National Geographic : 2010 Jan
3 2 2 3 FLU VIRUS BRING ON THE ENEMY Remaining cells, lacking a gene they don't need, are infected with a virus, such as flu (orange), that would ordinarily kill them all. Yet it fails to kill some. IDENTIFY SURVIVORS If a cell survives the virus, that suggests the virus couldn't reproduce without the protein encoded by the missing gene. A new antiviral drug might target that protein without harming human cells.