Recently a number of children in California have developed a poliomyelitis-like paralysis. The cause of this paralysis is not yet known, and information about the outbreak is scarce. However, acute-flaccid paralysis is not uncommon (California would be expected to report about 75 cases a year, based on its population). The virus that has been isolated from some of the children, enterovirus 68, is mainly known to cause respiratory infections and is not likely the cause. Here are my thoughts on the situation.