Study: Media can distort public's views on infectious diseases

Nov 5, 2008 (CIDRAP News) – Media coverage of infectious diseases such as avian influenza can create the impression that the conditions are more of a threat than they really are, according to a recent study from Canada.

However, media stories that include factual information on disease symptoms, mortality, and infection rates leave readers with a more accurate view of the risks, according to the authors, who published their findings in the Oct 29 issue of Public Library of Science One (PLoS One). The study group is from McMaster University in Hamilton, Ont.

Meredith Young, lead author and graduate student in McMasters' Department of Psychology, Neuroscience, and Behavior, said in a university press release that the media focus on rare and dramatic events. "When a certain disease receives repeated coverage in the press, people tend to focus on it and perceive it as a real threat," she said. "This raises concerns regarding how people view their own health, how they truly understand disease, and how they treat themselves."

Looking for readership trends
The researchers compared reader impressions of 10 infectious diseases. Five have frequently appeared in the print media—anthrax, severe acute respiratory syndrome (SARS), West Nile virus, Lyme disease, and avian influenza. The other five are rarely mentioned in news stories—tularemia, human babesiosis, yellow fever, Lassa fever, and hantavirus.

In two different experiments, undergraduate psychology students and then medical students were asked to rate the seriousness of the diseases; judge the likelihood that each condition was actually a disease, ie, how "disease like" it was; and estimate how many of their peers would contract the disease in the ensuing year.

To assess if immediately available information can skew perceptions of well-known diseases, the authors randomly assigned some volunteers in each group to make judgments based only on the disease name and others to base their assessments on the disease name followed by a short description. They included a medical student group to assess if the disease perceptions were more accurate in a better informed group.

Frequency skews severity impressions
Both the undergraduates and the medical students rated the "high media frequency" diseases as more serious than the "low media frequency" diseases and gave similar ratings for disease-like status. However, the medical students estimated lower prevalence rates for the diseases.

The disease descriptions tempered the media effect in the undergraduates, but not in the medical students, the authors found. They said a possible reason for this difference is that the medical students may have already had more knowledge about the diseases.

In a third experiment, the authors paired similar disorders—for example, human babesiosis and Lyme disease—based on label-free disease descriptions and asked 12 graduate students to rate severity. These students rated the low-media-frequency diseases as worse than the more heavily covered conditions.

The results suggest that disorders more likely to be covered by the media are not considered to be objectively worse, the authors reported.

The group concluded, on the basis of the three experiments, that repetitive media coverage can bias the public's perceptions of diseases.

"The media function as a critical interface between the scientific community, government, and the public, with a responsibility to strike a careful balance between raising awareness of issues of public concern and irrationally alarming the public at large," they wrote.

Expert weighs in on media coverage
Peter Sandman, PhD, a risk communication expert based in Princeton, N.J., told CIDRAP News that the findings are familiar and stretch beyond infectious diseases. "You find that public concern and media coverage are strongly correlated with each other and that neither is strongly correlated with technical seriousness," he said.

However, Sandman questioned the group's assertion that the media alone influence the level of concern and suggested that the decision to cover a topic is more complex and dynamic. He pointed out that journalists typically cover issues their readers and viewers consider important. "Public concern influences the amount of coverage, the amount of coverage influences public concern, and both are influenced by other characteristics of the disease or risk in question," Sandman said.

Placing a priority on novel diseases can be useful, because sometimes rare and dramatic occurrences are sentinel events, he said. "SARS at first looked like every virologist's worst fears come true. It took a while to learn that super-spreaders were rare and the disease was susceptible to traditional epidemiologic measures."

Other aspects besides seriousness are relevant to a disease's newsworthiness, such as the bioterrorism potential in anthrax and the pandemic risk posed by avian influenza, Sandman said.

"Note also that newsworthy diseases often break policy ground that affects a society's preparedness for less newsworthy diseases as well," he said. "Anthrax, for example, has had a big impact on bioterrorism preparedness policy—which certainly includes preparedness for a tularemia attack."

Sandman said the bottom line is that the media gravitate toward new diseases that have unsettled policy implications and might lead to a natural or manmade disaster.

Early media emphasis on a new infectious disease, before many people die, can help society take early, appropriate precautions, he said. "Sometimes the media miss these potentially serious risks until they become serious in the here-and-now, but sometimes they do their job right," Sandman added.

With avian influenza, the media problem isn't that people have an inflated impression of its risk, he said. "It (media coverage) has died down too quickly, and avian flu hasn't been hooked clearly enough to the pandemic threat."

Young ME, Norman GR, Humphreys KR. Medicine in the popular press: the influence of media on perceptions of disease. PLoS One 2008 Oct 29;3(10):[Full text]

See also:

Oct 29 McMaster University press release

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