The Topic of This Month Vol.24 No.10(No.284)

Severe Acute Respiratory Syndrome (SARS)

(IASR 2003; 24:239-240)

In 2003, in the global concerns and warning against emerging/re-emerging infectious diseases, an acute pneumonia with unknown etiology broke out in an Asian country and spread to other countries. On March 12, the World Health Organization (WHO) issued a global alert on it as an infectious disease with unknown etiology and, on March 15, an objective for global vigilance followed by a proposal of a new disease criterion of Severe Acute Respiratory Syndrome (SARS), requesting international reporting and working out a counterplan. In July 2003, WHO confirmed that the last chain of transmission was cut off, but a case was found in Singapore in September 2003. In Japan, no case has occurred until now. This article summarizes the epidemiological feature of SARS learned through the global response.

SARS outbreaks in the world: SARS outbreaks, starting presumably in Guangdong Province, China around November 2002, were recognized for the first time as hospital outbreaks of atypical pneumonia in Hanoi, Viet Nam and Hong Kong in February 2003. The epidemics in Viet Nam came to an end relatively early, whereas in Hong Kong, it spread in hospitals and partly community. In addition, epidemics spread in Singapore, Taiwan, Beijing and Toronto, Canada.

When an outbreak of a disease with unknown etiology or with etiology difficult to specify occurs, the existing surveillance system of a disease with known etiology based on the confirmatory diagnosis will not be helpful to detect cases and the response will be delayed. To carry out an epidemiological investigation promptly, it is regarded that syndromic surveillance, which collects reports based on the syndromes before confirmation of the diagnosis by physicians, is more useful. In Japan, we experienced application of this method during the G8 summit in 2000 and the World Cup football games held in Korea and Japan in 2002 (see IASR, Vol. 24, No. 2).

WHO proposed each member country to initiate a global syndromic surveillance for SARS for the first time, as it was necessary to immediately collect epidemiological findings and consider countermeasure. Case definitions relied at first only on a syndromic clinical criterion, but after identification of SARS coronavirus (SARS-CoV) as the causative agent, results of laboratory tests were added as reference data. WHO, by establishing case definitions, enhanced surveillance utilizing a standard method, tried to collect information, and conducted outbreak investigation, propagation of information, releasing various guidelines, and communication and coordination with each country. WHO issued the first recommendation for travelers to affected areas to consider postponing from the reason that SARS is a worldwide health threat (see p. 247-249 of this issue).

As the etiological agent of the unknown pneumonia, from the possible re-emergence of avian influenza or the threat of emergence of a new-type influenza, the influenza laboratory network connecting WHO influenza collaborating centers including the Department of Virology III, the National Institute of Infectious Diseases (NIID) and the influenza research institutes of many countries counteracted initially, but possibility of influenza was excluded. Coordinated by WHO, the WHO Collaborative Multi-centre Research Project on SARS diagnosis was established with 11 institutes in nine different countries including Japan among this influenza research network of many countries to share information of each institute and survey for the etiological agent. As a result, a new coronavirus was identified as the etiological agent of SARS. On April 15, 2003, WHO named this coronavirus SARS-CoV (see p. 241 of this issue).

SARS gradually came to an end under the global efforts searching for the etiological agent and working out the countermeasures, and on July 5, WHO reported that no more country was listed as "recent local transmission" of SARS. The cumulative case reports from November 1, 2002 through July 31, 2003 numbered at 8,098 (deaths counted at 774) (revised September 26, 2003, see In September 2003, a case was found in Singapore; however, this was a single isolated case and the investigation found no evidence of further transmission (

SARS surveillance and response in Japan: On March 12, 2003, the Ministry of Health, Labour and Welfare (MHLW) issued a note on the occurrence of pneumonia with unknown etiology in Hanoi and Hong Kong and announced to local governments, organization councils and public, and on March 14, based on the WHO case definitions of SARS, issued the case definitions for reporting and started the SARS surveillance in Japan. Such countermeasures as medical infrastructure improvement, preparation and propagation of guidelines for patients' management and infection control in hospitals were also planned. Disclosure of information, a travel advisory to SARS-affected areas and enhancement of quarantine were also attempted (see p. 249 of this issue) and the telephone consultation system on SARS was also organized for the general citizens (see p. 257 of this issue). On March 15, the Infectious Disease Surveillance Center (IDSC), NIID uploaded "urgent information about SARS" on the website of IDSC ( to start providing information in Japanese concerning SARS (see p. 250 of this issue).

