As the world grapples with the dreaded Severe Acute Respiratory Syndrome, or SARS, which has has killed more than 100 people and infected 2,750 worldwide since it surfaced in southern China late last year, the US Centers for Disease Control and Prevention has released this set of answers to frequently asked questions on the disease.

What is SARS?

SARS is a respiratory illness that has recently been reported in Asia, North America and Europe. For additional information, check the World Health Organization's SARS web site or visit other pages on CDC's SARS web site.

What are the symptoms and signs of SARS?

The illness usually begins with a 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. 

After 2 to 7 days, SARS patients may develop a dry, nonproductive cough that might  be accompanied by or progress to the point where insufficient oxygen is getting to the blood. In 10% to 20% of cases, patients will require mechanical ventilation. For more information, see the MMWR dispatch.

If I were exposed to SARS, how long would it take for me to become sick?

The incubation period for SARS is typically 2 to 7 days; however, isolated reports have suggested an incubation period as long as 10 days.

What medical treatment is recommended for patients with SARS?

CDC currently recommends that patients with SARS receive the same treatment that would be used for any patient with serious community-acquired atypical pneumonia of unknown cause. Several treatment regimens have been used for patients with SARS, but there is insufficient information at this time to determine if they have had a beneficial  effect. Reported therapeutic regimens have included antibiotics to presumptively treat known bacterial agents of atypical pneumonia. Therapy also has included antiviral agents such as oseltamivir or ribavirin. Steroids also have been administered orally or intravenously to patients in combination with ribavirin and other antimicrobials.

How is SARS spread?

The principal way SARS appears to be spread is through droplet transmission; namely, when someone sick with SARS coughs or sneezes droplets into the air and someone else breathes them in. It is possible that SARS can be transmitted more broadly through the air or from objects that have become contaminated. 

How long is a person with SARS infectious to others?

Information to date suggests that people are most likely to be infectious when they have symptoms, such as fever or cough. However, it is not known how long before or after their symptoms begin that patients with SARS might be able to transmit the disease to others.

Who is most at risk of contracting SARS?

Cases of SARS continue to be reported primarily among people who have had direct close contact with an infected person, such as those sharing a household with a SARS patient and healthcare workers who did not use infection control procedures while caring for a SARS patient.

What is the cause of SARS?

Scientists at CDC and other laboratories have detected a previously unrecognized coronavirus in patients with SARS. While the new coronavirus is still the leading hypothesis for the cause of SARS, other viruses are still under investigation as potential causes.

What are coronaviruses?

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. Coronaviruses can survive in the environment for as long as three hours.  

What evidence is there to suggest that coronaviruses may be linked with SARS?

CDC scientists were able to isolate a virus from the tissues of two patients who had SARS and then used several laboratory methods to characterize the agent. Examination by electron microscopy revealed that the virus had the distinctive shape  and appearance of coronaviruses. Tests of serum specimens from patients with SARS showed that the patients appeared to have recently been infected with this coronavirus. Other tests demonstrated that coronavirus was present in a variety of clinical specimens from patients, including nose and throat swabs. In addition, genetic analysis suggests that this new virus belongs to the family of coronaviruses but differs from previously identified coronaviruses. These laboratory results do not provide conclusive evidence that the new coronavirus is the cause of SARS. Additional specimens are being tested to learn more about this coronavirus and its link with SARS.

If coronaviruses usually cause mild illness in humans, how could this new coronavirus  be responsible for a potentially life-threatening disease such as SARS?

There is not enough information about the new virus to determine the full range of illness that it might cause. Coronaviruses have occasionally been linked to pneumonia in humans, especially people with weakened immune systems. The viruses can also cause severe disease in animals, including cats, dogs, pigs, mice, and birds.

Has new information about coronavirus changed the recommendations for medical  treatment for patients with SARS? 

The possibility that coronavirus is the cause of SARS has not changed treatment recommendations. The new coronavirus is being tested against various antiviral drugs to see if an effective treatment can be found.

Is there a test for SARS?

No 'test' is available yet for SARS; however, CDC, in collaboration with WHO and other laboratories, has developed 2 research tests that appear to be very promising in detecting antibodies to the new coronavirus.

What about reports from other laboratories suggesting that the cause of SARS may be a paramyxovirus?

Researchers from several laboratories participating in the WHO network have reported the identification of a paramyxovirus (a group of viruses including those causing mumps and measles) in clinical specimens from SARS   patients. These laboratories are still investigating the possibility that a paramyxovirus is a cause of SARS.

What should I do if I think I have SARS?

If you are ill with a fever of over 100.4°F [>38.0°C] that is accompanied by a cough or difficulty breathing or that progress to a cough and/or difficulty breathing, you should consult a health care provider. To help your health care provider make a diagnosis, tell him or her about any recent travel to regions where cases of  SARS have been reported and where you were in contact with someone who had these symptoms. 

What has CDC recommended to prevent transmission of SARS in households?

CDC has developed interim infection control recommendations for patients with suspected SARS in the household. The basic precautions outlined in this document include the following: 

-- Infection control precautions should be continued for SARS patients for 10 days  after respiratory symptoms and fever are gone. SARS patients should limit interactions  outside the home and should not go to work, school, out-of-home day care, or other public areas during the 10-day period.

-- During this 10-day period, all members of the household with a SARS patient should carefully follow recommendations for hand hygiene, such as frequent hand washing or the use of alcohol-based hand rubs.

-- Each patient with SARS should cover his or her mouth and nose with a tissue before sneezing or coughing. If possible, a person recovering from SARS should wear a surgical mask during close contact with uninfected persons. If the patient is unable to ear a surgical mask, other people in the home should wear one when in close contact  with the patient.

-- Disposable gloves should be considered for any contact with body fluids from a SARS patient. However, immediately after activities involving contact with body fluids, gloves should be removed and discarded, and hands should be washed. Gloves should not be washed or reused, and are not intended to replace proper hand hygiene.

-- SARS patients should avoid sharing eating utensils, towels, and bedding with other members of the household, although these items can be used by others after routine cleaning, such as washing or laundering with soap and hot water.  

-- Common household cleaners are sufficient for disinfecting toilets, sinks, and other surfaces touched by patients with SARS, but the cleaners must be used frequently.  

-- Other members of the household need not restrict their outside activities unless they develop symptoms of SARS, such as a fever or respiratory illness.  

What should I do if I have recently traveled to a country where cases of SARS have been reported?

You should monitor your own health for 10 days following your return. If you become ill with a fever of over 100.4°F [>38.0°C] that is accompanied by a cough or difficulty breathing or that progresses to a cough and/or difficulty breathing, you should consult a healthcare provider. To help your healthcare provider make a diagnosis, tell him or her about any recent travel to regions where cases of SARS have been reported and whether you were in contact with someone who had these symptoms.