Severe acute respiratory syndrome is a viral respiratory disease caused by SARS-coronavirus (SARS-CoV-1), a respiratory virus that spreads along respiratory routes [1]. It was the first documented coronavirus to cause an acute epidemic in humans [2].
Disease overview
Evidence-backed information EN 5/7 applicable sections · ZH 5/7 applicable sections Updated Oct 23, 2026
SARS is a viral respiratory disease caused by SARS-CoV-1, a coronavirus first identified in late February 2003 during an outbreak that began in China in November 2002 and spread to 28 other countries [1]. It was the first severe and readily transmissible new disease of the 21st century, and it remains a priority pathogen owing to re-emergence risk [1][2]. The outbreak was brought under control through WHO-coordinated international investigation and response [1].
Read the full clinical and epidemiological profile 6
The incubation period of SARS is usually 2–7 days and may extend to 10 days [1]. The initial symptoms were not fully described in the available evidence, but the disease is characterized by high lethality with a case-fatality ratio of approximately 9.6% to 10.9% among confirmed cases [1][2]. Severe disease and death were associated with age and existing comorbidities [2].
SARS cases were first detected in November 2002 in China and subsequently spread to 28 other countries via international air travel [1]. The disease affected mostly previously healthy adults aged 25–70 years, with a few suspected cases among children under 15 [1]. Estimated transmissibility showed a reproduction number range of 1.1–4.59, and roughly 91% of infections were attributed to 20% of the most infectious individuals through superspreading events [2]. The case fatality among WHO-defined confirmed cases was around 9.6% to 10.9% [1][2].
SARS-CoV-1 spreads through the air via small infectious respiratory particles and can also be transmitted indirectly when the virus is deposited on surfaces by an infected person and later touched by others [1]. Transmission occurs along respiratory routes, with infection risk highest among health-care workers and close contacts of infected individuals [1][2]. Superspreading events played a major role in propagation of the epidemic [2].
Following the emergence of COVID-19, evidence-based guidance was published that is considered largely applicable to SARS as well [1]. Specific SARS-only prevention measures are not detailed in the available evidence beyond this cross-applicability of coronavirus control guidance [1].
- 1 World Health Organization. Severe Acute Respiratory Syndrome (SARS) [Internet]. cited 1 Sept 2026. Available from: https://www.who.int/health-topics/severe-acute-respiratory-syndrome
- 2 Morgenstern C et al. Severe acute respiratory syndrome (SARS) mathematical models and disease parameters: a systematic review. Lancet Microbe. 2025 Sep. PMID: 40713974. doi: 10.1016/j.lanmic.2025.101144. PubMed: https://pubmed.ncbi.nlm.nih.gov/40713974/
- U04
- 1D65
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