Anticipated and current preventive behaviors in response to an anticipated human-to-human H5N1 epidemic in the Hong Kong Chinese general population

As of December 7, 2006, bird-to-bird transmission of the H5N1 virus have been reported in over 50 countries [1], totaling 274 reported cases of bird-to-human transmission, with 167 resulting deaths [2]. From May to December, 1997, the first 18 cases of human H5N1 were reported in Hong Kong, resulting in 6 fatalities [2]. While human-to-human transmissions are considered rare occurrences [3, 4], experts are concerned that a pandemic may occur via human-to-human transmissions [5, 6], and it has been estimated that 7.4 million deaths may result worldwide [7].

During the SARS epidemic, preventive measures were commonly practiced [8] and a number of these behaviors [9‐11] have been sustained by a large proportion of the public even after the SARS epidemic subsided in Hong Kong [12]. Preventive behaviors such as face mask use and handwashing have been suggested to be effective in the control of the SARS epidemic [9]. Understanding the correlates of these behavioral changes would facilitate formulation of policies and campaigns to promote appropriate behavioral responses in the event of a human-to-human H5N1 outbreak.

This study investigated the prevalence of self-reported preventive behaviors in response to a hypothetical local outbreak of human-to-human H5N1 transmission. These behaviors included both self-protective measures as well and those protecting others from contracting the virus. Factors associated with these behaviors were investigated.

These data indicate that the majority of the Hong Kong general public would adopt preventive measures, even in the event of 2–3 reported human-to-human H5N1 transmissions in Hong Kong. During the SARS epidemic, the prevalence of similar preventive behaviors increased sharply in the initial weeks of the outbreak [13].

Currently, we estimate that reasonably half of the general population is washing their hands over 10 times a day (unpublished data). An even higher frequency of handwashing is expected if the anticipated outbreak occurs. This is consistent with the local government campaigns for promoting handwashing [15]. Handwashing has been efficacious in preventing influenza [16, 17] and SARS [9] and the vast majority of the respondents (94%) believed that it would be efficacious in preventing human-to-human avian influenza. Such a belief was, in turn, associated with anticipated higher frequency of handwashing. Handwashing may have become a commonly accepted means of preventing infectious respiratory diseases. Approximately 90% of the general population reported face mask use in public venues during the peak of the SARS epidemic [12, 13]. The majority of the respondents would do so if there was a human-to-human H5N1 outbreak in Hong Kong. Many believed that face mask use in public venues was an efficacious method of human-to-human H5N1 prevention. However, while 87.1% of the respondents reported that they would report ILI symptoms at health checkpoints as required at times of a human-to-human H5N1 outbreak, 70.8% of the respondents did not do so during the period of April 2003 to January 2004 (during and shortly after the SARS epidemic) (unpublished data) [8]. Studies have demonstrated the limited effectiveness of such measures implemented during the SARS epidemic [18, 19]. It is shown that about 90% of the general population with ILI symptoms during the SARS epidemic were wearing face masks [13], which is comparable to the results of this study showing that about 92% would wear face masks. The similarities between various public health responses related to SARS and avian influenza are reported and it is speculated that the public is modeling their responses to avian influenza outbreak to those of the SARS epidemic.

During the SARS epidemic, the reported prevalence of face mask use when having ILI while traveling abroad was not very high, indicating that a substantial proportion of the general population was not practicing behaviors directed towards protecting others [10]. This is in contrast to the results of this study, which noted very high proportion of respondents stating their intent to adopt of behaviors directed towards protecting others. The perceived severity of H5N1 may elicit more behaviors directed at protecting others.

Quarantine was an effective means contributing to the control of SARS [20, 21] but a comparatively low percentage of the respondents (73.9%) believed quarantine to be an effective public health measure for control of avian influenza, and 11.7% of the respondents would not fully comply with government quarantine policies indicates there is still a need for education. As perceived efficacy was univariately associated with anticipated compliance with any quarantine policies, dissemination of information about its efficacy may be useful. Single respondents were less likely to comply fully with quarantine policies are also generally more mobile. These people may have less support if quarantined, and this should be considered by policy makers.

From 2003 until the present, the reported fatality rate of avian influenza in human has been over 50% [22], which is markedly higher than the 9.6% case fatality of rate SARS [23]. However, only about 40% of the study's respondents considered human-to-human H5N1 fatality rate to be higher than that of SARS. Hence, the actual magnitude of behavioral responses might be even stronger, since we found perceived fatality to be significantly associated with self-protective behaviors. It is particularly interesting to note that while associations with self-protective behaviors such as mask use and handwashing were highly significant, perceived fatality rate in comparison to SARS was not significantly associated with any of the 4 behaviors directed to protecting others. Therefore, different considerations may be involved in making decisions of whether to practice preventive behaviors, depending on whether such behaviors are self-directed or directed towards others.

