Scientists find secret 'back door' flu viruses use to enter cells
![Scientists find secret 'back door' flu viruses use to enter cells](https://cdn.mos.cms.futurecdn.net/zTipaAATgmyWEuAvTQgJbK.jpg)
Flu viruses that can use a second cellular entry point may move more effectively between animals and humans, scientists say.
Flu viruses that can use a second cellular entry point may move more effectively between animals and humans, scientists say.