Environmental transmission of SARS at Amoy Gardens

Recent investigations into the March 2003 outbreak of SARS in Hong Kong have concluded that environmental factors played an important role in the transmission of the disease. These studies have focused on a particular outbreak event, the rapid spread of SARS throughout Amoy Gardens, a large, private apartment complex. They have demonstrated that, unlike a typical viral outbreak that is spread through person-to-person contact, the SARS virus in this case was spread primarily through the air. High concentrations of viral aerosols in building plumbing were drawn into apartment bathrooms through floor drains. The initial exposures occurred in these bathrooms. The virus-laden air was then transported by prevailing winds to adjacent buildings at Amoy Gardens, where additional exposures occurred. This article reviews the results of the investigations and provides recommendations for maintenance and other measures that building owners can take to help prevent environmental transmission of SARS and other flulike viruses in their buildings.     

Viral load distribution in SARS outbreak

An unprecedented community outbreak of severe acute respiratory syndrome (SARS) occurred in the Amoy Gardens, a high-rise residential complex in Hong Kong. Droplet, air, contaminated fomites, and rodent pests have been proposed to be mechanisms for transmitting SARS in a short period. We studied nasopharyngeal viral load of SARS patients on admission and their geographic distribution. Higher nasopharyngeal viral load was found in patients living in adjacent units of the same block inhabited by the index patient, while a lower but detectable nasopharyngeal viral load was found in patients living further away from the index patient. This pattern of nasopharyngeal viral load suggested that airborne transmission played an important part in this outbreak in Hong Kong. Contaminated fomites and rodent pests may have also played a role.     

Possible meteorological influence on the severe acute respiratory syndrome (SARS) community outbreak at Amoy Gardens, Hong Kong

The largest community outbreak of Severe Acute Respiratory Syndrome (SARS) occurred in the Amoy Gardens residential estate in Hong Kong, in March and April of 2003. It affected more than 300 residents, or 1.7 percent of the total Amoy Gardens population. An airborne pathway has been hypothesized as a possible mode for the spread of the disease. If that hypothesis is correct, meteorological factors may have played a contributory role; the virus-laden aerosols may have been transported between apartment blocks by the ambient wind, low mixing heights may have prevented the efficient dispersion of the aerosols, and a fall in temperature may have fostered the survival of the virus or increased the susceptibility of the exposed population. This information, used in combination with weather forecasts available several days ahead from meteorological services, should be useful for mitigation considerations in the unlikely event of a similar occurrence.     

A tale of two cities: community psychobehavioral surveillance and related impact on outbreak control in Hong Kong and Singapore during the severe acute respiratory syndrome epidemic.

OBJECTIVES: To compare the public's knowledge and perception of SARS and the extent to which various precautionary measures were adopted in Hong Kong and Singapore. DESIGN: Cross-sectional telephone survey of 705 Hong Kong and 1,201 Singapore adults selected by random-digit dialing. RESULTS: Hong Kong respondents had significantly higher anxiety than Singapore respondents (State Trait Anxiety Inventory [STAI] score, 2.06 vs 1.77; P < .001). The former group also reported more frequent headaches, difficulty breathing, dizziness, rhinorrhea, and sore throat. More than 90% in both cities were willing to be quarantined if they had close contact with a SARS case, and 70% or more would be compliant for social contacts. Most respondents (86.7% in Hong Kong vs 71.4% in Singapore; P < .001) knew that SARS could be transmitted via respiratory droplets, although fewer (75.8% in Hong Kong vs 62.1% in Singapore; P < .001) knew that fomites were also a possible transmission source. Twenty-three percent of Hong Kong and 11.9% of Singapore respondents believed that they were "very likely" or "somewhat likely" to contract SARS during the current outbreak (P < .001). There were large differences between Hong Kong and Singapore in the adoption of personal precautionary measures. Respondents with higher levels of anxiety, better knowledge about SARS, and greater risk perceptions were more likely to take comprehensive precautionary measures against the infection, as were older, female, and more educated individuals. CONCLUSION: Comparative psychobehavioral surveillance and analysis could yield important insights into generic versus population-specific issues that could be used to inform, design, and evaluate public health infection control policy measures.     

