One of the most important issues in any society is attention to health, which is regarded as an indicator of development. Planning in this area should be based on scientific and practical criteria. Health communication is one dimension of health-related issues that focuses on informing and raising public awareness. The transformation of communication, which today is predominantly based on digital communication, has changed the process of health communication and public awareness through health messages, making such messages accessible via news websites and social media. This study examines health-related messages during the one-year period from 2019 to 2020, corresponding to the COVID-19 pandemic, drawing on two sources of information dissemination—news websites and social media—and conducts sentiment and semantic analyses of COVID-19-related two-word expressions (bigrams). The study employed both quantitative and qualitative methods to analyze linguistic data. Accordingly, it relied on the compilation of a linguistic corpus from news websites and social media during the aforementioned period. Following the collection and normalization of the data and the selection of health messages related to COVID-19, high-frequency COVID-19-related bigrams were extracted, and the data were subjected to statistical and linguistic analyses. The findings showed that: (a) as the dissemination of health messages decreased, the mortality rate of the pandemic increased; (b) health messages predominantly conveyed negative sentiment; (c) the intensity of negative sentiment conveyed through health messages was greater on news websites than on social media; (d) social media employed greater lexical diversity to express negative sentiment; and (e) the lexical similarity between the content words used and COVID-19-related keywords indicated that, in health messages published on news websites, specialized terms from the fields of “medical, biological, and health sciences” were more prevalent, whereas on social media, greater semantic similarity was observed among words related to “threat, danger, and negative consequences.” Accordingly, this study suggests that health messages should be disseminated in language capable of counteracting the negative sentiment conveyed by such messages, thereby establishing effective communication with audiences while fostering hope and positive feelings. Furthermore, these messages should be expressed in simple, non-specialized language that can effectively communicate with and engage the audience.