SARS begins with a fever that usually occurs two to seven days after you've been infected, although it may not appear for up to 10 days. Initial signs and symptoms include:

• Fever, 100.4 F (38 C) or higher
• Chills
• Muscle soreness
• Headache
• General feeling of discomfort

Two to seven days after the initial signs and symptoms, you're likely to develop a dry cough. In some people, SARS may progress to severe pneumonia, leading to an insufficient amount of oxygen in the blood (hypoxemia).

You're probably most contagious while you have active signs and symptoms. As a precaution, the Centers for Disease Control and Prevention (CDC) recommends that people who have recovered from SARS avoid going out in public for 10 days after symptoms go away.

When to see a doctor
If you think you've been exposed to or have SARS, see your doctor right away. SARS is a serious illness that can lead to death. It's also important that if you have the disease, that you not spread it to others.

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SARS is caused by a strain of coronavirus, the same family of viruses that cause the common cold. Until now, these viruses have never been particularly virulent in humans, although they can cause severe disease in animals. For that reason, scientists originally thought that the SARS virus might have crossed from animals to humans. It now seems likely, however, that it evolved from one or more animal viruses into a completely new strain.

How SARS spreads
Most respiratory illnesses, including SARS, spread through droplets that enter the air when someone with the disease coughs, sneezes or talks. This type of transmission can occur in two ways:

• Droplets. In droplet transmission, the infected particles are large and can travel only about three feet. To inhale them, you must be face to face with someone who's sick.
• Airborne particles. Because airborne particles are much smaller than droplets, they travel farther and linger longer in the air. As a result, you can become infected even after the person who coughed or sneezed has left the room.

Most experts think SARS spreads mainly through face-to-face contact, but the virus also may be spread on contaminated objects, including doorknobs, telephones and elevator buttons.

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In general, people at greatest risk of SARS have had direct, close contact with someone who's infected, such as:

• A roommate or family member.
• Doctors and hospital workers who treated people with SARS before the disease was identified were some of the first SARS casualties.
• People with a variation in an immune system gene that may make them much more vulnerable to the SARS virus. The genetic variation is common among people of Southeast Asian descent but is rare in other populations. This may help explain why most SARS cases have occurred in China and Southeast Asia.

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Between 10 and 20 percent of people with SARS become progressively worse and develop breathing problems so severe that they need the help of a mechanical respirator. SARS is fatal in some cases, often due to respiratory failure. Other possible complications include heart and liver failure.

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When SARS first surfaced, no specific tests were available to help doctors diagnose the disease. Now several laboratory tests can help detect the virus, although all have some limitations. These tests include:

• DNA test (reverse transcription polymerase chain reaction test). Using secretions from your nose or a blood or stool sample, scientists look for DNA of the suspected pathogen.
• Blood test (serologic test). This checks a sample of your blood for the presence of antibodies to SARS-associated coronavirus. Antibodies are substances that your immune system produces to fight a specific infection.
• Virus test (viral culture). In this test, a small sample of tissue or fluid is placed on a special medium (culture) that's incubated for a period of time, then checked for the presence of the SARS virus.

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In spite of a concerted global effort, scientists have yet to find an effective treatment for SARS. A combination of antiviral drugs normally used to treat AIDS — lopinavir-ritonavir along with ribavirin — has been shown in clinical studies to prevent serious complications and deaths from SARS. However, further testing is needed.

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There has been no known transmission of SARS anywhere in the world since 2004. Check the CDC's SARS Information for Travelers Web site for the most current information regarding SARS activity.

Researchers are working on several types of vaccines for SARS, but until an effective vaccine is developed, the World Health Organization (WHO) and the CDC have established a number of guidelines designed to slow or stop transmission of the disease.

Protecting yourself
If you're caring for someone at home with SARS, these measures can help you stay healthy:

• Wash your hands frequently with soap and hot water or use an alcohol-based hand rub containing at least 60 percent alcohol.
• Instead of touching your face with your hands, use a disposable tissue to rub your eyes or nose.
• Wear disposable gloves if you have contact with the person's body fluids or feces. Throw the gloves away immediately after use and wash your hands thoroughly.
• Wear a surgical mask when you're in the same room as a person with SARS. Wearing glasses also may offer some protection.
• Use soap and hot water to wash the utensils, towels, bedding and clothing of someone with SARS. Don't use these items yourself until they're clean.
• Use a household disinfectant to clean any surfaces that may have been contaminated with sweat, saliva, mucus, vomit, stool or urine. Wear disposable gloves while you clean and throw the gloves away when you're done.
• Follow all precautions for at least 10 days after the person's signs and symptoms have disappeared.
• Keep children home from school if they develop a fever or respiratory symptoms within 10 days of being exposed to someone with SARS. They can return to school if signs and symptoms go away after three days.

Protecting others
If you've been diagnosed with SARS, the following measures can help prevent the infection from spreading:

• Wash your hands carefully and frequently with soap and hot water or an alcohol-based hand rub containing at least 60 percent alcohol.
• Cover your mouth and nose with a tissue when you cough or sneeze, and if possible, wear a surgical mask when you're in close contact with other people.
• Don't share your silverware, towels or bedding with anyone in your home until these items have been thoroughly washed with soap and hot water.
• Avoid going to school, work or other public places for 10 days after your signs and symptoms disappear.

Traveling safely
Consider taking the following measures to help reduce your risk of SARS when traveling:

• Buy or assemble a basic first-aid kit. Make sure the kit includes an alcohol-based hand cleaner.
• Inform yourself. Learn as much as you can about the SARS status of the countries you'll visit. You can find the latest information about SARS on the WHO and CDC Web sites.
• Make sure you're current on all of your immunizations. It's best to have any needed shots four to six weeks before your departure.
• Check your travel insurance. You may want to purchase coverage for medical evacuation if you're traveling to a country that's having a SARS or other infectious disease outbreak.
• Know where medical care will be available in the areas you visit. Take with you a list of the names, addresses and phone numbers of recommended doctors and hospitals at your destinations. Your doctor or local or state medical society, the International Association for Medical Assistance to Travellers or the U.S. State Department's Overseas Citizens Services can help provide this information.
• Avoid 'live' markets. In China, avoid visiting live food markets. Civet cats sold in these markets have been found to carry viruses similar to the SARS virus.

While traveling
Some experts believe that infections spread on airplanes through the air vents located directly above your seat. It's best to turn these vents off and to carry disposable towelettes so that you can clean your hands frequently during the flight.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.