culprit. Civets are considered a delicacy in southern China and are commonly sold in livefood markets and restaurants. Early SARS victims included a waitress at a restaurant in Guangzhou, China, that served palm civet, and a customer seated close to the restaurant's animal cages. SARS-CoV was subsequently found in other animals, including domestic cats, and bats were identified as a natural reservoir for SARS-like coronaviruses. Researchers eventually came to believe that the epidemic * SARS strain evolved through a series of transmissions between bats and livestock in southern China, followed by interactions between humans and palm civets in Guangzhou markets.

Illustration of the SARS virus. The membrane and protein envelope (violet) surround a genome of single-stranded RNA. The entire virus is surrounded by glycoproteins (orange) that suggest a corona or crown.

Illustration of the SARS virus. The membrane and protein envelope (violet) surround a genome of single-stranded RNA. The entire virus is surrounded by glycoproteins (orange) that suggest a corona or crown.
Jim Dowáalls/Science Source.

How Is Severe Acute Respiratory Syndrome Spread?


In November 2002 a farmer in the Pearl Delta region of Guangdong province in southeastern China died of an undiagnosed illness. On November 27, 2002, Canada's Global Public Health Intelligence Network picked up Internet reports of a flu outbreak in China and forwarded the reports to the World Health Organization (WHO). However, the Chinese government restricted media coverage and did not inform WHO of the outbreak until February 2003.

On February 21, 2003, a Chinese doctor who had been treating patients in a Guangdong hospital checked into the Metropole Hotel in Hong Kong. On February 26, Johnny Chen, an American businessman living in Shanghai, stayed at the Metropole before catching a flight to Singapore. When he became ill on the airplane, the flight was diverted to Hanoi, Vietnam. There, Carlo Urbani, an Italian WHO physician, identified Cheńs illness as a new disease. Chen died of SARS after transmitting the virus to hospital workers in Hanoi. Urbani died of SARS on March 29 at the age of 46. About 80 percent of SARS cases in Hong Kong were eventually traced back to the Chinese doctor. Within a few weeks travelers who had stayed at the Metropole in February unwittingly spread the virus to Singapore, Taiwan, Europe, Africa, and North and South America.

Outside Asia, the city most affected by SARS was Toronto, Canada. A Canadian woman died of SARS shortly after returning to Toronto from Hong Kong. Her son entered a Toronto hospital with an illness that was later identified as SARS. While waiting 16 hours in the crowded emergency room, he infected two other people. WHO advised travelers to avoid Toronto, but on May 17, 2003, the outbreak was declared over. Then on May 23 a second larger SARS outbreak was traced to another hospital. Healthcare workers accounted for 45 percent of the 251 SARS cases eventually diagnosed in the province.

As is the case with most other respiratory infections, SARS is spread primarily by close person-to-person contact through the droplets produced when an infected person talks, coughs, or sneezes. Droplets can be propelled up to about three feet, encountering the mucous membranes *

SARS is thought to be contagious only while symptoms of the illness are present. It is most contagious during the second week of illness. Susceptibility * to SARS increases with age. Children are least likely to become ill.

Scientists have identified a variation in an immune system * gene * that may make people much more susceptible to SARS. This variation is common in people of Southeast Asian descent but is rare in other populations.

How Do People Know They Have Severe Acute Respiratory Syndrome?

SARS causes flulike symptoms, usually within two to seven days of becoming infected, but it can take up to 10 days for symptoms to appear. The first symptom is usually a fever of at least 100.4°F (38.0°C). Headache, muscle pain, body aches, and chills sometimes appear 12 to 24 hours before the fever.

Other initial symptoms may include:

Most people with SARS develop pneumonia * . This condition may be accompanied by hypoxia * , in which oxygen levels in the blood are low, leading to shortness of breath.


On March 12, 2003, WHO issued a global SARS alert, followed by travel advisories. Fearing a pandemic, WHO tracked and reported the disease daily until June 7, 2003. Schools were closed throughout Hong Kong and Singapore, and national economies were disrupted. International cooperation and quarantine * resulted in rapid containment of the virus.

Even so, China was sharply criticized for its initial response to SARS. In a letter circulated in the international news media, Jiang Yanyong, a surgeon in China's People's Liberation Army, reported that at least 100 people were being treated for SARS in Beijing hospitals. At that time Chinese authorities asserted that there were only a handful of cases in all of China. China's leaders were forced to admit that they had given WHO false information. Jiang was hailed as a hero both in China and abroad.

How Do Doctors Diagnose and Treat Severe Acute Respiratory Syndrome?


The symptoms of SARS are very similar to those of such other acute * severe respiratory infections as influenza. SARS is suspected only in a patient with a fever who has recently traveled to a region where SARS has been reported or who has been in close contact with someone with SARS. A probable SARS case is one that meets the above criteria (standards), along with chest x-rays or computed tomography * (CT) scans indicating atypical pneumonia or acute respiratory distress syndrome. Tests may be performed to rule out infection with other respiratory viruses or bacteria * that can cause pneumonia.

