The public health viewpoint

The SARS epidemic is already regarded as a defining moment in the evolution of communicable disease and will undoubtedly be seen as a milestone in the history of global public health. In 1969 the then US Surgeon-General confidently announced that "the book of infectious disease was now closed" and "that antimicrobial war had been won." We have since been forced to acknowledge many times over just how flawed that optimistic vision was. The history of newly emergent communicable disease during the past three decades should be a caution to any health professional or government official who is tempted to declare that we are free of the health risks presented by micro-organisms. It appears that the SARS epidemic originated in Foshan, Guangdong Province in November 2002. The epidemic then spread to the cities of Heyuan and Zhongshan before causing a large outbreak in the provincial capital of Guangzhou in January 2003 (Figure 1). It is believed that a single highly infectious index patient, also known as a "super-spreader," from Guangzhou who visited Hong Kong in mid-February and stayed at the Metropole Hotel transmitted the SARS coronavirus to a number of Hong Kong people and to 16 other tourists from Vietnam,1 Canada2 and Singapore, who in turn triggered outbreaks in their home countries. The subsequent admission and treatment of this initial cohort of infected Hong Kong people at two of Hong Kong's busiest public hospitals initiated an infectious cascade that ultimately led to 1,705 cases locally In an ideal situation, how should and could public health authorities have responded to the beginnings of this outbreak? For example, in Hong Kong, an initially small and apparently unrelated cluster of cases at Kwong Wah Hospital and Prince of Wales Hospital (PWH) provided the first indication that something unusual was happening by the third week of February. However, the World Health Organisation (WHO) did not officially declare the situation to be an outbreak until three weeks later, by which time the disease had already spread into the community and been exported to 11 other countries. What kinds of disease surveillance and communication systems were needed to alert public health practitioners to the emerging infection within days, as opposed to weeks, of its arrival into Hong Kong? Once the epidemic was acknowledged, what sorts of information were essential in guiding the formulation of public health policies? How best might such information be captured and studied? How could direct evidence of the growth potential and trajectory of the infection in the community be obtained? How long should the quarantine period be? Who should be isolated and where? How might health authorities determine whether the various personal and public hygiene measures, such as wearing of facemasks, school closures and frequent hand washing, were sufficient or could have been more effective in halting the spread of the virus, both before and after they were implemented? How might different scenarios in combating SARS on the community level, as the epidemic evolved, be modelled to better prepare for future outbreaks? While these and related questions may not have the same popular appeal as the microbiological detective stories of the discovery of the SARS coronavirus, or the apparent immediacy of developing a vaccine, they are nonetheless crucial in the control of any epidemic. SARS has been no exception. The world has contained the present outbreak not because of genetic breakthroughs or high-technology solutions, but through painstaking implementation of classic and simple public health principles. These measures were instrumental in bringing the global epidemic under control. This chapter examines some of the core principles of public health as they apply to the SARS epidemic in Hong Kong. First, we look at the possible origins of SARS, tracing its roots from rural farms to city markets and beyond. Then we dissect the early actions, or lack thereof, of public health authorities in affected areas worldwide and discuss how and why they handled the outbreak differently. The third section deals with the generation of scientific evidence and how it can be and has been usefully employed to control the epidemic. We conclude with a discussion of more generic systems issues, problems and potential solutions for Hong Kong to consider in better preparing itself for the next infectious disease outbreak.