Coloured transmission electron micrograph (TEM) of cytomegalovirus (CMV) particles (purple) in intracellular vesicles in an infected macrophage (immune cell, blue). Cytomegaloviruses are a genus of double-stranded DNA (dsDNA) viruses which infect humans and monkeys. CMV infection is a common chronic infection affecting people of all ages. It is symptomless in most cases, but can cause flu-like symptoms upon initial infection. It can be passed to babies before birth (congenital CMV), in which case more serious symptoms can occur, including a rash, yellowing of the skin and eyes (jaundice), low birth weight, a smaller head than usual (microcephaly), seizures and problems with the eyes, ears, liver and spleen. CMV typically self-resolves, though antivirals are sometimes used to treat babies.