Science 320, 531–535 doi:10.1126/science.1155164 (2008)

The vaccinia virus had a dirty secret. Researchers in Switzerland have revealed that it dupes cells into taking it in by mimicking the detritus that many types of cell would normally mop up.

The work is important because vaccinia typifies pox viruses such as smallpox. Jason Mercer and Ari Helenius of ETH Zurich watched fluorescently labelled virus particles trigger the membranes of their target cells to develop a spherical bulge called a 'bleb'. Blebbing proved crucial for infection, and a fat molecule called phosphatidylserine in the viral membrane proved crucial for virus-induced blebbing. Because the process normally deals with 'rubbish' in healthy cells, it flies under the radar of the immune system and thus enables pox viruses to evade detection as they spread between cells.