Probable secondary infections in households of SARS patients in Hong Kong

Although severe acute respiratory syndrome (SARS) is highly infectious in clinical settings, SARS has not been well examined in household settings. The household and household member attack rates were calculated for 1,214 SARS case-patients and their household members, stratified by two phases of the epidemic. A case-control analysis identified risk factors for secondary infection. Secondary infection occurred in 14.9% (22.1% versus 11% in earlier and later phases) of all households and 8% (11.7% versus 5.9% in the earlier and later phases) of all household members. Healthcare workers' households were less likely to be affected. Risk factors from the multivariate analysis included at-home duration before hospitalization, hospital visitation to the SARS patient (and mask use during the visit), and frequency of close contact. SARS transmission at the household level was not negligible in Hong Kong. Transmission rates may be greatly reduced with precautionary measures taken by household members of SARS patients.     

The experience of SARS-related stigma at Amoy Gardens

Severe Acute Respiratory Syndrome (SARS) possesses characteristics that render it particularly prone to stigmatization. SARS-related stigma, despite its salience for public health and stigma research, has had little examination. This study combines survey and case study methods to examine subjective stigma among residents of Amoy Gardens (AG), the first officially recognized site of community outbreak of SARS in Hong Kong. A total of 903 residents of AG completed a self-report questionnaire derived from two focus groups conducted toward the end of the 3-month outbreak. Case studies of two residents who lived in Block E, the heart of the SARS epidemic at AG, complement the survey data. Findings show that stigma affected most residents and took various forms of being shunned, insulted, marginalized, and rejected in the domains of work, interpersonal relationships, use of services and schooling. Stigma was also associated with psychosomatic distress. Residents' strategies for diminishing stigma varied with gender, age, education, occupation, and proximity to perceived risk factors for SARS such as residential location, previous SARS infection and the presence of ex-SARS household members. Residents attributed stigma to government mismanagement, contagiousness of the mysterious SARS virus, and alarmist media reporting. Stigma clearly decreased, but never completely disappeared, after the outbreak. The findings confirm and add to existing knowledge on the varied origins, correlates, and impacts of stigma. They also highlight the synergistic roles of inconsistent health policy responses and risk miscommunication by the media in rapidly amplifying stigma toward an unfamiliar illness. While recognizing the intrinsically stigmatizing nature of public health measures to control SARS, we recommend that a consistent inter-sectoral approach is needed to minimize stigma and to make an effective health response to future outbreaks.     

Phylogenetic analysis and sequence comparisons of structural and non-structural SARS coronavirus proteins in Taiwan.

Taiwan experienced a large number of severe acute respiratory syndrome (SARS) viral infections between March and July 2003; by September of that year, 346 SARS cases were confirmed by RT-PCR or serological tests. In order to better understand evolutionary relationships among SARS coronaviruses (SCoVs) from different international regions, we performed phylogenetic comparisons of full-length genomic and protein sequences from 45 human SCoVs (including 12 from Taiwan) and two civet SCoVs. All the Taiwanese SARS-CoV strains which associated with nosocomial infection formed a monophyletic clade within the late phase of the SARS epidemic. This Taiwanese clade could be further divided into two epidemic waves. Taiwan SCoVs in the first wave clustered with three isolates from the Amoy Gardens housing complex in Hong Kong indicating their possible origin. Of the 45 human SCoVs, one isolate from Guangdong province, China, exhibited an extra 29-nucleotide fragment between Orf 10 and Orf 11--similar to the civet SCoV genome. Nucleotide and protein sequence comparisons suggested that all SCoVs of late epidemic came from human-to-human transmission, while certain SCoVs of early epidemic might have originated in animals.     

Primary care physicians in Hong Kong and Canada--how did their practices differ during the SARS epidemic?

BACKGROUND: Hong Kong and Canada have very different primary health care systems. We thus hypothesized family physicians between the two places would be different in how they protected themselves, their staff and families during the epidemic. OBJECTIVE: The purpose of this study was to explore and contrast the impact of SARS on family physicians in Hong Kong and Toronto. METHODS: A postal questionnaire was designed and sent to 183 tutors affiliated with the Chinese University of Hong Kong with 137 replies (74.8%). In Toronto, 150 questionnaires were sent to academic family physicians affiliated with the University of Toronto with 51 replies (34%). RESULTS: All agreed SARS had changed their clinical behaviour. For public health measures in the control of SARS, Hong Kong physicians were less likely to quarantined themselves (77.1% versus 19.4%, P < 0.01) or gave quarantine leave to staff (95% versus 59.7%, P < 0.01) after exposure to probable or suspected SARS. However, they were more likely to wear a mask (52.7% versus 97.7%, P = 0) during consultation, having support staff to wear masks (68.6% versus 97.8%, P = 0) and test patient's temperature (47.1% versus 68.1%, P < 0.01). CONCLUSION: There were noticeable differences in how family physicians deal with SARS between the two cities. As SARS emerged as a global disease, better understanding of practice differences among physicians from different countries would facilitate globalization of public health.     

