SARS CoV is the coronavirus responsible for the severe acute respiratory syndrome outbreak in 2002–2003. It is an enveloped, positive‑sense, single‑stranded RNA virus belonging to the Betacoronavirus genus of the Coronaviridae family.
Background and Virology
Severe acute respiratory syndrome coronavirus (SARS CoV) emerged in late 2002 in Guangdong, China. Genetic analyses identified the virus as a lineage B betacoronavirus with a genome of approximately 29,700 nucleotides. SARS CoV has a large RNA genome capped at the 5′ end and polyadenylated at the 3′ end. The virion is spherical to pleomorphic, about 80–120 nm in diameter, with a lipid envelope studded by club‑shaped spike (S) glycoproteins that mediate attachment to host cells. The viral S protein recognizes the angiotensin‑converting enzyme 2 (ACE2) receptor on human epithelial cells, initiating membrane fusion and entry. Once inside, the replicase gene is translated to produce a polyprotein that is cleaved into nonstructural proteins forming the replication complex. SARS CoV replicates in the cytoplasm, generating full‑length genomic RNA and subgenomic mRNAs that direct synthesis of structural proteins. Virions assemble in the endoplasmic reticulum–Golgi intermediate compartment and are released by exocytosis. Phylogenetic studies suggest a bat origin; palm civets acted as intermediate hosts during the zoonotic spillover. Before the 2002–2003 outbreak, SARS CoV was unknown in humans, and its appearance highlighted the potential for animal coronaviruses to adapt to new species. The virus is capable of causing a severe lower respiratory tract infection characterized by fever, cough and pneumonia, with mortality around 9.6%. Human to human transmission occurs via respiratory droplets and close contact, but containment measures, including isolation and travel restrictions, eventually ended the outbreak by July 2003.
Key Facts and Outbreak Data
The SARS outbreak began in November 2002 and rapidly spread to 29 countries. According to the World Health Organization, there were 8,096 laboratory‑confirmed cases and 774 deaths worldwide. The virus spread primarily in healthcare settings, with several superspreading events linked to hospitals in Hong Kong, Toronto and Singapore. Genome sequencing during the outbreak showed minimal sequence variation, consistent with a recent spillover from animals. After July 2003, sustained human transmission ceased, but a few laboratory accidents in 2004 caused small clusters that were quickly contained. The SARS experience prompted improvements in global public health surveillance, infection control practices and research into coronavirus biology.
SARS CoV is a lineage B betacoronavirus that emerged from animal reservoirs, causing a significant but short‑lived global outbreak of severe pneumonia. It highlighted the ease with which novel coronaviruses can cross species barriers and the importance of preparedness and rapid containment. Although SARS CoV has not re‑emerged in humans since 2004, its legacy continues to inform responses to later threats.
Related Terms: MERS CoV, SARS CoV 2, Betacoronavirus, ACE2 receptor, Zoonotic diseases