Rotaviruses are the most common cause of severe diarrhea and kill hundreds of thousands of infants a year. Although current vaccines are effective in preventing aggravation of rotaviruses, the development of more effective vaccines at lower cost is expected. Technology cannot study well how rotaviruses invade and replicate in a cell. To identify which genes are crucial for the infection of rotaviruses, scientists at the Research Institute for Microbial Diseases at Osaka University report a new plasmid-based reverse genetics system. The study can be read in Proceedings of the National Academy of Sciences of the United States of America.