Severe acute respiratory syndrome (SARS) is the first emergent and highly transmissible viral disease to appear during the twenty-first century. SARS is a potentially life-threatening disease. It is caused by a virus of the Coronaviridae family. The Coronaviridae family of viruses is also responsible for many common colds. SARS, however, is far more serious than a cold.
Chinese health officials initially remained silent about the outbreak, and no special precautions were taken to limit travel or prevent the spread of the disease. The world health community, therefore, had no chance to institute testing, isolation, and quarantine measures that might have prevented the subsequent global spread of the disease.
On February 21, Jianlun Liu, a 64-year-old Chinese physician from Zhongshan hospital (later determined to have been a “super-spreader,”—a person capable of infecting unusually high numbers of contacts) traveled to Hong Kong to attend a family wedding despite the fact that he had a fever. Epidemiologists subsequently determined that, Liu passed on the SARS virus to other guests at the Metropole Hotel where he stayed, including an American businessman en route to Hanoi, three women from Singapore, two Canadians, and a Hong Kong resident. Liu's travel to Hong Kong and the subsequent travel of those he infected allowed SARS to spread from China to the infected travelers' destinations.
Johnny Chen, the American businessman, grew ill in Hanoi, Vietnam, and was admitted to a local hospital. Chen infected 20 health care workers at the hospital including noted Italian epidemiologist Carlo Urbani who worked at the Hanoi World Health Organization (WHO) office. Urbani provided medical care for Chen and first formally identified SARS as a unique disease on February 28, 2003. By early March, 22 hospital workers in Hanoi were ill with SARS.
Unaware of the problems in China, Urbani's report drew increased attention among epidemiologists when coupled with news reports in mid-March that Hong Kong health officials had also discovered an outbreak of an acute respiratory syndrome among health care workers. Unsuspecting hospital workers had admitted the Hong Kong man infected by Liu to a general ward at the Prince of Wales Hospital because it was assumed he had a typical severe pneumonia—a fairly routine admission. The first sign that clinicians were dealing with an unusual illness came from the observation that hospital staff, and those determined to have been in close proximity to the infected persons had become ill. There were still no health notices from China of increasing illnesses and deaths due to SARS.
After many of the Hong Kong hosptial staff became ill, Hong Kong authorities decided that those experiencing flu-like symptoms would be given the option of self-isolation, with family members allowed to remain confined at home or in special camps. Compliance checks were conducted by police.
One of the most intriguing aspects of the early Hong Kong cases was a cluster of more than 250 SARS cases that occurred in a group of high-rise apartment buildings—many housing health care workers—that provided evidence of a high rate of secondary transmission. Epidemiologists conducted extensive investigations to rule out the hypothesis that the illnesses were related to some form of local contamination (e.g., sewage, bacteria in the ventilation system). Rumors began that the illness was due to cockroaches or rodents, but no scientific evidence supported the hypothesis that the disease pathogen was carried by insects or animals.
One of the Canadians infected in Hong Kong, Sui-Chu Kwan, return to Toronto, Ontario, and died in a Toronto hospital on March 5. As in Hong Kong, because there was no alert from China about the SARS outbreak, Canadian officials did not initially suspect that Kwan had been infected with a highly contagious virus, until Kwan's son and five health care workers showed similar symptoms. By mid-April, Canada reported more than 130 SARS cases and 15 fatalities.
Faced with reports that provided evidence of global dissemination, on March 15, 2003, the World Health Organization (WHO) took the unusual step of issuing a travel warning that described SARS as a “worldwide health threat.” WHO officials announced that SARS cases, and potential cases, had been tracked from China to Singapore, Thailand, Vietnam, Indonesia, Philippines, and Canada. Although the exact cause of the “acute respiratory syndrome” had not, at that time, been determined, WHO officials issuance of the precautionary warning to travelers bound for Southeast Asia about the potential SARS risk served as notice to public health officials about the potential dangers of SARS.
WHO officials responded by recommending increased screening and quarantine measures that included mandatory screening of persons returning from visits to the most severely affected areas in China, Southeast Asia, and Hong Kong.
In early April 2003, WHO took the controversial additional step of recommending against non-essential travel to Hong Kong and Guangdong Province in China. The recommendation, sought by infectious disease specialists, was not controversial within the medical community, but caused immediate concern regarding the potentially widespread economic impacts.
Mounting reports of SARS showed an increasing global dissemination of the virus. By April 9, the first confirmed reports of SARS cases in Africa reached WHO headquarters, and eight days later, a confirmed case was discovered in India.
