flu covid-19 virus.coronavirus covid-19 outbreak influenza background.

flu covid19 viruscoronavirus outbreak influenza background 3d 2019ncov biohazard biology china chinese concept contagious corona virus coronavirus cough covid danger dangerous disease epidemic fever global health hospital human illness infect infection infectious medical medicine microbiology ncov pandemic pneumonia prevention protection quarantine respiratory sars science sick sickness viral virology wuhan backgroundpandemic risk cell render as