“Swine flu” strain has passed from humans to swine nearly 400 times since 2009 (IMAGE)
Caption
Dr. Giovana Ciacci Zanella swabbing a pig snout to gather samples to test for influenza A virus
Credit
M.Marti and A.Grimes, USDA (CC-BY 2.0, https://creativecommons.org/licenses/by/2.0/
Usage Restrictions
Credit must be given to the creator.
License
CC BY