Human adenovirus strain J.J. subtype D/10 (HAdV-10). Scanning electron micrograph (SEM) of a human alveolar basal epithelial cell (A549 cell line) incubated with HAdV-10 for 1-2 hours. The image shows the first stage of infection where an uninfected cell has 100nm diameter non-enveloped virus particles (blue) bound to receptors on the plasma membrane prior to the virus being internalised into the cell. Adenoviruses are a group of viruses that can cause mild to severe infection throughout the body. Adenovirus infections most commonly affect the respiratory system, eyes, and the gastrointestinal tract. These infections can cause symptoms similar to the common cold and flu or pneumonia, conjunctivitis, or acute gastroenteritis. Most adenovirus infections are mild. Magnification: x 6000 when printed 10 centimetres wide. Specimen courtesy of Virology Research Services Ltd (Scott Lawrence).