The correlation between viral load and quantitative proinflammatory factors profile was analyzed by Pearson's correlation test using Instat software (Vision 5.0, GraphPad prism). Differences were considered significant at p,0.05. Figure S1 The distribution of viral load in selected tissue samples. The viral HA gene and b-actin gene copies in tissues were determined by quantified real-time RT-PCR. The ratios between HA and b-actin gene copies which was showed by logarithm presented the viral-load level in different tissue. Found at: doi:10.1371/journal.pone.0013315.s001 (0.11 MB TIF)  Situational Awareness and Health Protective Responses to Pandemic Influenza A (H1N1) in Hong Kong: A Cross-Sectional Study BACKGROUND: Whether information sources influence health protective behaviours during influenza pandemics or other emerging infectious disease epidemics is uncertain. METHODOLOGY: Data from cross-sectional telephone interviews of 1,001 Hong Kong adults in June, 2009 were tested against theory and data-derived hypothesized associations between trust in (formal/informal) information, understanding, self-efficacy, perceived susceptibility and worry, and hand hygiene and social distancing using Structural Equation Modelling with multigroup comparisons. PRINCIPAL FINDINGS: Trust in formal (government/media) information about influenza was associated with greater reported understanding of A/H1N1 cause (β = 0.36) and A/H1N1 prevention self-efficacy (β = 0.25), which in turn were associated with more hand hygiene (β = 0.19 and β = 0.23, respectively). Trust in informal (interpersonal) information was negatively associated with perceived personal A/H1N1 susceptibility (β = −0.21), which was negatively associated with perceived self-efficacy (β = −0.42) but positively associated with influenza worry (β = 0.44). Trust in informal information was positively associated with influenza worry (β = 0.16) which was in turn associated with greater social distancing (β = 0.36). Multigroup comparisons showed gender differences regarding paths from trust in formal information to understanding of A/H1N1 cause, trust in informal information to understanding of A/H1N1 cause, and understanding of A/H1N1 cause to perceived self-efficacy. CONCLUSIONS/SIGNIFICANCE: Trust in government/media information was more strongly associated with greater self-efficacy and handwashing, whereas trust in informal information was strongly associated with perceived health threat and avoidance behaviour. Risk communication should consider the effect of gender differences. Pandemic influenza A/H1N1 has a clinical profile similar to seasonal influenza, despite initially appearing more severe [1] . Respiratory infectious diseases (RIDs) such as influenza are a major public health issue best dealt with by prevention, ideally vaccination. However, in the first six-months or so of a newlyemergent RID epidemic/pandemic vaccines are generally unavailable and non-pharmacological interventions can play a major role in minimizing RID spread [2] [3] [4] . Government health education messages are a major source of information for promoting self-protective practices against RIDs. These preventive messages generally emphasize improved hygiene, face-mask use by infected persons, and social distancing measures, including avoiding crowds during epidemics [5] [6] [7] .