Why are respiratory infections so common?

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    Many are caused by viruses, which are difficult to control by using antibiotics.
     For many, the biology of the pathogen makes development of a vaccine difficult.
     Some can be spread by a person before he/she begins exhibiting symptoms.
     All of the above.
     More than one of the above, but not all.
asked May 16, 2012 in Microbiology by anonymous
    

1 Answer

0 votes
All of the above.
answered May 17, 2012 by Bioshare ~Top Expert~ (34,070 points)



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