Enteroviruses are members of the Picornaviridae family of viruses, which includes poliovirus, coxsackieviruses, echoviruses, and rhinoviruses. Enteroviruses are often detected in the respiratory secretions (mucus, saliva and sputum) and feces of infected people. While historically polio was the most significant enterovirus infection, global vaccination programs against poliovirus have greatly reduced the prevalence of polio. Non-polio enteroviruses have a high mutation rate and there are more than 60 non-polio enteroviruses causing diseases such as the common cold, flaccid paralysis, aseptic meningitis, myocarditis, conjunctivitis, and hand, foot and mouth disease.
According to CDC estimates, there are 10-15 million non-polio enterovirus infections in the US each year, with infection most likely to occur in the summer and fall. While anyone can become infected with non-polio enterovirus, infants, children and teenagers are more likely to become infected and get sick. As a child grows, exposure to non-polio enteroviruses allows their immune system to develop immunity against future infections.
A 2014 outbreak of Human Enterovirus 68 (abbreviated as EV-68, HEV-68, or EV-D68) in the United States has increased interest in enterovirus infections. EV-68 was first isolated in California in 1962. While rare, it has become more prevalent recently, including the most recent US outbreak. As with other enteroviruses, EV-68 causes a respiratory illness primarily in children, as other enteroviruses do, but is unusual in that EV-68 shares epidemiologic and biological features with human rhinoviruses.
Enterovirus infections are generally mild, with people often showing either no symptoms while infected or mild cold-like symptoms. Non-specific illness with a fever is common in enterovirus infections. However, in some cases, enteroviruses can attack the central nervous system and cause paralysis or even death. Children with asthma or anyone with a weakened immune system seem to be more at risk of complications or severe illness.