SARS Outbreak (2002-2003): The Century's First Pandemic Threat

The SARS outbreak of 2002-2003 was the first severe new infectious disease of the 21st century to spread internationally. Severe acute respiratory syndrome, a pneumonia caused by a previously unknown coronavirus, emerged in Guangdong province in southern China in November 2002 and, by way of a single hotel in Hong Kong, spread to 29 countries and territories. About 8,100 people fell ill and 774 died before the outbreak was contained in July 2003, and its lessons shaped responses to later epidemics, including COVID-19.

Origins in Guangdong

The first known case was a man who fell ill in the city of Foshan, Guangdong, in mid-November 2002. Over the following weeks clusters of a mysterious “atypical pneumonia” appeared in the province, often among people who handled or cooked wild animals and among the doctors and nurses who treated them. Local authorities kept the outbreak quiet, and news spread mainly through rumours, text messages and panic buying of vinegar and herbal remedies.

China officially reported 305 cases of atypical pneumonia in Guangdong to the World Health Organization (WHO) only in February 2003, and said that the outbreak was under control. It was not.

Scientists later found the virus in masked palm civets and raccoon dogs sold in Guangdong’s live animal markets, which are thought to have passed it to humans. Studies published from 2005 onwards traced its likely natural reservoir to horseshoe bats, and in 2017 researchers reported finding bat coronaviruses containing all the genetic building blocks of the SARS virus in a cave in Yunnan province.

Hong Kong and the global spread

On 21 February 2003 Liu Jianlun, a medical professor from Guangzhou who had treated SARS patients, checked into the Metropole Hotel in Kowloon, Hong Kong, for a family wedding. Already ill, he stayed on the ninth floor and infected at least 16 other guests and visitors, probably through contaminated surfaces or air in the corridor. He died in hospital in early March.

Those guests carried the virus onward. One travelled to Hanoi, where an outbreak began at the French Hospital; others took it to Singapore, Toronto and back into Hong Kong’s hospitals. Within weeks there were outbreaks on several continents, nearly all linked by a single chain of infection that had passed through one hotel floor.

In Hanoi, the Italian WHO physician Carlo Urbani was among the first to recognise that this was a new and dangerous disease. He alerted the WHO and persuaded the Vietnamese authorities to take strong measures, which helped Vietnam become one of the first countries to stop transmission. Urbani himself caught the infection and died in Bangkok on 29 March 2003, aged 46.

The WHO response

On 12 March 2003 the WHO, then led by Director-General Gro Harlem Brundtland, issued a global alert about cases of severe atypical pneumonia. Three days later it named the disease SARS and issued an emergency travel advisory. On 2 April it advised against all but essential travel to Hong Kong and Guangdong, the first such advisory in its history; similar advice later covered Beijing, Toronto and other areas.

An international network of laboratories, set up by the WHO and sharing data in real time, worked on the cause. On 16 April 2003 the WHO announced that a new coronavirus, later named SARS-CoV, was the cause of SARS. Until then, coronaviruses had been known mainly as a cause of common colds.

In China, the turning point came in April 2003. A retired military surgeon, Jiang Yanyong, publicly stated that the number of cases in Beijing’s hospitals was far higher than officially reported. On 20 April the government admitted many more cases, and the health minister and the mayor of Beijing were dismissed. A nationwide campaign of quarantine and screening followed, and a 1,000-bed field hospital was built at Xiaotangshan outside Beijing in about a week.

Hong Kong, Toronto and Singapore

Hong Kong suffered the worst outside the mainland. In late March more than 300 residents of the Amoy Gardens housing estate fell ill, in a cluster that investigators linked to faulty drainage that allowed virus-laden droplets to rise through bathroom floor drains. Hospitals were overwhelmed, and health workers made up a large share of the victims. In all, Hong Kong recorded 1,755 cases and 299 deaths.

Toronto had the largest outbreak outside Asia. It began with a woman who had stayed at the Metropole and died at home in early March, and it spread through several hospitals. After the city seemed to have contained it, a second wave appeared in May. Canada recorded 251 probable cases and 43 deaths, and thousands of people were asked to stay in home quarantine. A WHO travel advisory against Toronto, issued on 23 April and lifted on 29 April, angered Canadian officials.

Singapore used strict measures, including temperature screening, electronic monitoring of quarantined people and the designation of a single hospital for SARS patients. It recorded 238 cases and 33 deaths.

By the numbers

Figures are from the WHO’s summary of probable cases from 1 November 2002 to 31 July 2003. Around one in five cases worldwide were health workers. The overall case fatality rate was about 10 per cent, but more than 50 per cent among patients over 65.

How SARS was stopped

There was no vaccine and no proven treatment. SARS was contained with old-fashioned public-health tools: finding and isolating patients, tracing and quarantining their contacts, strict infection control in hospitals, and screening travellers at airports. These worked partly because of the virus’s own characteristics. Most people were infectious only once they were clearly ill, and most transmission happened in hospitals and households rather than in the wider community.

On 5 July 2003 the WHO announced that the last known chain of human-to-human transmission, in Taiwan, had been broken. A few further cases occurred in 2003-2004, including laboratory infections in Singapore, Taiwan and Beijing and several community cases in Guangdong, but the disease has not been seen since 2004.

Consequences and legacy

SARS caused economic losses across East Asia estimated in the tens of billions of US dollars, as tourism, air travel and retail collapsed in the spring of 2003. It also exposed the dangers of concealing outbreaks. In 2005 the WHO adopted revised International Health Regulations, in force from 2007, which require countries to report potential public health emergencies of international concern promptly. Canada created the Public Health Agency of Canada in 2004, and Hong Kong established its Centre for Health Protection the same year.

The outbreak also made habits such as wearing face masks in public common in Hong Kong and other parts of East Asia. When the related virus SARS-CoV-2 emerged in 2019, the places that had lived through SARS were among the quickest to respond to the COVID-19 pandemic. SARS was followed by other new respiratory threats, including the 2009 swine flu pandemic, and is often compared with the far deadlier Spanish flu of 1918 as a case study in how epidemics spread through connected societies.

Timeline

• 2002, 16 November: The first known case of SARS falls ill in Foshan, Guangdong.
• 2003, 11 February: China reports 305 cases of atypical pneumonia in Guangdong to the WHO.
• 2003, 21 February: Liu Jianlun checks into the Metropole Hotel in Hong Kong.
• 2003, 12 March: The WHO issues a global alert.
• 2003, 29 March: Carlo Urbani dies of SARS in Bangkok.
• 2003, 2 April: The WHO advises against non-essential travel to Hong Kong and Guangdong.
• 2003, 16 April: The WHO confirms a new coronavirus as the cause of SARS.
• 2003, 20 April: China admits far more cases in Beijing; the health minister is dismissed.
• 2003, 5 July: The WHO declares that SARS has been contained.

Why it matters

SARS showed how quickly a new virus could travel the world by air, and how much harm secrecy could do. It was also a success story for international cooperation and basic public-health measures. Its lessons on reporting, isolation, hospital infection control and global surveillance became the foundation for responses to later coronaviruses and pandemics.