Severe acute respiratory syndrome epidemiology and demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Epidemiology and Demographics

Outbreak in Mainland China

Probable cases of SARS by country, 1 November 2002–31 July 2003.
Country or Region	Cases	Deaths	Fatality (%)
People's Republic of China *	5327(Official claimed Data)	349(Official claimed Data)	6.6(Official claimed Data)
Hong Kong *	1755	299	17
Canada	251	43	17
Taiwan *	346**	37	11
Singapore	238	33	14
Vietnam	63	5	8
USA	27	0	0
Philippines	14	2	14
Germany	9	0	0
Mongolia	9	0	0
Thailand	9	2	22
France	7	1	14
Malaysia	5	2	40
Sweden	5	0	0
Italy	4	0	0
UK	4	0	0
India	3	0	0
Republic of Korea	3	0	0
Indonesia	2	0	0
South Africa	1	1	100
Macau *	1	0	0
Kuwait	1	0	0
Republic of Ireland	1	0	0
Romania	1	0	0
Russian Federation	1	0	0
Spain	1	0	0
Switzerland	1	0	0
Total	8096	774	9.6
(*) Figures for the People's Republic of China (excluding the Special Administrative Regions), Macau SAR, Hong Kong SAR, and the Republic of China (Taiwan) were reported separately by the WHO.
(**) Since 11 July 2003, 325 Taiwanese cases have been 'discarded'. Laboratory information was insufficient or incomplete for 135 discarded cases; 101 of these patients died.
Source:WHO.

The epidemic of SARS appears to have originated in Guangdong Province, China in November 2002. The first case was reportedly originated from a rural area in Foshan, Guangdong in Nov 2002, and the patient, a farmer, was treated in the First People's Hospital of Foshan. The patient died soon after, and no definite diagnosis was made on his cause of death. ("Patient #0" -- first reported symptoms -- has been attributed to Charles Bybelezar of Montreal, Canada) and, despite taking some action to control it, Chinese government officials did not inform the World Health Organization of the outbreak until February 2003, restricting media coverage in order to preserve public confidence. This lack of openness caused delays in efforts to control the epidemic, resulting in criticism of the People’s Republic of China (PRC) from the international community. The PRC has since officially apologized for early slowness in dealing with the SARS epidemic.

The first clue of the outbreak appears to be November 27, 2002 when Canada's Global Public Health Intelligence Network (GPHIN), an electronic warning system which is part of the World Health Organization's (WHO) Global Outbreak and Alert Response Network (GOARN), picked up reports of a "flu outbreak" in China through internet media monitoring and analysis and sent them to the WHO. Subsequently, the WHO requested information from Chinese authorities on December 5 and 11. Importantly, while GPHIN's capability had recently been upgraded to enable Arabic, Chinese, English, French, Russian and Spanish translation, the system was limited to English or French in presenting this information. Thus, while the first reports of an unusual outbreak were in Chinese, an English report was not generated until January 21, 2003.

In early April, there appeared to be a change in official policy when SARS began to receive a much greater prominence in the official media. Some have directly attributed this to the death of American James Earl Salisbury. However, it was also in early April that accusations emerged regarding the undercounting of cases in Beijing military hospitals. After intense pressure, PRC officials allowed international officials to investigate the situation there. This revealed problems plaguing the aging mainland Chinese healthcare system, including increasing decentralization, red tape, and inadequate communication.

In late April, revelations occurred as the PRC government admitted to underreporting the number of cases of SARS due to the problems inherent in the healthcare system. Dr. Jiang Yanyong exposed the coverup that was occurring in China, at great personal risk. He reported that there were more SARS patients in his hospital alone than were being reported in all of China. A number of PRC officials were fired from their posts, including the health minister and mayor of Beijing, and systems were set up to improve reporting and control in the SARS crisis. Since then, the PRC has taken a much more active and transparent role in combating the SARS epidemic.

Spread to other countries

The epidemic reached the public spotlight in February 2003, when an American businessman traveling from China became afflicted with pneumonia-like symptoms while on a flight to Singapore. The plane stopped at Hanoi, Vietnam, where the victim died in the French Hospital of Hanoi. Several of the medical staff who treated him soon developed the same disease despite basic hospital procedures. Italian doctor Carlo Urbani identified the threat and communicated it to WHO and the Vietnam government. The severity of the symptoms and the infection of hospital staff alarmed global health authorities fearful of another emergent pneumonia epidemic. On March 12, 2003, the WHO issued a global alert, followed by a health alert by the United States Centers for Disease Control and Prevention (CDC). Local transmission of SARS took place in Toronto, Vancouver, San Francisco, Ulan Bator, Manila, Singapore, Hanoi, Republic of China, Taiwan, the Chinese provinces of Guangdong, Jilin, Hebei, Hubei, Shaanxi, Jiangsu and Shanxi, the Direct-controlled municipality of Tianjin, the Chinese Autonomous Region of Inner Mongolia, and the Chinese Special Administrative Region of Hong Kong.

In Hong Kong the first cohort of affected people were discharged from the hospital on March 29, 2003. The disease spread in Hong Kong from a mainland doctor on the 9th floor of the Metropole Hotel in Kowloon Peninsula, infecting 16 of the hotel visitors. Those visitors traveled to Singapore and Toronto, spreading SARS to those locations. Another, larger, cluster of cases in Hong Kong centred on the Amoy Gardens housing estate. Its spread is suspected to have been facilitated by defects in the sewage system of the estate.

Mortality rate

The mortality rates vary across countries and reporting organizations. In early May, for consistency with similar metrics of other diseases, the World Health Organization (WHO) and U.S. Centers for Disease Control and Prevention were quoting 7%, or the number of deaths divided by probable cases, as the SARS mortality rate. Others spoke in favour of a 15% figure, derived from number of deaths divided by the number who recovered, saying it reflects the real situation more accurately. As the outbreak progressed both mortality measures approached 10%.

One reason for the difficulties in plotting a reliable mortality figure is that the number of infections and the number of deaths are increasing at different rates. A possible explanation involves a secondary infection as a causal agent in the disease , but whatever the cause, the mortality numbers are bound to change.

Mortality by age group as of 8 May 2003 is below 1% for people aged 24 or younger, 6% for those 25 to 44, 15% in those 45 to 64 and more than 50% for those over 65.

For comparison, the case fatality rate for influenza is usually about 0.6% (primarily among the elderly) but can rise as high as 33% in locally severe epidemics of new strains. The mortality rate of the primary viral pneumonia form is about 70%.

References

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