With full population compliance with quarantine policies, the critical battle front of the avian influenza epidemic would shift to effective hospital infection control. It is unlikely that health care workers will be able to comply to all the stringent occupational guidelines in the event of nosocomial human H5N1 outbreaks. High fatality rates may occur in these health settings if panic or widespread non-adherence to safety measures occur. Research, counseling and emergency plans are essential to ensure that front-line health care workers are psychologically prepared and that the operations of health systems will not be disrupted.

The public regarded older people, children, health care workers and food vendors as particularly at risk of contracting the virus. During the SARS epidemic, it was reported that discriminatory attitudes have been expressed toward some at-risk groups, such as health workers [24, 25]. It is worth noting that certain social groups, such as health care workers or food vendors, may be stigmatized similarly during an H5N1 influenza. Preventing or minimizing this should thus be focus of future study.

Approximately one-quarter of the respondents believed that they or their family members would likely/very likely be affected by an H5N1 outbreak whereas approximately one-third of the respondents believed this to be true for the general population. It was reported that during the SARS epidemic, the general public worried about themselves or their family members' contracting the virus [13]. This is expected to be repeated if a human-to-human avian flu outbreak occurs. These perceptions were also associated with anticipated preventive behaviors. Many studies have documented severe distress in the community during and after the SARS epidemic [11, 13] and attention should be given in reduce panic at times of a human-to-human H5N1 outbreak. With the potentially high fatality and infectivity, high level of distress in the public is expected.

Although prevalence of health-seeking behaviors are usually higher among females than males, gender was not associated with any of the studied behaviors in this study. The health threat in this case may have overridden the aforementioned gender differentials. Education level was not associated with self-directed preventive behaviors but was associated with one of the others-directed preventive behaviors. It is possible that altruism is associated with education level. The reverse was true with age. Another study indicated that higher age was associated with the more use of preventive measures [26].

In general, factors related to perceived susceptibility, perceived clinical severity of outcomes (e.g. fatality rate, perceived availability and efficacy of treatments) were associated with anticipated preventive behaviors. Such variables are the key factors prescribed by the Health Belief Model (HBM), which stated that adoption of health behaviors is a function of an individual's attitudes and beliefs about the health issue/behavior of concern [27]. These variables were significant in predicting preventive behaviors related to SARS and influenza [9, 12, 13]. The HBM is therefore applicable to understanding behaviors for preventing the spread of emerging infectious diseases.

The study has a number of limitations. First, the study was conducted using telephone surveys and some households may not have been included. In Hong Kong, however, almost all households have telephones [28] and a large number of local published studies on SARS [11] and avian influenza [11, 13, 14] have utilized this method. Second, the response rate of the study was not very high. Nevertheless, the response rate was similar to many of other published local studies [14, 28, 29]. with the distributions of 18–39 and 40–60 year age groups being very comparable to those obtained from the Census data (49.6% and 50.4%, respectively). The study's gender distribution was also comparable to the Census distributions (47.8% male and 52.0% female) [30]. Adoption of behavioral responses was self-reported and had not been validated. However, during this pre-outbreak stage, it is unlikely that social desirability strongly biased the reporting of these behaviors.

While the results of this study may have meaningful regional policy implications, caution should be given when generalizing the results of this study to other countries. It is less clear whether populations which were relatively unaffected by SARS and populations that demonstrated less frequent face mask use and other relevant public health measures would exhibit the same magnitude of intended behavioral responses as the population of Hong Kong. Cultural and perceptions factors (such as perceived efficacy of prevention means) would also result in different prevalence of behavioral responses. International comparisons are therefore also greatly warranted.

In the event of a human-to-human H5N1 outbreak, the Hong Kong public is very likely to adopt strong preventive measures in order to protect themselves and others. The magnitude of these behavioral responses may be even greater than those witnessed during the SARS epidemic and would be likely to increase if a high fatality rate or high infectivity rate were reported. These preventive behaviors may be an effective firewall to the continued spread of the virus in the community. Surveillance of public responses is an integral part of the government's H5N1 preparedness plan. It should address issues related to the potentially underestimated fatality associated with human H5N1 cases. Surveillance should also closely monitor prevalence of important public health behaviors such as quarantine compliance and cross-border preventive measures. Up-to-date surveillance information is necessary for the government to implement and make rapid adjustments these public health measures.