Severe Acute Respiratory Syndrome (SARS) emerged in 2003 as a significant global health event. This viral respiratory illness, caused by a novel coronavirus, garnered widespread international concern. The outbreak underscored the interconnectedness of the world and the potential for new diseases to rapidly spread across borders, prompting a global public health effort.
Origin and Initial Spread
The virus, identified as SARS-associated coronavirus (SARS-CoV), first appeared in Guangdong province, China, in November 2002. Early cases involved individuals in the food industry, such as farmers and market vendors, suggesting a link to animal exposure. Investigations revealed a zoonotic jump, with masked palm civets identified as intermediate hosts that transmitted the virus to humans. These civets, often sold in live animal markets in southern China, carried the SARS-like coronavirus.
A key event in the virus’s global spread occurred at the Metropole Hotel in Hong Kong in February 2003. A physician infected with SARS-CoV, who had traveled from Guangdong, stayed at the hotel and unknowingly transmitted the virus to several other guests. These guests then traveled to various countries, including Vietnam, Singapore, and Canada, carrying the virus with them.
Symptoms and Transmission
The illness began with flu-like symptoms, usually within 2 to 7 days of exposure. Patients often experienced a high fever, sometimes accompanied by chills, headache, and body aches. Some individuals also reported mild respiratory symptoms or diarrhea early in the illness.
After the initial phase, a dry cough often developed, sometimes progressing to shortness of breath. Most patients with SARS eventually developed pneumonia. The primary mode of transmission was person-to-person through respiratory droplets produced when an infected individual coughed or sneezed. Direct contact with contaminated surfaces or objects was also a possible route of spread.
Global Public Health Response
The World Health Organization (WHO) coordinated the international response to the SARS outbreak. The organization issued a global alert on March 12, 2003, recognizing the emergence of a severe respiratory illness of unknown origin. This was followed by a heightened global health alert on March 15, officially naming the disease Severe Acute Respiratory Syndrome. The WHO’s Global Outbreak Alert and Response Network (GOARN) assisted in coordinating efforts across 115 national health services and academic institutions.
Affected countries implemented various containment strategies. These measures included prompt patient isolation, where infected individuals were separated to prevent further transmission. Strict quarantine of contacts, who were exposed but not yet symptomatic, was also widely employed to monitor for illness and prevent onward spread. Public health authorities also initiated airport screenings for fever and launched public health information campaigns to educate citizens on prevention. These non-pharmaceutical interventions stopped the spread of SARS-CoV, with WHO declaring the global outbreak contained by July 2003.
Comparison to COVID-19
The 2003 SARS outbreak and the COVID-19 pandemic, caused by SARS-CoV and SARS-CoV-2 respectively, share common viral lineage as coronaviruses that jumped from animals to humans, originating in China. Both viruses can cause severe pneumonia and respiratory distress. However, there are notable differences in their transmissibility and disease progression.
SARS-CoV was less contagious than SARS-CoV-2 because individuals with SARS were most infectious after developing severe symptoms, often when they were already hospitalized. This characteristic made containment through isolation and contact tracing more manageable. In contrast, SARS-CoV-2 can spread more easily, including from individuals with mild or no symptoms, making early detection and containment more challenging.
The case fatality rate for SARS was around 10%, which was higher than the overall fatality rate for COVID-19, estimated to be less than 1% for much of the pandemic. Despite SARS having a higher fatality rate per case, the scale of the COVID-19 pandemic has been far greater, resulting in a much higher absolute number of deaths worldwide due to its widespread transmission. Lessons from the 2003 SARS response, such as rapid international communication, coordinated surveillance, and non-pharmaceutical interventions, informed early global responses to COVID-19.