SARS transmission among hospital workers in Hong Kong

Despite infection control measures, breakthrough transmission of severe acute respiratory syndrome (SARS) occurred for many hospital workers in Hong Kong. We conducted a case-control study of 72 hospital workers with SARS and 144 matched controls. Inconsistent use of goggles, gowns, gloves, and caps was associated with a higher risk for SARS infection (unadjusted odds ratio 2.42 to 20.54, p < 0.05). The likelihood of SARS infection was strongly associated with the amount of personal protection equipment perceived to be inadequate, having <2 hours of infection control training, and not understanding infection control procedures. No significant differences existed between the case and control groups in the proportion of workers who performed high-risk procedures, reported minor protection equipment problems, or had social contact with SARS-infected persons. Perceived inadequacy of personal protection equipment supply, infection control training <2 hours, and inconsistent use of personal protection equipment when in contact with SARS patients were significant independent risk factors for SARS infection.     

Monitoring community responses to the SARS epidemic in Hong Kong: from day 10 to day 62

STUDY OBJECTIVE: To report the evolution in perceptions and behaviours of the general public in response to the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. DESIGN: Ten similar and sequential telephone surveys were conducted during outbreak of SARS, which are classified as belonging to the first and second phases of the epidemic. SETTING: Hong Kong, China. PARTICIPANTS: 1397 Hong Kong residents between 18 and 60 years of age. MAIN OUTCOME MEASURES: Perceptions and behaviours to SARS and its prevention. RESULTS: Most of the respondents believed that SARS could be transmitted via direct body contact and droplets. About half of respondents believed that SARS was curable, which increased in the initial phase and decreased in the second phase. Perceived chance of infection was low (9%) but fear of infection in public places was high (48%). Perceived efficacy of hygiene measures (wearing a mask: 82%, hand washing: 93%, and home disinfection: 75%) remained high in both phases and the perceived efficacy of avoiding crowded place, and using public transportation, etc, increased initially and decreased in the second phase. In parallel, use of the three hygiene measures increased significantly in the first phase and remained high for wearing a mask and washing hands in the second phase. Percentages of people avoiding crowded place and public transportation significantly increased initially and decreased in the second phase. CONCLUSION: SARS related perceptions and behaviours evolved rapidly during the epidemic and Hong Kong residents quickly adopted appropriate SARS prevention measures. Timely dissemination of information seems effective in public health crises management.     

Infection control for SARS in a tertiary paediatric centre in Hong Kong

Severe acute respiratory syndrome (SARS) is an emerging infectious disease. After the appearance of an index patient in Hong Kong in February 2003, SARS outbreaks occurred rapidly in hospitals and spread to the community. The aim of this retrospective study is to evaluate the effectiveness of a triage policy and risk-stratified infection control measures in preventing nosocomial SARS infection among paediatric healthcare workers (HCWs) at the Prince of Wales Hospital, a general hospital to which children with SARS are referred in Hong Kong. The acute paediatric wards were stratified into three areas: (1) ultra high-risk area, (2) high-risk area and (3) moderate-risk area according to different risk levels of nosocomial SARS transmission. The implementation of different levels of infection control precautions was guided by this risk stratification strategy. Between 13 March and 23 June, 38 patients with probable and suspected SARS, 90 patients with non-SARS pneumonia, and 510 patients without pneumonia were admitted into our unit. All probable SARS cases were isolated in negative-pressure rooms. Twenty-six HCWs worked in the ultra high-risk area caring for SARS patients and 88 HCWs managed non-SARS patients in other ward areas. None of the HCWs developed clinical features suggestive of SARS. In addition, there was no nosocomial spread of SARS-associated coronavirus to other patients or visitors during this period. In conclusion, stringent infection control precautions, appropriate triage and prompt isolation of potential SARS patients may have contributed to a lack of nosocomial spread and HCW acquisition of SARS in our unit.     

How did general practitioners protect themselves, their family, and staff during the SARS epidemic in Hong Kong?