The outbreak of SARS lasted from November 2002 through July 2003. The last reported cases occurred in China in 2004. As of mid-2012, no additional cases of SARS have been reported anywhere in the world.
State governments within the United States have a general authority to set and enforce quarantine conditions for threats to public health. At the federal level, the Centers for Disease Control and Prevention (CDC) Division of Global Migration and Quarantine is empowered to detain, examine, or conditionally release (release with restrictions on movement or with a required treatment protocol) individuals suspected of carrying certain listed communicable diseases, including SARS.
During the 2002–2003 SARS outbreak, about 8,000 people were infected, including many health care workers, and 774 deaths were reported (9.6% of reported cases). The majority of cases occurred in mainland China, followed by Hong Kong, Taiwan, and Singapore. There were 251 cases and 43 deaths in Canada and none in the United States.
The initial symptoms of SARS are non-specific flu-like symptoms of fever, headache, malaise, dry cough. Infected patients then typically spike a fever of 100.4°F (38°C) or higher as they develop a deep cough, shortness of breath, and difficult or painful breathing. SARS often fulminates (reaches it maximum progression) in a severe pneumonia that can cause respiratory failure and death.
In mid-April 2003, Canadian scientists at the British Columbia Cancer Agency in Vancouver announced that they that sequenced the genome of the coronavirus most likely to be the cause of SARS. Within days, scientists at the Centers for Disease Control (CDC) in Atlanta, Georgia, offered a genomic map that confirmed more than 99% of the Canadian findings.
The genetic map was generated from studies of viruses isolated from SARS cases. The particular coronavirus mapped had a genomic sequence of 29,727 nucleotides—average for the family of coronavirus that typically contain between 29,000–31,000 nucleotides.
Proof that the coronavirus map was the specific virus responsible for SARS eventually came from animal testing. Rhesus monkeys were exposed to the virus via injection and inhalation and then monitored to determine whether SARS-like symptoms developed. Sick animals were examined for histological pathology (i.e., an examination of the tissue and cellular level for signs of illness) similar to findings in human patients. Other tests, including polymerase chain reaction (PCR) testing helped positively match the specific coronavirus present in the lung tissue, blood, and feces of infected animals to the exposure virus.
To be diagnosed with SARS the individual must have
Blood cultures, Gram stains, chest radiographs, and tests for other viral respiratory pathogens such as influenza A and B may be done to rule out other illnesses. If SARS is suspected, samples are forwarded to state/local public health departments and/or the CDC for coronavirus antibody testing.
As of mid-2012, no specific treatments or therapies had been developed to treat SARS. Antibiotics are ineffective against the SARS and all other viruses. Antiviral medications may be used, but their effectiveness remains unproven. Supportive therapy, such as the administration of fluids, oxygen, ventilation, and fever control are the only available treatments.
Based on a single past outbreak, about 10% of infected individuals would be expected to die from complications of SARS.
Isolation and quarantine remain the best tools to prevent the spread of SARS. Both procedures seek to control exposure to infected individuals or materials. Isolation procedures are used with patients with a confirmed illness. Quarantine rules and procedures apply to individuals who are not currently ill, but have been exposed to the illness (e.g., been in the company of an infected person or come in contact with infected materials).
Isolation and quarantine both act to restrict movement and to slow or stop the spread of disease within a community. Depending on the illness, patients placed in isolation may be cared for in hospitals, specialized health care facilities, or in less severe cases, at home. In some cases, isolation and quarantine are voluntary; however, isolation and quarantine can be compelled by federal, state, and some local law.
See also Communicable diseases ; Housing ; Rodents ; Sanitation ; Viruses .
Abraham, Thomas. Twenty-first Century Plague: The Story of SARS. Baltimore, MD: Johns Hopkins University Press, 2005.
Centers for Disease Control and Prevention (CDC). Severe Acute Respiratory Syndrome (SARS) February 12, 2012 [accessed June 26, 2012]. http://www.cdc.gov/sars/index.html
Severe Acute Respiratory Syndrome. MedlinePlus. February 29, 2012 [accessed June 26, 2012]. http://www.nlm.nih.gov/medlineplus/severeacuterespiratorysyndrome.html
Trivedi, Manish N. Severe Acute Respiratory Syndrome. Medscape.com [accessed June 26, 2012]. http://emedicine.medscape.com/article/237755-overview
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Brenda Wilmoth Lerner
Revised by Tish Davidson, AM