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

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