Methods: This research examined how word usage in web blogs (in particular anxiety, health, death and positive emotion words) differed between blogs that mentioned "swine flu" and control blogs published between April 24 and May 7, 2007. Web-based information-seeking behaviour was examined using the pattern of visits to H1N1-related Wikipedia pages from two weeks before to two weeks after the outbreak was announced. The relationship between information seeking and anxiety word use in web blogs was also investigated. Results: Blogs mentioning "swine flu" contained significantly higher levels of anxiety, health and death-related words, and lower levels of positive emotion words that control blogs. Use of anxiety words decreased steadily over the two week study period following the announcement of the H1N1 outbreak. The peak in Wikipedia visits to H1N1-related pages was three days after the peak in anxiety word use measured in web blogs. Lagged Pearson's correlations between language use and daily webpage visits three days later showed significant positive correlations between page views and use of anxiety words in web blogs (r=.76, p<.01).