CONTEXT: Severe acute respiratory syndrome (SARS) is a newly emerging infectious disease and how the frontline community doctors respond to it is not known. OBJECTIVES: To explore the impact of SARS on general practitioners (GPs) in Hong Kong. DESIGN: A cross sectional survey. SETTING: Community based primary care clinics. PARTICIPANTS: 183 family medicine tutors affiliated with a local university. Postal survey sent to all tutors with a 74.8% response rate. MAIN OUTCOME MEASURES: Change of clinical behaviour and practices during the epidemic; anxiety level of primary care doctors. RESULTS: All agreed SARS had changed their clinical practices. Significant anxiety was found in family doctors. Three quarters of respondents recalled requesting more investigations while a quarter believed they had over-prescribed antibiotics. GPs who were exposed to SARS or who had worked in high infection districts were less likely to quarantine themselves (10.8% versus 33.3%; p<0.01; 6.5% versus 27.5%; p<0.01 respectively). Exposure to SARS, the infection rates in their working district, and anxiety levels had significant impact on the level of protection or prescribing behaviour. CONCLUSION: The clinical practice of GPs changed significantly as a result of SARS. Yet, those did not quarantine themselves suggesting other factors may have some part to play. As failure to apply isolation precautions to suspected cases of SARS was one major reason for its spread, a contingency plan from the government to support family doctors is of utmost importance. Interface between private and public sectors are needed in Hong Kong to prepare for any future epidemics.     

SARS related preventive and risk behaviours practised by Hong Kong-mainland China cross border travellers during the outbreak of the SARS epidemic in Hong Kong

OBJECTIVES: To investigate patterns of behaviours and attitudes related to SARS prevention in the Hong Kong cross border traveller population.Settings: A survey was carried out at the Hong Kong-China cross border checkpoint in the middle of the epidemic. PARTICIPANTS: A total of 839 Hong Kong adult residents returning to Hong Kong from mainland China were surveyed. MAIN OUTCOME MEASURES: Practice of preventive measures and relevant behaviours and attitudes. RESULTS: Around 40% of the respondents were using masks all or most of the time in public places or washing their hands frequently (>10 times per day) and about one third avoided visiting crowded places in mainland China. Such figures were however lower than those practised by the general public in Hong Kong. SARS related perceptions, such as perceived risk of transmission and efficacy, etc, were associated with mask use and not visiting crowded places, but not with hand washing, which was associated with duration of stay. Gender differences were also observed. Around 70% of the travellers would have delayed medical consultation for influenza-like illness in China; 12.7% would not wear masks during such episodes of illness. Furthermore, about 30% of the respondents used to wear masks in Hong Kong but not in mainland China. CONCLUSIONS: The findings have implications on cross border prevention of SARS. It seems that those travelling during the SARS epidemic were a "self selected" group, and they were using less preventive measures. Special attention and intervention need to be provided to travellers to prevent a second wave cross border transmission of the disease.     

SARS-related perceptions in Hong Kong

To understand different aspects of community responses related to severe acute respiratory syndrome (SARS), 2 population-based, random telephone surveys were conducted in June 2003 and January 2004 in Hong Kong. More than 70% of respondents would avoid visiting hospitals or mainland China to avoid contracting SARS. Most respondents believed that SARS could be transmitted through droplets, fomites, sewage, and animals. More than 90% believed that public health measures were efficacious means of prevention; 40.4% believed that SARS would resurge in Hong Kong; and approximately equals 70% would then wear masks in public places. High percentages of respondents felt helpless, horrified, and apprehensive because of SARS. Approximately 16% showed signs of posttraumatic symptoms, and approximately equals 40% perceived increased stress in family or work settings. The general public in Hong Kong has been very vigilant about SARS but needs to be more psychologically prepared to face a resurgence of the epidemic.     

SARS preventive and risk behaviours of Hong Kong air travellers

This study aims to investigate Severe Acute Respiratory Syndrome (SARS)-related behaviours of travellers returning to Hong Kong by air. A total of 820 travellers returning to Hong Kong by air were interviewed about their SARS-related behaviours in April 2003. Three quarters of the respondents wore a mask most/all of the time on board, 15% did so in public places at the travel destination. Perceived susceptibility to SARS at the destination predicted mask-wearing in public places and avoidance of crowded places, and perceived efficacy was a predictor for mask-wearing during flight. Approximately 16% of the respondents stated that they would delay their medical consultation for flu-like symptoms until returning to Hong Kong. Nearly 18.2% stated that they would not wear a mask in public places at the destination if they had flu-like symptoms. Education programmes, special services and effective thermal screening are required to minimize the chance of the spread of SARS by air travellers.     

Do men have a higher case fatality rate of severe acute respiratory syndrome than women do?

