Severe Acute Respiratory Syndrome (SARS)

Severe acute respiratory syndrome (SARS) facts

SARS causes a decrease in white blood cells and platelet (clotting cell) counts in the blood.
SARS causes a decrease in white blood cells and platelet (clotting cell) counts in the blood.
  • SARS is the febrile "severe acute respiratory syndrome" that first appeared in 2003 and spread rapidly to more than two dozen countries across the world, infecting over 8,000 people and killing 774 before it could be contained in 2004.
  • SARS is caused by a coronavirus (SARS-CoV) that exists in bats and palm civets in Southern China.
  • This infection can be spread easily from close person-to-person contact (such as living in the same household) via respiratory droplets that come in contact with skin or mucous membranes (eyes, mouth, or nose).
  • Infected people become ill within a week of exposure. During the first week, nonspecific symptoms of a flu-like illness begin. This period is followed by a syndrome of "atypical" pneumonia, including dry cough, and progressively worsening shortness of breath with poor oxygenation.
  • Since these are nonspecific symptoms and findings, the diagnosis of SARS is only considered if the individual has also had specific risk factors within 10 days prior to illness.
  • If there are grounds for suspicion, respiratory secretions are sent for testing at the CDC.
  • There is no medication that is known to treat SARS. Treatment is supportive.
  • During the 2003 outbreak, approximately 25% of people had severe respiratory failure and 10% died.
  • The SARS outbreak in 2002-2003 was controlled solely by using public-health measures, such as wearing surgical masks, washing hands well, and isolating infected patients.
  • Two other coronavirus types are related to SARS, MERS and Wuhan coronavirus. They can cause severe infections in humans.

What is severe acute respiratory syndrome (SARS)?

SARS is an infectious respiratory illness caused by a coronavirus. The first cases of SARS occurred in late 2002 in the Guangdong Province of the People's Republic of China. Because of the contagious nature of the disease and the delayed public-health response, the epidemic spread rapidly around the globe. Final statistics from the World Health Organization showed 8,096 reported illnesses and 774 deaths.

The rapid transmission and high mortality rate (about 10%) of SARS drew international attention and concern. Fortunately, public-health efforts to identify and quarantine infected people proved highly effective. By July 2003, human-to-human transmission of SARS had stopped.

Unfortunately, future outbreaks of SARS are still possible because the virus lives in wild bats and civets in China and in laboratory cultures. In fact, there were a few human cases of SARS in 2004 as a result of laboratory accidents in the People's Republic of China. No human cases have been identified since.

The previously unknown coronavirus that causes this syndrome was first identified in Asia in early 2003, hence its name, "SARS-associated coronavirus" or SARS-CoV. As of October 2012, SARS-CoV has been added to the National Select Agent Registry, which regulates the handling and possession of bacteria, viruses, or toxins that have potential to pose a severe threat to public health and safety. The addition of SARS-CoV permits maintenance of a national database and inspection of entities that possess, use, or transfer SARS-CoV; it also ensures that all individuals who work with these agents undergo security-risk assessment performed by the Federal Bureau of Investigation/Criminal Justice Information Service.

Middle East respiratory syndrome coronavirus (MERS-CoV) is another coronavirus in humans that was identified in an outbreak in residents and travelers to the Arabian peninsula in 2012. It is not the same coronavirus as SARS-CoV, but it is similar to bat coronaviruses, and it is likely to have originated in animals as well. MERS-CoV is discussed in another article.

In late 2019, medical professionals noted yet another coronavirus outbreak. The new virus, Wuhan virus (also termed 2019-nCoV), an RNA virus related to both SARS and MERS coronaviruses, likely originated in infected animals marketed as food in Wuhan, China. The virus, like SARS, may cause moderate to severe respiratory problems in individuals and appears to spread from person to person. Most patients with the Wuhan virus require hospitalization. Within 1 month, the virus spread to at least 6 countries, including the U.S.


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What causes SARS? How is SARS transmitted?

