What's this?
influenza
What's this?
swallow
What's this?
mucus
What's this?
microscope
What's this?
scrape
What's this?
bacteria
What's this?
virus
What's this?
disease
What's this?
paralyzed
What are these?
cells
What's this?
immune
What's this?
infect
What's this?
Common Cold