There are three laboratory tests that can confirm SARS:

Other diagnostic tests may include:


SARS requires immediate medical attention and hospitalization under isolation. There is no specific treatment for SARS as of 2016. SARS is managed similarly to other community-acquired atypical pneumonias, with intensive supportive medical care. About 10 to 20 percent of SARS patients require additional oxygen or mechanical ventilation due to breathing difficulties. Clinical studies have suggested that a combination of antiretroviral drugs used to treat AIDS * may prevent the most serious complications of SARS.

Can Severe Acute Respiratory Syndrome Be Prevented?

As with other infectious diseases, the best way to prevent SARS is frequent and effective hand washing with soap and water or use of a hand rub containing at least 60 percent alcohol. Unwashed hands should never touch the eyes, nose, or mouth.

The Centers for Disease Control and Prevention (CDC) recommends that people traveling to parts of the world where SARS has been reported take the following precautions:

The CDC recommends that a person suspected of having SARS should take the following precautions for 10 days after the fever and respiratory symptoms disappear:

See also Global Health Issues: Overview • Infection • Influenza • Pneumonia • Travel-related Infections: Overview • Viral Infections • Zoonoses: Overview


Books and Articles

Calisher, Charles H. Lifting the Impenetrable Veil: From Yellow Fever to Ebola Hemorrhagic Fever & SARS. Red Feather Lakes, CO: Gail Blindeess, 2013.

Willett, Edward. Infectious Disease Specialists: Hunting Down Disease. New York: Enslow Publishing, 2016.


Centers for Disease Control and Prevention. “Severe Acute Respiratory Syndrome (SARS).” (accessed July 7, 2016).

World Health Organization. “Severe Acute Respiratory Syndrome (SARS).” (accessed July 7, 2016).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA, 30329-4027. Toll-free: 800-232-4636. Website: (accessed July 7, 2016).

World Health Organization. Avenue Appia 20, 1211 Geneva 27, Switzerland. Telephone: 41 22 791 2111. (accessed July 7, 2016).

* respiratory (RES-pi-ra-tor-ee) refers to the breathing passages and lungs.

* syndrome is a group or pattern of symptoms or signs that occur together.

* contagious (kon-TAY-jus) means transmissible from one person to another, usually referring to an infection.

* pandemic (pan-DEH-mik) is a worldwide outbreak of disease, especially infectious disease, in which the number of cases suddenly becomes far greater than usual.

* viruses (VY-rus-sez) are tiny infectious agents that can cause infectious diseases. A virus can reproduce only within the cells it infects.

* RNA, or ribonucleic acid (RY-bonyoo-KLAY-ik AH-sid), is the chemical substance through which DNA sends genetic information to build new cells.

* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.

* gastrointestinal (GAS-tro-in-TEStih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the mouth, esophagus, stomach, intestines, colon, rectum, and other organs involved in digestion, including the liver and pancreas.

* neurological (nur-a-LAH-je-kal) refers to the nervous system, which includes the brain, spinal cord, and the nerves that control the senses, movement, and organ functions throughout the body.

* respiratory failure is a condition in which breathing and oxygen delivery to the body are dangerously altered.

* influenza (in-floo-EN-zuh), also known as the flu, is a contagious viral infection that attacks the respiratory tract, including the nose, throat, and lungs.

* epidemic (eh-pih-DEH-mik) is an outbreak of disease, especially infectious disease, in which the number of cases suddenly becomes far greater than usual. Usually epidemics are outbreaks of diseases in specific regions, whereas widespread epidemics are called pandemics.

* mucous membranes (MUkus) are the moist linings of the mouth, nose, eyes, and throat, as well as the respiratory, intestinal, and genital tracts.

* susceptibility (su-sep-ti-BIL-i-tee) means having less resistance to and higher risk of infection or disease.

* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.

* genes (JEENS) chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics such as hair or eye color. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.

* diarrhea (di-ah-RE-a) refers to frequent watery stools (bowel movements).

* nausea (NAW-zha) refers to a feeling of being sick to one's stomach or needing to vomit.

* pneumonia (nu-MO-nyah) is inflammation of the lungs.

* hypoxia (hip-AK-see-ah) is a condition that occurs when insufficient oxygen reaches the tissues of the body.

* quarantine is the enforced isolation (for a fixed period) of apparently healthy people or animals who may have been exposed to infectious disease.

* acute describes an infection or other illness that comes on suddenly and usually does not last very long.

* computed tomography (kom-PYOO-ted toe-MAH-gruhfee), or CT, formerly called computed axial tomography (CAT), is a technique in which a machine takes many x-rays of the body to create a three-dimensional picture.

* bacteria (bak-TEER-ee-a) are single-celled microorganisms, which typically reproduce by cell division. Some but not all types of bacteria can cause disease in humans.

* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

* culture (KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms.

* clotting is a process in which blood changes into a jellylike mass that stops the flow of blood.

* platelets (PLATE-lets) are tiny disk-shaped particles within the blood that play an important role in clotting.

* AIDS, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome, is an infection that severely weakens the immune system. It is caused by the human immunodeficiency virus (HIV).

  This information is not a tool for self-diagnosis or a substitute for professional care.