How SARS Works

An x-ray image of a lung and viruses. — SARS is a highly contagious condition. Yuichiro Chino / Getty Images

In February of 2003, newspapers began reporting a rapidly spreading atypical pneumonia. Identified as severe acute respiratory syndrome or SARS, this highly contagious condition is once again making international news.

According to the World Health Organization (WHO), the first cases of SARS emerged in mid-November 2002 in the Guangdong Province of China. Overall, a total of 8422 probable cases were reported from 29 countries during the outbreak. Approximately 11 percent of those infected, 916 people, died. According to WHO, the last chain of human transmission was broken in early July 2003. But, two confirmed cases have been recently reported.

In this article, we'll examine the symptoms, the treatment, and the communicability of SARS, and we'll find out what is being done to cure and control the condition.

First, let's take a look at what exactly scientists think SARS is.

SARS Symptoms and Treatment

Originally, the World Health Organization (WHO) defined severe acute respiratory syndrome (SARS) as an "atypical pneumonia of unknown etiology." In other words, we recognized it as a form of pneumonia, but we didn't know its cause. However, thanks to infectious disease experts, scientists, epidemiologists and other research specialists from all over the globe we now know that SARS is caused by a new coronavirus. According to Dr. David Heymann of the World Health Organization,

This network of laboratory directors has been meeting by telephone, sharing on a secure web site for the past four and a half weeks. It is very interesting because these laboratory directors have put aside profit, certainly prestige, and national pride to work together to help put into the public domain the information that is so necessary to learn about this disease. And it has been done in record time.

SARS Symptoms

Here are the major known facts and symptoms of SARS:

The incubation period ranges from 2 to 10 days. This means that once someone has been exposed, it can take anywhere from 2 to 10 days for symptoms to occur. Some authorities have reported incubation periods of as many as 14 days, but this is not currently considered the norm.
The initial indication of infection is a fever of 100.4 degrees Fahrenheit or more (38 degrees Celsius or more). Chills, headache, muscle soreness and a general feeling of discomfort are also common.
A dry, unproductive cough develops after 3 to 7 days. The cough can be accompanied by or eventually result in hypoxemia (a condition characterized by a reduced concentration of oxygen in the blood). Approximately 10 to 20% of infected patients require some type of assistance in breathing -- either through intubation or mechanical ventilation.

SARS Treatment

Although the causeative agent has now been identified, more research is needed to identify a cure. For now, the Centers for Disease Control (CDC) and the World Health Organization (WHO) recommend that healthcare workers treat the symptoms of SARS in the same way they would handle any other unknown form of atypical pneumonia.

Although the effectiveness is uncertain, reported regimens include the administration of:

antibiotics
antiviral agents like oseltamivir or ribavirin
a combination of steroids and antimicrobials

Let's take a look at what causes SARS and some of the other possibilities scientists initially considered.

SARS Cases

Since SARS cases began popping up early this year, scientists from all over the world have been searching hurriedly for a cause. According to the CDC, scientists had found a "previously unrecognized coronavirus in patients with SARS." This coronavirus was believed to be the leading contender in the list of possibilities. On April 16, 2003, WHO confirmed that theory. Thirteen laboratories have been urgently participating in the SARS investigation. In a recent WHO SARS update, Dr. Klaus Stohr stated:

All the data have been put on the table, have been reviewed, and the colleagues have come to a consensus agreement. We can now say that the disease called SARS, which was first reported on 12 March, exactly five weeks ago, is being caused by the coronavirus. WHO will call this coronavirus SARS virus.

Named for its distinguishing crown-like appearance, coronaviruses are commonly associated with upper-respiratory disease and have, on occasion, been connected to pneumonia. What makes this unusual is that in the previous cases of related pneumonia, many of the patients had weakened immune systems. Most SARS cases have been found in adults who were healthy prior to infection. And, while coronaviruses have been a known culprit in acute sickness among animals (such as dogs, cats and pigs), this has not been common among humans. Researchers have been investigating the possibility that this coronavirus jumped between species.

This would not be the first time a disease has migrated from animal to man. All of these conditions were first evident in animals:

Buffalopox
Creutzfeldt-Jakob disease (also known as Mad Cow disease)
Ebola haemorrhagic disease
HIV-AIDS
Nipah virus

Clinical research has also detected a paramyxovirus in specimens from patients infected with SARS. Among humans, viruses in this family cause conditions such as the mumps and measles.

The presence of the paramyxovirus initially caused scientists to consider a double etiology. Perhaps SARS could be a result of the two viruses working together. Further research does not support this theory. However, it doesn't exclude the possibility that the presence of other viruses, like the paramyxovirus, could worsen a SARS patient's condition. According to Dr. Albert Osterhaus:

The conclusion today, the people in the network agreed, that the coronavirus alone is capable of causing the typical symptoms. We cannot formally exclude that other agents, such as the human metapneumovirus, and the chlamydia that has been found in China, or a number of other viruses after you have this primary infection with the coronavirus, would eventually aggravate the situation.

