Severe Acute Respiratory Syndrome (SARS) – Causes and Prevention

Overview – Severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is an infectious condition that can cause serious respiratory illness and sometimes death. SARS became a concern in 2003 when an outbreak that began in China spread worldwide causing a global epidemic. The disease was contained and there have been no cases of SARS anywhere in the world since 2004.

SARS is caused by a coronavirus, the same family of viruses that causes some common colds. Like most respiratory viruses, SARS appeared to spread from person to person through coughing, sneezing and close contact. Symptoms of the infection seen during the 2003 outbreak included those similar to the flu: fever, cough, chills, fatigue, and shortness of breath, headache, and diarrhea. The infection progressed rapidly and most people with SARS needed to be hospitalized and isolated to prevent the spread of the virus to other people, including healthcare workers.

Pathophysiology of SARS

The lungs and gastrointestinal tract have been demonstrated to be the only major organ systems that support SARS-CoV replication.

After the establishment of infection, SARS-CoV causes tissue damage by (1) direct lytic effects on host cells and (2) indirect consequences resulting from the host immune response. Autopsies demonstrated changes that were confined mostly to pulmonary tissue, where diffuse alveolar damage was the most prominent feature. (See the image below.)

Multinucleated syncytial giant cells were thought to be characteristic of SARS but were rarely seen. Angiotensin-converting enzyme-2 (ACE-2), being a negative regulator of the local rennin-angiotensin system, was thought to be a major contributor to the development of this damage.

The other mechanism was thought to be the induction of apoptosis. The SARS-CoV–3a and –7a proteins have been demonstrated to be inducers of apoptosis in various cell lines.

Immunologically, SARS is characterized by a phase of cytokine storm, with various chemokines and cytokines being elevated.

Transmission – Severe acute respiratory syndrome

SARS is an airborne virus, which means it spread in a similar way to colds and flu.

The SARS virus is spread in small droplets of saliva coughed or sneezed into the air by an infected person. If someone else breathes in the droplets, they can become infected.

SARS can also be spread indirectly if an infected person touches surfaces such as door handles with unwashed hands. Someone who touches the same surface may also become infected.

The SARS virus may also be spread through an infected person’s poo. For example, if they do not wash their hands properly after going to the toilet, they may pass the infection on to others.

Evidence from the SARS pandemic of 2002 to 2003 showed people living with or caring for someone with a known SARS infection were most at risk of developing the infection themselves.

Causes – Severe acute respiratory syndrome

SARS is caused by a member of the coronavirus family of viruses (the same family that can cause the common cold). It is believed the 2003 epidemic started when the virus spread from small mammals in China.

When someone with SARS coughs or sneezes, infected droplets spray into the air. You can catch the SARS virus if you breathe in or touch these particles. The SARS virus may live on hands, tissues, and other surfaces for up to several hours in these droplets. The virus may be able to live for months or years when the temperature is below freezing.

While the spread of droplets through close contact caused most of the early SARS cases, SARS might also spread by hands and other objects the droplets have touched. Airborne transmission is a real possibility in some cases. The live virus has even been found in the stool of people with SARS, where it has been shown to live for up to 4 days.

With other coronaviruses, becoming infected and then getting sick again (reinfection) is common. This may also be the case with SARS.

Symptoms usually occur about 2 to 10 days after coming in contact with the virus. In some cases, SARS started sooner or later after the first contact. People with active symptoms of illness are contagious. But it is not known for how long a person may be contagious before or after symptoms appear.

What are the risk factors for SARS?

SARS-CoV can infect a person regardless of their health status or age group. However, it was clear that some people were at increased risk during the 2002-2003 outbreak. This included people over the age of 50 (some reported mortality rates of about 50%), pregnant women, and those with underlying diabetes, heart disease, or liver disease. A major risk factor is a simple close association with any person infected with SARS-CoV since the virus can be spread through droplets sprayed into the air by coughing, sneezing, or even talking.

Other risk factors include the following:

• Recent travel to mainland China, Hong Kong, or Taiwan or close contact with ill people with a history of recent travel to these areas
• Employment in an occupation at risk for SARS-CoV exposure, including a health care worker with direct contact with a patient having SARS-CoV, or a worker in a laboratory that contains live SARS-CoV
• Relationship with a cluster of cases of atypical pneumonia without an alternative diagnosis

What Are the Symptoms of SARS?

SARS symptoms are similar to those of the flu, including:

• Fever over 100.4°F
• Dry cough
• Sore throat
• Problems breathing, including shortness of breath
• Headache
• Body aches
• Loss of appetite
• Malaise
• Night sweats and chills
• Confusion
• Rash
• Diarrhea

Breathing issues will appear within two to 10 days after a person is exposed to the virus. Health officials will quarantine a person who presents the above symptoms and family members if they have a history of foreign travel. The person will be quarantined for 10 days to prevent the virus from spreading.

Factors that increase your risk of contracting the disease include close contact with someone diagnosed with SARS and a history of travel to any other country with a reported SARS outbreak.

Possible Complications of SARS

Complications may include:

• Respiratory failure
• Liver failure
• Heart failure
• Kidney problems

Diagnosis and Test – SARS

Your health care provider may hear abnormal lung sounds while listening to your chest with a stethoscope. In most people with SARS, a chest x-ray or chest CT show pneumonia, which is typical with SARS.

Tests used to diagnose SARS might include:

• Arterial blood tests
• Blood clotting tests
• Blood chemistry tests
• Chest x-ray or chest CT scan
• Complete blood count (CBC)

Tests used to quickly identify the virus that causes SARS to include:

• Antibody tests for SARS
• Direct isolation of the SARS virus
• Rapid polymerase chain reaction (PCR) test for SARS virus

All current tests have some limitations. They may not be able to easily identify a SARS case during the first week of the illness when it is most important.

Treatment for Severe acute respiratory syndrome

Currently, no definitive medication protocol specific to Severe acute respiratory syndrome has been developed, although various treatment regimens have been tried without proven success. The CDC recommends that patients suspected of or confirmed as having SARS receive the same treatment that would be administered if they had any serious, community-acquired pneumonia.

Isolate confirmed or suspected patients and provide aggressive treatment in a hospital setting. Patient care precautions include contact, droplet, and airborne isolation. N95 respirators are preferred to surgical masks. Mechanical ventilation and critical care treatment may be necessary during the illness. No benefit has been shown with prone ventilation. An infectious disease specialist, a pulmonary specialist, and/or a critical care specialist should direct the medical care team. Communication with local and state health agencies, the CDC, and the WHO is critical.

Is there a vaccine?

There is currently no vaccine against SARS, but scientists are working on one.

In 2013, researchers announced that they had found a way to disable a part of the virus involved in SARS that allows it to hide from the immune system. This could lead to the development of a vaccine against the disease.

Since 2004, there have been no recorded cases of SARS anywhere in the world. Health organizations continue to work on a response, in case SARS reappears in the future.

Prevention of SARS

There’s no cure for SARS. You can lower your chances of getting it in the first place with some simple steps:

• Wash your hands often with soap and water, or use an alcohol-based hand sanitizer.
• Don’t touch your eyes, nose, or mouth with dirty hands.
• Wear disposable gloves if you have contact with someone’s pee, poop, saliva, or other body fluids.
• Wipe surfaces like countertops with disinfectants, and wash personal items with soap and hot water.
• If you’re around someone with SARS, wear a surgical mask to cover your nose and mouth.