Infection: Severe Acute Respiratory Syndrome
Infection: Severe Acute Respiratory Syndrome
Severe acute respiratory syndrome, or SARS, is a potentially life-threatening infection of the upper respiratory tract caused by a new type
of virus that had not been seen before the fall of 2002. This new virus, which has been named the SARS-associated coronavirus (SARS-CoV), belongs to a family of viruses called coronaviruses because they have a crown-shaped appearance under a microscope. Before the SARS outbreak of 2002–2003, coronaviruses were thought of largely as a cause of the common cold. The SARS virus was identified as the cause of the disease by a researcher at the University of Hong Kong in March 2003.
SARS is defined by both WHO and the CDC as an emerging disease. This classification means that SARS is considered to be a disease that has become more widespread around the world in the last twenty years and may become more common in the future.
The first descriptions of SARS indicated that most patients thought at first that they had influenza. The early symptoms of the disease often include such flu-like symptoms as chills, sore muscles, fever, and a generally unwell feeling. In the second phase of the illness, the person develops a dry cough that can develop into pneumonia and difficulty breathing. At that point the person may need mechanical ventilation on a respirator.
SARS does not appear to strike any specific age group more frequently than any other. However, the elderly are at greatest risk of death from the disease. As far as is known, men and women are equally affected, as are people of all races and ethnic groups.
The country most severely affected by the 2002–2003 SARS epidemic was mainland China, with 5,327 confirmed cases and 349 deaths. In Hong Kong there were 1,755 cases and 299 deaths. The outbreak around Toronto, Canada, which involved 251 cases and forty-three deaths received considerable media attention and prompted widespread fear of the disease across North America. As of July 1, 2007, the CDC reported that there have been eight confirmed cases of SARS in the United States; all the patients had been traveling in countries where SARS had been reported. All eight patients survived.
One of the strange aspects of the SARS epidemic is that the disease has virtually disappeared since late 2004. The CDC reported on May 3, 2005, that “there is no known SARS transmission anywhere in the world” as of that date. The last known cases of SARS were reported in a group of Chinese
laboratory workers in April 2004. The WHO SARS Web site has not been updated since October 2004.
SARS is caused by a coronavirus belonging to the same family of viruses responsible for some common colds. The first known case of SARS occurred in a farmer in Guangdong Province, China, in November 2002. The farmer died shortly after being taken to the hospital. After the SARS virus was found in civets (small animals resembling otters or skunks) and other animals sold for food in the markets around Guangdong in May 2003, some researchers concluded that SARS is a zoonosis, or disease that people can get from animals. Almost all reported cases, however, involve person-to-person transmission through droplets released into the air when an infected person coughs or sneezes, or by direct contact with a drinking glass or other object touched by an infected person. The SARS virus also appears to remain in the air as small particles for some time after an infected person has sneezed. This method of transmission means that someone can get SARS even when he or she is not face to face with someone who has the disease.
SARS has an incubation period that can vary from two to ten days. The patient then runs a fever of around 100.4°F (38°C) or higher and experiences muscle aches, headache, and other influenza-like symptoms. About 20 percent of patients develop nausea and vomiting; some develop diarrhea as well.
The second phase of SARS begins about three days after the person first feels sick. The person develops a dry cough, has difficulty breathing, may wheeze, and begins to suffer from lack of oxygen in the blood. Even if the patient is helped by being placed on a respirator, he or she may die.
The diagnosis of SARS is usually based on a combination of the patient'shis-tory—particularly travel within the previous ten days to a country with reported cases of SARS—and the fever. Chest x rays do not always show anything unusual during the first week of infection, and the doctor may not hear anything abnormal when he or she listens to the patient's breathing.
A Medical Pioneer's Courage
Dr. Carlo Urbani (1956–2003) was a specialist in infectious diseases who worked for the World Health Organization (WHO). When the Vietnam French Hospital in Hanoi contacted WHO on February 28, 2003, about a patient who was seriously ill with an unidentifiable influenza-like virus, Urbani went immediately to Hanoi. Looking back, doctors now know that the hospital was trying to cope with an outbreak of SARS. Of the first sixty patients who had the new disease, more than half were doctors and nurses. In addition to carrying out the measures that were needed to control infection inside the hospital and sending samples for laboratory testing, Urbani recognized the seriousness of the situation and notified the Vietnamese government of the need for urgent public health measures. The government of Vietnam took the unusual step of calling for outside assistance rather than giving priority to its public image, as had happened in China.
Urbani flew to Bangkok, Thailand, on March 11 to meet an American doctor from the Centers for Disease Control and Prevention (CDC). During the flight he began to feel sick. Urbani was placed in an isolation room in a Bangkok hospital but died of SARS on March 29. He was only forty-six years old.
The Italian chapter of Doctors Without Borders, which had elected Urbani to be its president in 1999, credits him with saving the lives of thousands of people around the world by his timely and courageous warning to WHO and other public health organizations about the new disease.
