15. The bird flu, also known as influenza A, is caused by a virus. Pneumonia, which can have similar symptoms to
influenza A, is caused by a bacterial infection. Which statement best summarizes the difference between these two
diseases?
O Viruses are living organisms while bacteria are not.
O Viruses are non-living organisms while bacteria are living.
O Bacterial infections are harmless to humans while viruses can be deadly.
Bacterial infections are harmful to humans while viruses can be beneficial.