Severe acute respiratory syndrome

Severe acute respiratory syndrome
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Name	Severe acute respiratory syndrome
Synonyms	SARS
Field	Infectious disease, Pulmonology
Symptoms	Fever, cough, shortness of breath
Complications	Acute respiratory distress syndrome, Pneumonia
Onset	2–10 days post-exposure
Duration	Weeks
Causes	Severe acute respiratory syndrome coronavirus (SARS-CoV)
Risks	Close contact with infected person, travel to endemic area
Diagnosis	PCR testing, Serology
Prevention	Quarantine, Hand washing, Contact tracing
Treatment	Supportive care, Mechanical ventilation
Medication	Ribavirin, Corticosteroids (efficacy debated)
Prognosis	~9.6% case fatality rate
Frequency	8,098 cases (2002–2004 outbreak)
Deaths	774

Severe acute respiratory syndrome is a viral respiratory disease caused by a coronavirus. The illness led to a major outbreak in the early 21st century, originating in Guangdong and spreading internationally. It is characterized by severe symptoms that can progress to life-threatening respiratory failure.

Signs and symptoms

The initial phase often resembles influenza, presenting with high fever, myalgia, lethargy, and headache. Gastrointestinal symptoms like diarrhea are also common. After about a week, patients typically develop a dry cough and progressive dyspnea, which may escalate to hypoxemia. A significant proportion of cases progress to viral pneumonia and acute respiratory distress syndrome, necessitating intensive care support such as mechanical ventilation. The World Health Organization case definition for surveillance included fever and respiratory symptoms alongside epidemiological links.

Cause

The disease is caused by the Severe acute respiratory syndrome coronavirus, a positive-sense, single-stranded RNA virus. This virus is a member of the Coronaviridae family, within the genus Betacoronavirus. Research indicates it is a zoonotic virus that crossed into humans, with horseshoe bats serving as the natural reservoir and civets likely acting as an intermediate host in wet markets. The virus enters cells via the angiotensin-converting enzyme 2 receptor.

Diagnosis

Diagnosis requires a combination of clinical assessment and laboratory testing. Suspected cases are evaluated based on symptoms and travel history to affected regions like Hong Kong or Toronto. Confirmatory testing primarily uses reverse transcription polymerase chain reaction on samples from nasopharyngeal swabs or sputum. Serology testing for antibodies, such as enzyme-linked immunosorbent assay, is used for retrospective confirmation. Radiographic findings on chest X-ray or CT scan often show atypical pneumonia with ground-glass opacities.

Prevention

Control of outbreaks relies on stringent public health measures. These include rapid isolation of suspected cases, quarantine of contacts, and travel restrictions from hotspots. Infection control in hospitals involves contact precautions and airborne precautions with N95 respirators. The Centers for Disease Control and Prevention and European Centre for Disease Prevention and Control issued guidelines on hand hygiene and surface disinfection. Although vaccines were researched, none were deployed during the initial outbreak.

Treatment

Management is primarily supportive, as no specific antiviral therapy has proven universally effective. Hospitalized patients often require supplemental oxygen and advanced respiratory support. Therapies like ribavirin and high-dose corticosteroids were used empirically, but their efficacy remains unproven and controversial. Research into monoclonal antibody therapies and convalescent plasma was conducted. General care includes management of sepsis and multiple organ dysfunction syndrome.

Prognosis

The overall case fatality rate was approximately 9.6%, but varied significantly by age and patient group. The rate was less than 1% for persons under 24, but rose to over 50% for those older than 65. Patients with comorbidities like diabetes mellitus or chronic hepatitis B had worse outcomes. Survivors often experienced long-term sequelae, including pulmonary fibrosis and post-traumatic stress disorder. The National Institutes of Health funded studies on long-term recovery.

Epidemiology

The first major outbreak occurred between November 2002 and July 2003, originating in Foshan. The virus spread rapidly via international air travel to over two dozen countries, with major hotspots in Beijing, Taipei, and Singapore. A notable outbreak occurred at the Prince of Wales Hospital in Hong Kong. According to final reports from the World Health Organization, the 2002-2004 epidemic resulted in 8,098 probable cases and 774 deaths. No community cases have been reported globally since 2004.

Category:Infectious diseases Category:Viral respiratory tract infections Category:Zoonoses