News coverage of public health issues: the role of news sources and the processes of news construction.

IntroductionConcerns over public health issues have risen considerably as epidemics (such as SARS, West Nile virus, avian flu and H1N1) and personal health problems (such as cancer and diabetes) have attracted increasing attention both from the mass media and from the general public in the last century (1). To the extent that media coverage of complex subject matters often constitutes the most important source of information for lay audiences (2), understanding how news stories about these subjects are constructed is, therefore, a critical step in the assessment of possible public reactions toward issues such as emerging epidemics or new technologies.An important approach to investigating the news construction process is through the examination of news sources. Previous studies have recognized the critical role of news sources in providing context, explanation, and comments for journalists (4-5). The reliance of journalists on sources is particularly exacerbated in complex areas, such as health-related issues, in which a significant amount of specific technical expertise is required (4), and media coverage tends to reflect the perspectives of vocal spokespersons (6).Research on the use of sources in relation to public health issues has mainly focused on the analysis of the distribution of different source categories or on how journalists decide which source to use (7-9). Rarely does research compare the sourcing patterns across different public health issues, although it has been demonstrated that the pattern of source use varied by issues (4). Comparison of media coverage across diseases could help determine whether journalists account for the specifics of each disease or cover the diseases similarly based on professional values and organizational constraints (2,8-9). By using West Nile virus and avian flu as case studies, this study addresses this gap.West Nile virus and avian fluSince it was first isolated in the West Nile province of Uganda in 1937, West Nile virus outbreaks have occurred in portions of Africa, Southern Europe, North America, and Asia. In the U.S., the first human cases of West Nile encephalitis were recorded in 1999. The Centers for Disease Control and Prevention's (CDC) surveillance of West Nile virus had reported more than 4,000 cases of human infections by the end of 2002. Surveillance programs and precautionary measures such as chemical spraying have been effective in curbing major outbreaks of West Nile virus. However, because increased infections are normally detected in the summer or early fall, West Nile virus has been permanently established as a seasonal epidemic in North America (15).Avian flu, on the other hand, is a more recent epidemic threat. Since the beginning of the outbreak in 2003, 387 human cases, with 245 fatalities, have been confirmed (16). Although the World Health Organization (WHO) considers the highly pathogenic H5N1 avian influenza virus to be mainly dangerous to birds, a pandemic among humans is feared to begin should human-to-human infections ever occur. In the United States, this threat has been viewed to be very serious as evident by President Bush's $7.1 billion plan to prepare for the possibility of a flu pandemic.Both epidemic hazards have originated outside the United States and both have potential for a major pandemic. Although avian flu is currently considered the bigger threat, a West Nile virus outbreak has actually occurred in the United States, making it more of a local issue. In 2007, 3,630 human cases, with 124 fatalities were recorded (17). As evident from the number of reported human cases, West Nile virus has affected a large number of U.S. citizens. In contrast, avian flu can be viewed as mainly an international health risk issue.In addition, these two diseases have generated different types of media attention, with West Nile virus having been confirmed as a seasonal disease and being periodically reported in the news, whereas avian flu is still considered a current issue in the media. …