Table 5.

Topic feature extraction analysis of microblog comments about the COVID-19 pandemic at different stages in China from July 2020 to June 2021.

Stage and subject number		Subject content	Keywords extracted by the LDAa model
Phase 1
	T1	New confirmed cases	Pandemic rebound, death, persistence, fear, migration, virus spread, contagion risk, pandemic prevention
	T2	Import from abroad	Disinfect, detect, security, risk level, classification, source control, viral activity, personnel contact
	T3	Asymptomatic infection	Isolation, therapy, monitor, incubation personal, close contacts, medical observe, infectiousness, immunity
	T4	Nucleic acid testing (NAT)	24 hours, region, sampling method, screening, antigen detection, sampling point, information input, detection result
Phase 2
	T5	Cold chain food	Traceability, cheek, disinfect, safety, risk, touch, nucleic acid testing, virus
	T6	COVID-19 vaccine	Clinical trials, safety, side effect, output, validity, develop, price, inoculate
	T7	Pandemic prevention measures	Face mask, health, disinfect, body temperature, nucleic acid testing, immunity, quarantine, vaccine
	T8	Medium or high-risk areas	Cases, asymptomatic infection, spread risk, medical insurance, living necessities, regional control, nucleic acid testing, health monitoring
Phase 3
	T9	Vaccination	Vaccination rate, necessity, population immunity, adverse reactions, antibody, allergy, personal protection, inoculation contraindication
	T10	Cluster infection	Source of infection, chain of transmission, close contacts, gathering activity, nucleic acid testing, pandemic prevention awareness, route of transmission, policy control
	T11	Variant strain	Omicron, Delta, critically patients, panic, contagious, pathogenic, mortality rate, drug resistance
	T12	Close contact	Centralized isolation, medical observation, nucleic acid testing, body temperature, abnormal signs, incubation period, clinical symptoms, movement tracking

^aLDA: latent Dirichlet allocation.