LAUSR

BACKGROUND Social media not only provide platforms for the public to obtain information about a disease but also allow them to share their opinions and experiences about it. METHODS This study analyzed 3000 tweets systematically selected from over 1 million tweets posted during the 2015 California measles outbreak. RESULTS News updates were the most tweeted messages (41.4%), followed by personal opinions (33.7%), resources (19.4%), personal experiences (2.5%), and questions (1.6%). Susceptibility was the most discussed health belief (21.8%), followed by cues to action (18.9%) and severity (13.0%). Individuals were significantly more likely to discuss severity. Nonprofit organizations were significantly more likely to offer cues to action than other user types, and media were less likely to include cues to action than other user types. Pro-vaccine tweets were more likely to contain links to traditional mainstream media sources such as newspapers and magazines, and anti-vaccine tweets were more likely to link to emerging news websites. CONCLUSIONS Understanding who posts what on social media during an infectious disease outbreak allows public health agencies to better assess the public's attitudes, sentiments, and needs in order to provide timely and effective information.