Now that the SARS virus has been identified, scientists can concentrate their research on developing tests to identify people infected with SARS and creating drugs to treat and cure the condition.

For now, since there is no specific antiviral treatment, the most effective combatant is control. To curtail the spread of SARS, healthcare workers are adhering to strict safety procedures. But as we've seen, the condition has already spread around the world.

Let's look at how SARS has managed to move from continent to continent.

The Spread of SARS

Much like other respiratory illnesses, SARS seems to be spread by close contact. For example, a person infected with SARS could cough or sneeze, contaminating the immediately surrounding air with tiny droplets of infected matter. Someone in close proximity of the infected person could then breathe in air that has been contaminated. Because the cause of the SARS infection is yet unknown, scientists are considering other possibilities of communication. According to the CDC, "it is possible that SARS can also spread more broadly through the air or by touching an object that has been contaminated." A recent update on the WHO Web site addresses some other possibilities:

The SARS outbreak in Hong Kong SAR has developed an unusual pattern of transmission. This pattern is different from what is being seen in the vast majority of other SARS outbreaks, and is not yet fully understood. The number of cases is continuing to increase significantly, and there is evidence that the disease has spread beyond the initial focus in hospitals.

These developments raise questions related to other routes of transmission, in addition to well-documented face-to-face exposure to droplets released when an infected person coughs or sneezes. Epidemiologiests are considering whether SARS is being transmitted in Hong Kong by some environmental means for which no satisfactory explanation has been found.

To illustrate the communicability of SARS, consider this: According to the New York Times, as of March 29th, 249 individual cases of SARS could all be traced to one man. That's an incredible amount of people infected by one person. Of those infected, 214 were medical personnel or health-care workers.

Both the CDC and the WHO are working hard to reduce the spread of SARS by informing healthcare workers and the general public about the condition. Some of the recommendations for medical personnel in direct contact with SARS patients are:

Follow standard precautions (like hand hygiene).
Wear N-95 respirators (not face-masks).
Wear a disposable gown and gloves, removing and replacing soiled items regularly.
Wear eye protection

SARS patients and the family members and healthcare workers in contact with them should take precautionary measures for at least 10 days after SARS symptoms have passed. The CDC and the WHO recommend recovering patients and people in contact with them:

Wash and disinfect hands frequently.
Wear face masks when in close contact with others.
Avoid sharing household items like cutlery, bath towels, or bedding.
Regularly cleanse and disinfect household surfaces like sinks, toilets, and countertops.
Thoroughly launder and disinfect clothing and bedding.

For much more information, visit the CDC site.

In the next section, we'll find out what else the CDC, WHO and other agencies are doing to handle the SARS threat.

Solving the SARS Mystery

Global Think Tanks

The World Health Organization (WHO), Centers for Disease Control (CDC) and many other organizations have brought hundreds of people together in an unprecedented effort to solve the SARS mystery. According to the WHO site, the WHO collaborative network of clinicians for SARS diagnosis and treatment (Canada, Germany, Hong Kong Special Administrative Region of China, Singapore, Slovenia, Spain, Switzerland, Thailand, United Kingdom and Viet Nam) is responsible for:

compiling case management data from all affected hospitals
comparing findings, including clinical, laboratory and x-ray results
developing a working archive of x-ray images to be used in comparative studies
updating the case definition and developing suggestions for clinical diagnosis
creating treatment recommendations, including discharge criteria

On March 17th, an international research network was created to bring together the resources of 11 top-level labs in 10 countries. Researchers in these labs are studying information from the collaborative network of clinicians. As a result, scientists have been able to develop two diagnostic tests. An antibody test and an immunofluorescent test have been created to look for the coronavirus that causes SARS. Most traditional antibody tests can take more than 10 days to process. According to one BBC article Artus, a biotechnology company in Germany, is currently distributing a high-speed SARS test. Reportedly, this new test takes a mere 2 hours to identify the SARS virus.

Travel Advisory

According to a recent press release, WHO now recommends that individuals should suspend travel to Hong Kong Special Administrative Region and Guangdong Province of China, unless it is absolutely necessary.

This is the first time in at least 12 years (and possibly ever) that the World Health Organization (WHO) has made this sort of recommendation because of a disease.

WHO regularly makes travel recommendations to curtail the infection of travelers by posting alerts in regard to various areas, regions and countries. Usually, the organization provides information regarding vaccinations. Because there is no vaccination or even any definitive medicinal treatment for SARS at this time, the World Health Organization really has no other choice but to advise travelers to avoid the area entirely.

The CDC and WHO continue to update their Web sites with valuable information about SARS and other infectious diseases. For more information on SARS and related topics, check out the links on the following page.