I.

Introduction

Severe Acute Respiratory Syndrome (SARS), contagious respiratory illness that can cause a fatal form of pneumonia. The illness first appeared in November 2002 in people living in Guangdong province in southern China. Its cause was unknown and available treatments were ineffective. By February 2003 new cases of the illness were reported in Hong Kong, Vietnam, Singapore, and Canada. The fast spread of the disease, its deadly nature, and its unknown cause prompted the World Health Organization (WHO), an agency of the United Nations, to issue a global alert in March 2003 designating SARS as a worldwide health threat. The alert triggered governments around the world to establish infection-control procedures to prevent the illness from reaching epidemic proportions. Despite these public-health measures, more than 8,000 SARS cases were reported in 32 countries and the disease caused 800 deaths by the time the outbreak was declared contained in July 2003.

II.

Symptoms and Treatment

SARS symptoms begin with a fever about 38°C (about 100.4°F) or higher, chills, headache, and malaise. Two to seven days later some people develop a dry cough and difficulty breathing. Symptoms may progress to a severe form of pneumonia, in which air sacs in the lungs fill with fluid, preventing oxygen from reaching blood cells and nourishing the other cells of the body. Aside from regular nursing care and the use of a respirator to help breathing in severe cases, there is no effective treatment for SARS. Recovery seems to depend on the health of the patient’s immune system. Epidemiologists (scientists that study the cause and spread of diseases) have found that those most susceptible to the fatal form of the illness are aged 40 or older and have a history of a chronic disease.

III.

How the Illness Spreads

Infection with SARS results from close contact with an infected person. SARS can spread if a person inhales droplets sprayed into the air when an infected person coughs or sneezes. SARS may also spread when a person touches an object that has been contaminated. Scientists are investigating if the infection can spread in other ways. Symptoms typically develop two to seven days after exposure, so someone may unknowingly become infected and spread the illness before developing symptoms. In Asia, before infection-control measures were established, many SARS cases occurred among hospital workers who cared for SARS patients. These infected hospital workers, in turn, spread the illness to people living in their households. Most SARS cases reported in Canada were in people who became infected with the illness while traveling abroad or people who were exposed to infected travelers from abroad.

IV.

Cause

Although studies are incomplete, scientists suspect that a newly discovered virus from the coronavirus family causes SARS. Until now coronaviruses have been known to cause only minor illnesses in humans, such as colds or diarrhea. Scientists theorize that the SARS virus may have passed to humans from an animal. The virus then underwent a series of genetic mutations (changes) to acquire properties that cause severe illness in humans.

Researchers have developed laboratory tests that identify the SARS virus in infected people. These tests can help epidemiologists determine how long someone infected with SARS remains contagious and if those infected develop long-term immunity to the disease.

V.

Prevention

Researchers in Hong Kong have identified chemicals that may prevent the virus from replicating once it infects a human body. Other researchers are investigating if genetically engineered antibodies are effective in blocking the virus. In addition, efforts to develop a vaccine that would prevent SARS are underway.

Until effective treatments can be developed, public-health officials have established infection-control measures to contain the spread of SARS. Those people diagnosed with SARS or suspected of having the illness are treated in isolation in their homes, in hospitals, or in other designated health-care settings. Caregivers follow strict procedures to lessen their own risk of infection. The WHO also issues travel advisories recommending against nonessential travel to certain countries where the risk of infection is high.