Early assessment of anxiety and behavioral response to novel swine-origin influenza A(H1N1)

Abstract

Background: Since late April, 2009, a novel influenza virus A (H1N1), generally referred to as the "swine flu," has spread around the globe and infected hundreds of thousands of people. During the first few days after the initial outbreak in Mexico, extensive media coverage together with a high degree of uncertainty about the transmissibility and mortality rate associated with the virus caused widespread concern in the population. The spread of an infectious disease can be strongly influenced by behavioral changes (e.g., social distancing) during the early phase of an epidemic, but data on risk perception and behavioral response to a novel virus is usually collected with a substantial delay or after an epidemic has run its course.

Methodology/principal findings: Here, we report the results from an online survey that gathered data (n = 6,249) about risk perception of the Influenza A(H1N1) outbreak during the first few days of widespread media coverage (April 28-May 5, 2009). We find that after an initially high level of concern, levels of anxiety waned along with the perception of the virus as an immediate threat. Overall, our data provide evidence that emotional status mediates behavioral response. Intriguingly, principal component analysis revealed strong clustering of anxiety about swine flu, bird flu and terrorism. All three of these threats receive a great deal of media attention and their fundamental uncertainty is likely to generate an inordinate amount of fear vis-a-vis their actual threat.

Conclusions/significance: Our results suggest that respondents' behavior varies in predictable ways. Of particular interest, we find that affective variables, such as self-reported anxiety over the epidemic, mediate the likelihood that respondents will engage in protective behavior. Understanding how protective behavior such as social distancing varies and the specific factors that mediate it may help with the design of epidemic control strategies.

Figure 1. Frequencies of the categories of respondents' contacts outside the home.

Figure 2. Means for the perceived threat levels for different sources of risk.

Bars show Bonferroni-corrected 95% confidence intervals. Codes: 1 = no risk, 5 = very high risk; “swine” = Novel Swine-Origin Influenza A(H1N1), “diabetes” = Diabetes mellitus, “HIV” = HIV/AIDS, “injury” = Unintentional injury, “terror” = Terrorism, “heart” = Heart Disease, “cancer” = Cancer, “H5N1” = Bird Flu, “H3N2” = Seasonal Flu.

Figure 3. Frequency distribution of personal risk perceptions.

While most respondents rate their personal risk as low, note the pronounced second mode at the intermediate level of risk perception.

Figure 4. Frequency distribution of personal empowerment.

Again, while most respondents list a high level of personal empowerment, there is a decided second mode at the intermediate level (1 = “very high: I feel confident I can avoid infection”, 5 = “intermediate”, 9 = “very low: I feel I will not be able to avoid infection”).

Figure 5. Frequency distribution of the protection measures undertaken by respondents.

(“sneeze” = avoid people sneezing or coughing, “gathering” = avoid large gatherings, “wash” = wash hands more frequently, “shun” = avoid people perceived to be sick and potentially infectious, “public” = avoid public places, “school” = stay home from school or work, “Mexico” = avoid travel to affected foreign countries or states, “disinfectant” = use alcohol-based disinfectant, “mask” = wear a protective mask).

Figure 6. Mean values of sources of information on swine flu cited by respondents.

Bars show Bonferroni-corrected 95% confidence intervals. Codes: 1 = never use as source of information, 5 = very frequently use as a source of information.

Figure 7. Changes in difference between observed and expected values of the protection index over the seven days of the survey.

The pattern is significantly different from the expected pattern based on marginal frequencies (χ² = 113.1, df = 54, p<0.001).

Figure 8. Changes in difference between observed and expected values of the emotional status over the seven days of the survey.

The pattern is significantly different from the expected pattern based on marginal frequencies (χ² = 135.6, df = 48, p<0.001).