In the study, researchers "combined a strain of the deadly H5N1 avian virus with strains of H3N2 human seasonal flu, creating 254 new, mutated viruses. By injecting them in lab mice, researchers found that some of the hybrid viruses were both deadly (like bird flu) and transmissible (like seasonal human flu) - the kind of genetically mutated superflu viruses that experts have been warning about for decades," TIME writes. Though "H5N1 has not yet mutated into a more contagious form, despite having had plenty of chances to mix with human flu viruses the PNAS study suggests that the potential exists," and hints at what health officials should be looking for in H5N1 to tip off the virus is becoming more contagious (Walsh, 2/22).

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