Transmission Electron Micrograph (TEM) depicting a number of virions found responsible for a case of acute hemorrhagic conjunctivitis (AHC). Acute hemorrhagic conjunctivitis (AHC) is a rapidly progressive, and highly contagious viral disease that is primarily caused by 2 distinct enteroviruses: enterovirus 70 (EV70) and a variant of coxsackievirus A24 (CA24v). Enteroviruses are a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Serologic studies have distinguished 71 human enterovirus serotypes on the basis of antibody neutralization tests. Enteroviruses were originally classified into four groups, polioviruses, Coxsackie A viruses (CA), Coxsackie B viruses (CB), and echoviruses, but it was quickly realized that there were significant overlaps in the biological properties of viruses in the different groups. Enteroviruses isolated more recently are named with a system of consecutive numbers: EV68, EV69, EV70, EV71, etc. There are 64 non-polio enteroviruses that can cause disease in humans: 23 Coxsackie A viruses, 6 Coxsackie B viruses, 28 echoviruses, and 5 other enteroviruses. Magnification: unknown.