SARS Severe Acute Respiratory Syndrome

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Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton and Rishika Babburu  

Introduction

A new and rapidly progressive respiratory syndrome termed severe acute respiratory syndrome (SARS) was identified by the World Health Organization (WHO) in the Guangdong Province of China as a global threat in March of 2003.

SARS went on to spread globally over the following months to over 30 countries and became the 1st pandemic of the 21st century. Lessons learned from the SARS pandemic are currently used as a blueprint to fight the pandemic of COVID19.

Severe acute respiratory syndrome (SARS)

• A viral respiratory disease caused by a SARS-associated coronavirus.
• An airborne virus and can spread through small droplets of saliva in a similar way to the cold and influenza.
• Showed a clear capacity to spread along the routes of international air travel.
• Can also be spread indirectly via surfaces that have been touched by someone who is infected with the virus.
• Most patients identified with SARS were previously healthy adults aged 25–70 years.

Image: Colorized transmission electron micrograph of Severe Acute Respiratory Syndrome (SARS) virus particles (orange) found near the periphery of an infected cell (green).

Etiology

SARS-CoV is thought to have jumped from an animal reservoir in the horseshoe bat through an intermediate host in the palm civet and then to humans.

• Coronaviruses are named for their crown-like glycoprotein spikes on their surface.
• Coronaviruses are large single-stranded RNA viruses that have helical nucleocapsids.
• They are usually associated with humans with the common cold, though, and in animals, they’re linked with a highly virulent disease
• The genome of SARS‐CoV has been sequenced and it is not related to any of the previously known human or animal coronaviruses. It is probable that SARS‐CoV was an animal virus that adapted to human‐human transmission in the recent past.

Epidemiology

Early cases of SARS appeared to have originated in southern China (Guangdong province) as an unusual epidemic of severe pneumonia in November 2002. In 2003, an international outbreak developed involving 29 countries with 8098 cases of probable SARS and 774 (9.6%) deaths.

• The countries with the greatest number of reported cases included China, Hong Kong, Taiwan, Singapore, and Canada.
• In the US there were 27 cases (13 female and 14 male, with a median age of 36 years), 8 of which had laboratory evidence of SARS coronavirus (CoV) infection.
• There are no known cases of SARS transmission in any part of the world. The last known case in North America was identified on June 22, 2003, in Toronto, and globally on July 15, 2003, in Taiwan.
• Since then, 7 additional sporadic cases in humans have been reported: 2 laboratory-acquired in Singapore and Taiwan in 2003, and a cluster of 5 confirmed cases in China in April 2004.

Pathologenisis

Understanding the pathogenesis of SARS is difficult as most available autopsy tissues are from patients dying later in the illness, at a time when the initial viral pathology is obscured by secondary infections or changes due to ventilator therapy, steroids and other immune modulators. Despite these limitations on autopsy material, it has been possible to determine that there are two phases of SARS pneumonia.

• Within the first 10 days the histological picture is that of acute phase diffuse alveolar damage (DAD) with a mixture of inflammatory infiltrate, oedema and hyaline membrane formation. Desquamation of pneumocytes is prominent and consistent.
• After 10 days of illness the picture changes to one of organizing DAD with increased fibrosis, squamous metaplasia and multinucleated giant cells.
• The role of cytokines in the pathogenesis of SARS is still unclear.

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