In the Law Concerning the Prevention of Infectious Diseases and Medical Care for Patients of Infections (the Infectious Diseases Control Law), it was decided to deal with SARS as a New Infectious Disease on April 3 and official response under the Infectious Diseases Control Law was started. On July 14, it was designated by government ordinance as a Specially Designated Infectious Disease (see p. 249 of this issue). In August 2003, Section of Infectious Diseases, Health Science Council of MHLW, proposed to list SARS as the category I Notifiable Infectious Diseases in the Infectious Diseases Control Law.

The urgent international aids provided by Japan include, sending experts to Viet Nam, Hong Kong, China, Philippines and WHO Western Pacific Regional Office for the investigation and prevention of spreading infection (see p. 251-255 of this issue), and supply of goods for nosocomial infection control to each country.

In Japan, notified cases from physicians after start of the SARS surveillance totaled at 68 with a peak during the first half of April (52 suspect cases and 16 probable cases)(see IASR, Vol. 24, No. 7). Except two close contacts of a suspect and a probable cases, all were imported cases and their destinations were Taiwan, Hong Kong, the mainland China (mostly Guangdong Province), and Singapore, in order of frequency. The sex ratio was 3.0 with males outnumbering, and their ages were 30s in 25%, 20s in 19%, 40s in 18%, and under 10 years in 16%. In Japan, the National SARS Surveillance Committee was established in MHLW to verify all the cases reported so far including the follow-up data. Until now, all cases have fulfilled the conditions to exclude non-SARS; 1. Conditions explained by other diagnosis. 2. Conditions showing an improvement within three days under standard antibiotic treatment (probability of such other diseases as bacterial infection which respond to antibiotics is high). So, the number of probable cases reported to WHO was corrected to zero. In June 2003, a visitor (a physician) became symptomatic after arriving in Japan, and was hospitalized after returning to Taiwan. @However, this case was not diagnosed in Japan and not included in the case report from Japan. On this occasion, joint investigation by the local governments, MHLW and NIID did not find any secondary case from contact tracing (see p. 256 of this issue).

As SARS diagnostic test became available, cultured cells for isolation of SARS-CoV in April 2003 and in May positive control cDNA for RT-PCR were provided to prefectural and municipal public health institutes (PHIs) concerned and the laboratory systems by PHIs and NIID were accomplished. NIID examined 158 specimens for SARS diagnosis and no case was found positive (see p. 243 of this issue). It means that there was no confirmed symptomatic SARS-CoV infected case. However, some problems in diagnosis of SARS must be solved: SARS diagnostic test has not been done in all cases and confirmation of acute and convalescent antibody titers was performed with only a part of cases because only few paired serum samples were submitted for examination.

Transmission route of SARS: SARS-CoV is transmitted mainly by person-to-person infection and droplet infection from respiratory tract secretion and contact infection are also regarded as important transmission routes. The possibility of fecal-oral infection and airborne infection cannot be ruled out completely but such may be low in frequency. From the past infection, the most risky action may be close contact with a SARS case, e.g., nursing and care of SARS patient showing pneumonia, living together with symptomatic cases, or direct contact to body fluids or respiratory tract secretions of a case. Many of patients are secondarily infected persons such as medical staffs and family members of a SARS patient are important. The most important problem is spreading in a medical institute treating symptomatic patients and a leak to community wherefrom. The severer is the disease, the higher is the infectivity, particularly those in the critical course of pneumonia. Therefore, in medical facilities treating patients, countermeasures against nosocomial infection are very important. The infectivity of such a case with fever and cough may be not high but needs precaution. The infectivity during the incubation or asymptomatic period is zero or very low, if there is any. The possibility to expand to a community is usually regarded to be very low.

Conclusion: Attention to SARS was awakened by global alert by WHO and its etiological agent and the counteraction were looked for in a worldwide scale. The etiological agent was found out for an exceptionally short period and new knowledge is being accumulated. In Japanese administration, SARS was the first example of an emerging infectious disease in compliance with the Infectious Disease Control Low enacted in April 1999, and it became a specially designated infectious disease after finding the etiological agent. The epidemics ceased once in July; nevertheless, the final answer is not yet available whether this resulted from the success of counteract in each country with leading by WHO. The emergence of SARS raised many issues in infectious disease control, public health administration and medical infrastructure at present when international air travel is progressed. Some parts were rapidly and other parts were slowly improved but many parts have been left unsolved yet. Countermeasure against individual disease such as SARS is important, but intensifying the countermeasure against all infectious diseases is more important in preventing spread of infectious diseases.

In Japan, isolation of influenza viruses from overseas travelers with respiratory symptoms during July-September 2003 have been reported by PHIs (see p. 258-260 of this issue). Toward the coming influenza season, etiological diagnosis of influenza is important for counteraction against influenza but also for differentiation from SARS.

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