SARS is caused by a virus referred to as "SARS-CoV" from the coronavirus genus; SARS-CoV means severe acute respiratory syndrome-associated coronavirus. Many coronaviruses infect animals and humans, and the common cold is caused by some coronaviruses and several other viruses. SARS-CoV virus had never been identified before 2002. This was not entirely surprising because there are many types of coronaviruses, and they are known to mutate easily.

SARS-CoV likely originated in wild bats and then spread to palm civets or similar mammals. The virus then mutated and adapted itself in these animals until it eventually infected humans. There was ample opportunity for the virus to come into contact with humans. Bats serve as a food source in parts of Asia, and their feces are sometimes used in folk medicines. Civets are cat-like mammals that live in the tropics of Africa and Asia and produce musk from their scent glands, which is used in perfumes. Civets are also hunted for meat in some parts of the world. These animals could easily transmit the virus to humans.

SARS-CoV is spread from person to person through respiratory secretions. SARS often affected people caring for a sick individual and spread readily through health care facilities until infection-control measures were established. SARS-CoV was isolated from many hospital surface areas, including elevator buttons, likely contributing to the spread of the disease among healthcare workers. During the outbreak, one in about every 20 infected people was a health care worker who cared for a patient with SARS; nearly 2,000 health care workers became ill.

Is SARS contagious? How long is the contagious period for SARS?

SARS is contagious from person to person by droplets in respiratory secretions, such as during coughing or sneezing, much like the common cold. In addition, droplets on surfaces can be touched and rubbed into eyes, nose, or mouth membranes. Relatively close contact is required, such as being within 3 feet of a symptomatic person while living with them, sleeping in the same room, sharing household items with them, or providing medical care for them.

The contagious period is generally from the time symptoms start (end of the incubation period) and is greatest during the second week of symptoms. People with SARS should avoid leaving home until 10 days after symptoms end due to possible contagiousness.

What is the incubation period for SARS?

The time between getting infected and the start of symptoms (the incubation period) is about two to seven days but occasionally has been up to 14 days.

What are 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 simply 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 SARS symptoms and signs?

Symptoms begin two to seven days after acquiring the virus. Initially, the illness resembles influenza and lasts for up to one week. Symptoms include fever, chills, headache, aches or pain in the muscles, general feeling of weakness (malaise), and poor appetite. Nausea, vomiting and diarrhea are less common. This period is followed by a syndrome suggesting atypical pneumonia, including dry cough and progressively worsening to severe shortness of breath (dyspnea) and inability to maintain oxygenation (hypoxia). Progression may be rapid or it may take several days. Severely affected people develop a potentially fatal form of respiratory failure, known as adult respiratory distress syndrome (ARD or ARDS). In addition to the attacking the alveoli (air sacs) in the lungs, the virus also infects other organs in the body, causing kidney failure, inflammation of the heart sac (pericarditis), or severe systemic bleeding from disruption of clotting system (disseminated intravascular coagulation), reduced lymphocyte cell counts (lymphopenia), inflammation of the arteries (vasculitis), and inflammation of the gut with diarrhea. People with compromised immune systems such as severe rheumatoid arthritis or organ transplantation may not experience respiratory symptoms but can have fever or diarrhea.

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What kind of specialists treat SARS?

Most people with SARS would see a primary-care provider or an emergency-medicine doctor as illness rapidly progressed. Depending on the stage of illness, they would be admitted to a hospital as oxygen levels decreased. In the hospital, a person with SARS would likely be managed by a hospitalist or critical-care doctor, with consultations to an infectious-disease doctor and a lung doctor (pulmonologist).

How do health care professionals diagnose SARS?

SARS-CoV is detected using enzyme-linked immunoassays (EIA) or reverse transcriptase polymerase chain reaction (PCR) tests, which are available through the CDC. These tests are performed on respiratory secretions or blood.

These tests are performed only when the patient's history makes SARS likely and usually in consultation with infectious-disease doctors, public-health authorities, and the Centers for Disease Control and Prevention. If a test is positive, it will be confirmed by the CDC. Other tests may be abnormal, but they are not specific for SARS. The chest X-ray shows pneumonia, which may look patchy at first. White blood cells and platelet (clotting cell) counts in the blood are usually decreased.