When SARS first emerged, doctors had to make the diagnosis on the basis of the fever and the patient's history of travel or of close contact with an infected person. After the genome of the SARS virus was successfully sequenced (analyzed) by Canadian scientists in April 2003, it was possible to develop laboratory tests to detect antibodies to the virus and also take the first steps toward developing a vaccine. As of 2008, there were three types of diagnostic tests that can be used to detect SARS:
- A DNA rapid polymerase chain reaction test that uses a sample of blood or nasal secretions to check for the DNA of the SARS virus.
- A blood test that checks the patient's blood for the presence of antibodies to the SARS virus.
- A viral culture. In this type of test, a small amount of tissue fluid from the patient or small piece of tissue is incubated for a period of time in a special culture medium and then analyzed for measurable amounts of the SARS virus.
Treatment for SARS is largely supportive, as antibiotics are not effective in treating viruses. Although steroid medications have been used in Hong Kong and a few other locations to treat SARS patients, it is not certain whether these medications are effective. Patients are primarily treated in critical care units where they can be placed on a respirator if needed, and they are kept in strict isolation from other patients.
Patients who may have SARS should tell their doctors who their contacts have been within the past ten to fourteen days, so that these people can be evaluated for early signs of the disease.
The prognosis for recovery from SARS depends largely on the patient's age and general health. In the pandemic of 2002–2003, the highest mortality rates (over 50 percent) were among people over the age of sixty-five, whereas the overall fatality rate for the outbreak was 9.6 percent.
The most important aspect of preventing SARS is keeping patients known to have the disease in isolation from others. Other preventive measures recommended by WHO and the CDC include the following:
- Before traveling abroad, check with the CDC for any recent reports of SARS in other countries. When traveling, carry a basic first-aid kit that includes an alcohol-based hand cleanser.
- At home as well as abroad, wash the hands frequently with hot soapy water.
- If caring for a person with SARS, use disposable gloves and throw them away after use. Never try to reuse the gloves. Wear a surgical mask when in the same room as the patient.
- Wash the patient's dishes, towels, bedding, silverware, and clothing in hot water apart from the rest of the family's dishes or laundry.
- Use chlorine bleach or another household disinfectant to clean any surfaces that may have been contaminated with the patient's sweat, saliva, mucus, vomit, stool, or urine, as the SARS virus can survive for several days in human body fluids.
- Follow these safeguards for at least ten days after the last of the patient's symptoms have cleared up.
Work continues on the development of a vaccine against SARS as well as the development of possible treatments. The National Institutes of Health (NIH) has been conducting clinical trials of a SARS vaccine since 2004. Some researchers are investigating the possibility that the antiviral drugs used to treat AIDS or hepatitis might be effective against the SARS virus. Other researchers are investigating interferon, an antiviral protein produced by healthy cells exposed to a virus, to see whether it might be an effective treatment for SARS.
SARS is considered a rare disease because there were slightly more than 8,000 confirmed cases worldwide between 2002 and 2004, and none have been reported since April 2004. Public health doctors do not know whether SARS is likely to reemerge at some point in the future. In addition, some researchers are concerned about the possibility that the SARS virus might be used as an agent of bioterrorism.
WORDS TO KNOW
Bioterrorism: The use of disease agents to frighten or attack civilians.
Emerging infectious disease (EID): A disease that has become more widespread around the world in the last twenty years and is expected to become more common in the future.
Pandemic: A disease epidemic that spreads over a wide geographical area and affects a large proportion of the population.
Zoonosis: A disease that animals can transmit to humans.
SEE ALSO Common cold; Influenza; Pneumonia
Abraham, Thomas. Twenty-First Century Plague: The Story of SARS. Baltimore, MD: Johns Hopkins University Press, 2005.
Emmer, Rick. Virus Hunter. Philadelphia: Chelsea House Publishers, 2006.
Centers for Disease Control and Prevention (CDC). Current SARS Situation, May 3, 2005. Available online at http://www.cdc.gov/ncidod/sars/situation. htm (accessed May 20, 2008).
Likhacheva, Anya. “Journal Discussion: SARS Revisited.” Virtual Mentor: Ethics Journal of the American Medical Association 8 (April 2006): 219–222. Available online in PDF format at http://virtualmentor.ama-assn.org/2006/04/pdf/jdsc1-0604.pdf (accessed May 19, 2008).
Reilley, Brigg, Michael Van Herp, Dan Sermand, and Nicoletta Dentico. “SARS and Carlo Urbani.” New England Journal of Medicine 348 (May 15, 2003): 1951–1952. Available online at http://content.nejm.org/cgi/content/full/348/20/1951 (accessed May 19, 2008).
Centers for Disease Control and Prevention (CDC). Fact Sheet: Basic Information about SARS. Available online at http://www.cdc.gov/ncidod/sars/factsheet.htm (updated May 3, 2005; accessed May 19, 2008).
Mayo Clinic. SARS. Available online at http://www.mayoclinic.com/health/sars/DS00501 (updated October 6, 2006; accessed May 19, 2008).
Medline Plus. Severe Acute Respiratory Syndrome (SARS). Available online at http://www.nlm.nih.gov/medlineplus/ency/article/007192.htm (updated January 29, 2007; accessed May 19, 2008).