Colorized transmission electron micrograph of Marburg virus particles (blue) harvested from infected VERO E6 cell supernatant. Image captured and color-enhanced at the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health, Integrated Research Facility in Fort Detrick, Maryland (USA); the image was retrieved via Flickr and modified by MIC. The cover is published under the Creative Commons Attribution (CC BY) license.