SARS should be considered in people with the appropriate symptoms who work with SARS-CoV in a laboratory or who have recent exposure to infected people or mammals in Southern China. No human cases of SARS have been reported since 2004 in the United States, so it is extremely unlikely that a patient in the U.S. will have SARS without a history of such exposure. It is possible, however, that a new outbreak might occur. Therefore, SARS (along with other similar viruses) should also be considered when there is a cluster of unusually severe pneumonia that has no other explanation.

What is the treatment for SARS?

Patients with SARS often require oxygen therapy, and severe cases require tracheal intubation and mechanical ventilation to support life until recovery begins. Severely ill patients should be admitted to the intensive-care unit. No medication has been proven to treat SARS effectively, and treatment is supportive and directed by the patient's clinical condition. Medical caregivers need to follow strict policies on gloves, masks, gowns, and other protocols to avoid becoming infected.

What is the prognosis of SARS?

During the pandemic, approximately 25% of people with SARS developed severe respiratory failure or ARDS. In the general population, people with SARS had approximately a 10% chance of dying. Deaths in children were rare. However, up to 50% of people with underlying medical conditions died. People over 50 years old also had a similar death rate. Unfortunately, many people who eventually recovered from SARS in China suffered disabling lung scarring (pulmonary fibrosis), thinning of bones (osteoporosis), and severe damage to the hip bone (femoral head necrosis).

Is it possible to prevent SARS?

Travelers to affected areas can protect themselves by taking simple measures that help prevent the spread of germs. Frequent hand washing with soap and water, or using an alcohol-based hand sanitizer, avoiding close contact with sick people, and not touching one's eyes, nose, and mouth can prevent the spread of viruses.

The SARS pandemic was brought to an end by basic public-health and infection-control measures. In the health care setting, someone with a suspected case of SARS is placed in an airborne infection isolation room (AIIR). This is a patient care room used to isolate people with suspected or confirmed airborne infectious diseases. The air is under negative pressure, meaning that contaminated air is continually sucked into the room instead of letting it leak out into the hospital environment. This air is exhausted outside, or it circulates back into the room after passing through a high-efficiency particulate air (HEPA) filter to decontaminate it. If an AIIR not available, the patient must wear a face mask and is isolated in a single-patient room with the door closed. The number of staff assigned and the patient's movements outside of the room must be minimized. Before entering the isolation room, health care workers caring for the patient must wear a gown, gloves, eye shield, and mask or a portable air purifier that filters out small infectious particles (N95 mask). Before leaving the room, any disposable gear such as gowns, gloves, and mask must be discarded. Hands must be cleansed with soap and water or an alcohol-based hand sanitizer after leaving the room and before attending to another patient.

Most public-health officials recommend isolation for anyone diagnosed with SARS-CoV.

The key to preventing another outbreak is to identify the first infected patients promptly before they have time to spread the illness more widely. People who have been exposed to an infected individual should be carefully monitored for fever or respiratory symptoms. Exposure is defined as living with or caring for an infected person, being within 3 feet of the sick person, exposure to bodily fluids, or direct physical contact. The Centers for Disease Control and Prevention does not mandate quarantine measures for exposed individuals who are otherwise healthy and allows this decision to be handled on a case-by-case basis. Local public-health authorities should be consulted promptly when the diagnosis is suspected. If a significant outbreak of SARS occurs again, people may be advised to maintain a distance from others in the community ("social distancing") by avoiding large gatherings or close contact with others. However, isolation and quarantine methods have been effective in the prevention of SARS spread.

Is there a SARS vaccine? What research is being done on SARS?

Research on a vaccine continues, but none is available yet. Most research is examining the virus itself and chemical pathways that may pose opportunities for drugs to treat it.

Where can people get more information about SARS?

Information on SARS may be obtained from the CDC or the World Health Organization:

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