Forty years after they identified the highly contagious intestinal pathogen norovirus, scientists now have finally learned how the virus infects its hosts and can culture it in the lab (Science 2014, DOI: 10.1126/science.1257147). This advance should greatly hasten the understanding of human norovirus’s workings and may lead to future treatment strategies. Stephanie M. Karst and Melissa K. Jones of the University of Florida and their colleagues hypothesize that the virus attaches itself to histoblood group antigens that dot the surface of the enteral bacteria Enterobacter cloacae. The bacteria cross the human intestinal membrane, taking the virus with them, where the virus can then infect underlying B cells. The group identified the phenomenon when they were able to culture human norovirus present in fecal matter from an infected person—which also contained bacteria—in B cells. Attempts to grow pure virus extracted from the samples failed. This tagalong strategy has been recognized in other viruses, including polio, that also call on intestinal bacteria for help in infecting humans. In addition to facilitating norovirus study, the new work adds to the growing recognition of the importance of microbial communities, and their relationships with viruses, in human biology.