Severe Acute Respiratory Syndrome (SARS)

Severe acute respiratory syndrome (SARS) is a viral respiratory disease caused by a SARS-coronavirus. While SARS cases were detected as early as November 2002 as part of an outbreak that emerged in China and subsequently spread to 28 other countries, the pathogen causing the disease was identified as a coronavirus at the end of February 2003. WHO coordinated the international investigation with the assistance of the Global Outbreak Alert and Response Network (GOARN) and worked closely with health authorities in affected countries to provide epidemiological, clinical and logistical support and to bring the outbreak under control.

SARS-CoV-1 (the number 1 was added later to distinguish it from the recently emerged SARS-CoV-2) is a respiratory virus which can spread through the air through small infectious respiratory particles. It was the first severe and readily transmissible new disease to emerge in the 21^st century and spread along respiratory routes and cause an epidemic through international air travel of people to other countries outside of its originating country.

SARS can also be transmitted indirectly through deposition of the virus onto surfaces via contaminated surfaces that have been touched by someone who is infected with the virus.

Most patients who contracted SARS were previously healthy adults aged 25–70 years. A few suspected cases of SARS have been reported among children under 15 years. The case fatality among persons with illness meeting the current WHO case definition for confirmed cases of SARS is around 9.6%.

Following the emergence of COVID-19, evidence-based guidance was published and can be found here. Such guidance will largely apply to SARS as well.

 

The incubation period of SARS is usually 2–7 days but may be as long as 10 days.

The first symptom of the illness is generally fever (>38°C), which is often high, and sometimes associated with chills and rigors. It may also be accompanied by other symptoms including headache, malaise and muscle pain. At the onset of illness, some cases have mild respiratory symptoms. Typically, rash and neurologic or gastrointestinal findings are absent, although a few patients have reported diarrhoea during the early febrile stage.

After 3-7 days, a lower respiratory phase begins with the onset of a dry, non-productive cough or dyspnoea (shortness of breath) that may be accompanied by, or progress to, hypoxemia (low blood oxygen levels). In 10–20% of cases, the respiratory illness is severe enough to require intubation and mechanical ventilation. Chest radiographs may be normal throughout the course of illness, though not for all patients. The white blood cell count is often decreased early in the disease, and many people have low platelet counts at the peak of the disease. 

While no treatment or cure was available at the time of the emergence of SARS, the emergence of a closely related disease – COVID-19 – lead to the rapid development of several antivirals and vaccines. Antivirals such as polymerase and protease inhibitors against SARS-CoV-2 are likely to be effective against SARS-CoV-1. COVID-19 vaccines may provide some level of cross-protection against SARS; however, the extent of such cross-protection remains to be studied.

Controlling outbreaks relies on containment measures including:

• prompt detection of cases through good surveillance networks and including an early warning system;
• isolation of suspected or probable cases;
• tracing to identify both the source of the infection and contacts of those who are sick and may be at risk of contracting the virus;
• quarantine of suspected contacts for 10 days;
• exit screening for outgoing passengers from areas with recent local transmission by asking questions and temperature measurement; and
• disinfection of aircraft and cruise vessels having SARS cases on board using WHO guidelines.

Personal preventive measures to prevent spread of the virus include frequent hand washing using soap or alcohol-based disinfectants. For those with a high risk of contracting the disease, such as health care workers, use of personal protective equipment, including a mask, goggles and an apron is mandatory.  Whenever possible, household contacts should also wear a mask.

For more information, please access SARS-CoV-2 material here.