Severe acute respiratory syndrome (SARS) has been reported in 30 countries and regions, with a cumulative total of 8,099 probable cases and 774 deaths as of July 31, 2003, according to the World Health Organization. In Hong Kong, People's Republic of China, 1,755 SARS cases and 299 deaths had occurred as of September 22, 2003. The authors analyzed data from the Department of Health, Hong Kong SAR. The data series includes details regarding sex, age, and chronic disease history. Using data from early March to September 22, 2003, the authors found that males had a significantly (p < 0.0001) higher case fatality rate than females did, 21.9% versus 13.2%; the relative risk was 1.66 (95% confidence interval (CI): 1.35, 2.05), and it was 1.62 (95% CI: 1.21, 2.16) after adjustment for age. Subgroup analysis was conducted by excluding health care workers (n = 386) from the analysis. The overall crude relative risk of mortality was 1.41 (95% CI: 1.15, 1.74), and the adjusted relative risk was 1.48 (95% CI: 1.10, 2.00). Thus, among SARS patients, males may be more severely affected by the disease than females are. This finding could be related to a nonuniform case definition of SARS disease, a different treatment regimen, a past smoking history, work-environment factors, or gender-specific immune-defense factors, for instance.     

SARS in three categories of hospital workers, Hong Kong

We analyzed attack rates for severe acute respiratory syndrome (SARS) in three categories of hospital workers (nurses, nonmedical support staff, and other technical or medical staff) in all public hospitals in Hong Kong that had admitted SARS patients. Of 16 such hospitals, 14 had cases. The overall attack rate was 1.20%. Nonmedical support staff had the highest attack rate (2.73%). The odds ratios of group nonmedical support staff versus those of nurses and of nonmedical support staff versus other technical or medical staff were 2.30 (p < 0.001) and 9.78 (p < 0.001), respectively. The number of affected staff and attack rates were significantly correlated with the number of SARS patients admitted (r = 0.914 and 0.686, respectively). Affected patients were concentrated in three hospitals and in the earlier phase of the epidemic. Cleaning and clerical staff on hospital wards were at a much higher risk.     

Use of quarantine to prevent transmission of severe acute respiratory syndrome--Taiwan, 2003

On July 5, 2003, Taiwan was removed from the World Health Organization (WHO) list of severe acute respiratory syndrome (SARS)-affected countries. As of July 9, a total of 671 probable cases of SARS had been reported in Taiwan. On February 21, the first identified SARS patient in Taiwan returned from travel to Guangdong Province, mainland China, by way of Hong Kong. Initial efforts to control SARS appeared to be effective; these efforts included isolation of suspect and probable SARS patients, use of personal protective equipment (PPE) for health-care workers (HCWs) and visitors, and quarantine of contacts of known SARS patients. However, beginning in mid-April, unrecognized cases of SARS led to a large nosocomial cluster and subsequent SARS-associated coronavirus transmission to other health-care facilities and community settings. In response to the growing epidemic, additional measures were taken to limit nosocomial and community transmission of SARS, including more widespread use of quarantine. By the end of the epidemic, 131,132 persons had been placed in quarantine, including 50,319 close contacts of SARS patients and 80,813 travelers from WHO-designated SARS-affected areas. This report describes the quarantine measures used in Taiwan and discusses the need for further evaluation of quarantine and other control measures used to prevent SARS.     

SARS-CoV antibody prevalence in all Hong Kong patient contacts

A total of 1,068 asymptomatic close contacts of patients with severe acute respiratory (SARS) from the 2003 epidemic in Hong Kong were serologically tested, and 2 (0.19%) were positive for SARS coronavirus immunoglobulin G antibody. SARS rarely manifests as a subclinical infection, and at present, wild animal species are the only important natural reservoirs of the virus.     

Comparative stigma of HIV/AIDS, SARS, and tuberculosis in Hong Kong

This study compares public stigma towards three types of infectious diseases- human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), severe acute respiratory syndrome (SARS), and tuberculosis (TB)-tests an attribution model of stigma, and explores the relationships between stigma and public attitudes towards government policies in Hong Kong. Using a population-based telephone survey, 3011 Hong Kong Chinese adults were randomly assigned to one of the three disease conditions and were interviewed about their attitudes and beliefs towards the assigned disease. Findings showed that public stigma was the highest towards HIV/AIDS, followed by TB and SARS. Using multi-sample model structural equation modeling, we found that the attributions of controllability, personal responsibility, and blame were applicable in explaining stigma across three disease types. Knowledge about the disease had no significant effect on stigma. Participants with less stigmatizing views had significantly more favorable attitudes towards government policies related to the diseases. The study is an important attempt in understanding the attributional mechanisms of stigma towards infectious diseases. Implications for stigma reduction and promotion of public awareness and disease prevention are discussed.