SARS

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SARS

Severe acute respiratory syndrome (SARS) is a viral respiratory illness caused by a coronavirus, called SARS-associated coronavirus (SARS-CoV). SARS was first reported in Asia in February 2003. Over the next few months, the illness spread to more than two dozen countries in North America, South America, Europe, and Asia before the SARS global outbreak of 2003 was contained.

The SARS outbreak of 2003

According to the World Health Organization (WHO), a total of 8,098 people worldwide became sick with SARS during the 2003 outbreak. Of these, 774 died. In the United States, only eight people had laboratory evidence of SARS-CoV infection. All of these people had traveled to other parts of the world with SARS. SARS did not spread more widely in the community in the United States.

Symptoms of SARS

In general, SARS begins with a high fever (temperature greater than 100.4°F [>38.0°C]). Other symptoms may include headache, an overall feeling of discomfort, and body aches. Some people also have mild respiratory symptoms at the outset. About 10 percent to 20 percent of patients have diarrhea. After 2 to 7 days, SARS patients may develop a dry cough. Most patients develop pneumonia.

How SARS spreads

The main way that SARS seems to spread is by close person-to-person contact. The virus that causes SARS is thought to be transmitted most readily by respiratory droplets (droplet spread) produced when an infected person coughs or sneezes. Droplet spread can happen when droplets from the cough or sneeze of an infected person are propelled a short distance (generally up to 3 feet) through the air and deposited on the mucous membranes of the mouth, nose, or eyes of persons who are nearby. The virus also can spread when a person touches a surface or object contaminated with infectious droplets and then touches his or her mouth, nose, or eye(s). In addition, it is possible that the SARS virus might spread more broadly through the air (airborne spread) or by other ways that are not now known.

Signs and symptoms of SARS

The illness usually begins with a high fever (measured temperature greater than 100.4°F [>38.0°C]). The fever is sometimes associated with chills or other symptoms, including headache, general feeling of discomfort, and body aches. Some people also experience mild respiratory symptoms at the outset. Diarrhea is seen in approximately 10 percent to 20 percent of patients. After 2 to 7 days, SARS patients may develop a dry, nonproductive cough that might be accompanied by or progress to a condition in which the oxygen levels in the blood are low (hypoxia). In 10 percent to 20 percent of cases, patients require mechanical ventilation. Most patients develop pneumonia.

Cause

SARS is caused by a previously unrecognized coronavirus, called SARS-associated coronavirus (SARS-CoV). It is possible that other infectious agents might have a role in some cases of SARS.

Transmission

The primary way that SARS appears to spread is by close person-to-person contact. SARS-CoV is thought to be transmitted most readily by respiratory droplets (droplet spread) produced when an infected person coughs or sneezes. Droplet spread can happen when droplets from the cough or sneeze of an infected person are propelled a short distance (generally up to 3 feet) through the air and deposited on the mucous membranes of the mouth, nose, or eyes of persons who are nearby. The virus also can spread when a person touches a surface or object contaminated with infectious droplets and then touches his or her mouth, nose, or eye(s). In addition, it is possible that SARS-CoV might be spread more broadly through the air (airborne spread) or by other ways that are not now known.

“Close contact”

Close contact is defined as having cared for or lived with a person known to have SARS or having a high likelihood of direct contact with respiratory secretions and/or body fluids of a patient known to have SARS. Examples include kissing or embracing, sharing eating or drinking utensils, close conversation (within 3 feet), physical examination, and any other direct physical contact between people. Close contact does not include activities such as walking by a person or briefly sitting across a waiting room or office.

If I were exposed to SARS-CoV, how long would it take for me to become sick? The time between exposure to SARS-CoV and the onset of symptoms is called the “incubation period.” The incubation period for SARS is typically 2 to 7 days, although in some cases it may be as long as 10 days. In a very small proportion of cases, incubation periods of up to 14 days have been reported.

Infectivity

Available information suggests that persons with SARS are most likely to be contagious only when they have symptoms, such as fever or cough. Patients are most contagious during the second week of illness. However, as a precaution against spreading the disease, CDC recommends that persons with SARS limit their interactions outside the home (for example, by not going to work or to school) until 10 days after their fever has gone away and their respiratory (breathing) symptoms have gotten better.

Treatments

• Patients with SARS receive the same treatment that would be used for a patient with any serious community-acquired atypical pneumonia.
• SARS-CoV is being tested against various antiviral drugs to see if an effective treatment can be found.

If there is another outbreak of SARS, how can I protect myself? If transmission of SARS-CoV recurs, there are some common-sense precautions that you can take that apply to many infectious diseases. The most important is frequent hand washing with soap and water or use of an alcohol-based hand rub. You should also avoid touching your eyes, nose, and mouth with unclean hands and encourage people around you to cover their nose and mouth with a tissue when coughing or sneezing.

SARS-Associated Coronavirus

Coronaviruses are a group of viruses that have a halo or crown-like (corona) appearance when viewed under a microscope. These viruses are a common cause of mild to moderate upper-respiratory illness in humans and are associated with respiratory, gastrointestinal, liver and neurologic disease in animals.

SARS in the environment

Preliminary studies in some research laboratories suggest that the virus may survive in the environment for several days. The length of time that the virus survives likely depends on a number of factors. These factors could include the type of material or body fluid containing the virus and various environmental conditions such as temperature or humidity. Researchers at CDC and other institutions are designing standardized experiments to measure how long SARS-CoV can survive in situations that simulate natural environmental conditions.

Laboratory Testing

Several laboratory tests can be used to detect SARS-CoV. A reverse transcription polymerase chain reaction (RT-PCR) test can detect SARS-CoV in clinical specimens such as blood, stool, and nasal secretions. Serologic testing also can be performed to detect SARS-CoV antibodies produced after infection. Finally, viral culture has been used to detect SARS-CoV.

PCR test

PCR (or polymerase chain reaction) is a laboratory method for detecting the genetic material of an infectious disease agent in specimens from patients. This type of testing has become an essential tool for detecting infectious disease agents.

Serologic testing

A serologic test is a laboratory method for detecting the presence and/or level of antibodies to an infectious agent in serum from a person. Antibodies are substances made by the body’s immune system to fight a specific infection.

Viral cultures

For a viral culture, a small sample of tissue or fluid that may be infected is placed in a container along with cells in which the virus can grow. If the virus grows in the culture, it will cause changes in the cells that can be seen under a microscope.

External links

Mainstream news

• SARS in Singapore — Updated frequently by ChannelNewsAsia
• SARS?? — Lianhe Zaobao Chinese SARS news article collage
• Fighting SARS Together — People's Republic of China Xinhua News Agency
• Yahoo! News search — SARS Full Coverage from leading worldwide news organizations

SARS weblogs

• SARS Watch — award winning weblog following SARS around the globe; updated April 2003 - September 2004
• Docbear's daily SARS updates — news and analysis written by Canadian doctor

Official announcements

• Official SARS information from the World Health Organization
• Official SARS information from the United States Centers for Disease Control
• Official SARS information from the Hong Kong Department of Health
• Official SARS information from Public Health Agency of Canada
• Official SARS information from the PRC Ministry of Health (link no longer active as of 14 May 06)
• Official SARS information from the ROC (Taiwan) Center for Disease Control(link no longer active as of 14 May 06)
• Official SARS information from the Singapore Ministry of Health and Ministry of Information and the Arts
• Following their experience with SARS, the Canadians have put together an excellent exposition of the ethical principles that apply in an epidemic or pandemic, and discussion of how the were/can be applied in practice. It's available here.

SARS Resources
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