Australia Canada 1 Digital public health surveillance 1 Infodemiology 1 Machine learning 1 Online health information 1 Physical activity 1 Political structures: democracy 1 Public administration 1 Public health database 1 Sedentary behavior 1 Sleep 1 Social media analysis 1 United Kingdom 1 United States 1 article 1 controlled study 1 demographics 1 evergreen 1 female 1 gender 1 human 1 infodemiology 1 machine learning 1 male 1 medical information 1 metadata 1 natural language processing 1 nonhuman 1 ontology 1