Influenza epidemics, caused by influenza A or B viruses, result in acute respiratory infection. They kill half a million people worldwide every year. These viruses can also wreak havoc on animals, as in the case of avian flu. A team has now identified how the influenza A virus manages to penetrate cells to infect them. By attaching itself to a receptor on the cell surface, it hijacks the iron transport mechanism to start its infection cycle. By blocking the receptor involved, the researchers were also able to significantly reduce its ability to invade cells. These results highlight a vulnerability that could be exploited to combat the virus.