Non-Polio enterovirus infections

Epidemiology and Demographics
Non-polio enteroviruses are very common. They are second only to the "common cold" viruses, the rhinoviruses, as the most common viral infectious agents in humans. The enteroviruses cause an estimated 10-15 million or more symptomatic infections a year in the United States. All three types of polioviruses have been eliminated from the Western Hemisphere, as well as Western Pacific and European regions, by the widespread use of vaccines.

Enteroviruses can be found in the respiratory secretions (e.g., saliva, sputum, or nasal mucus) and stool of an infected person. Other persons may become infected by direct contact with secretions from an infected person or by contact with contaminated surfaces or objects, such as a drinking glass or telephone. Parents, teachers, and child care center workers may also become infected by contamination of the hands with stool from an infected infant or toddler during diaper changes.

Risk Factors
Everyone is at risk of infection. Infants, children, and adolescents are more likely to be susceptible to infection and illness from these viruses, because they are less likely to have antibodies and be immune from previous exposures to them, but adults can also become infected and ill if they do not have immunity to a specific enterovirus.

What are the risks of enterovirus infections in pregnancy?

Because enteroviruses are very common, pregnant women are frequently exposed to them, especially during summer and fall months. As for any other adults, the risk of infection is higher for pregnant women who do not have antibodies from earlier exposures to enteroviruses currently circulating in the community, and are exposed to young children - the primary spreaders of these viruses.

Most enterovirus infections during pregnancy cause mild or no illness in the mother. Although the available information is limited, currently there is no clear evidence that maternal enteroviral infection causes adverse outcomes of pregnancy such as abortion, stillbirth, or congenital defects. However, mothers infected shortly before delivery, may pass the virus to the newborn. Babies born to mothers who have symptoms of enteroviral illness around the time of delivery are more likely to be infected. Newborns infected with an enterovirus usually have mild illness, but rarely they may develop an overwhelming infection of many organs, including liver and heart, and die from the infection. The risk of this severe illness is higher for the newborns infected during the first two weeks of life.

Strict adherence to generally recommended good hygienic practices (see "Can these infections be prevented?" below) by pregnant women may help to decrease the risk of infection during pregnancy and around the time of delivery.

Pathophysiology & Etiology
Enteroviruses are small viruses that are made of ribonucleic acid (RNA) and protein. This group includes the polioviruses, coxsackieviruses, echoviruses, and other enteroviruses. In addition to the three different polioviruses, there are 62 non-polio enteroviruses that can cause disease in humans: 23 Coxsackie A viruses, 6 Coxsackie B viruses, 28 echoviruses, and 5 other enteroviruses.

Risk Stratification and Prognosis
Usually, there are no long-term complications from the mild illnesses or from "aseptic" meningitis. Some patients who have paralysis or encephalitis, however, do not fully recover. Persons who develop heart failure (dilated cardiomyopathy) from myocarditis require long-term care for their conditions.

Primary Prevention
No vaccine is currently available for the non-polio enteroviruses. Because most persons who are infected with enteroviruses do not become sick, it can be difficult to prevent the spread of the virus. General cleanliness and frequent handwashing are probably effective in reducing the spread of these viruses (see "Handwashing" in: An Ounce of Prevention: Keeps the Germs Away). Also, cleaning contaminated surfaces and soiled articles first with soap and water, and then disinfecting them with a dilute solution of chlorine-containing bleach (made by mixing approximately ¼ cup of bleach with 1 gallon of water) can be a very effective way to inactivate the virus, especially in institutional settings such as child care centers. (See more about cleaning and disinfecting in general in CDC's Prevention Resources).

Cost-Effectiveness of Therapy
The health care costs from enterovirus infections are unknown, but a large portion of the costs may come from use of over-the-counter medications to treat symptoms for millions of cases of "summer colds" and "flu" caused by enteroviruses. There are also significant costs associated with the 25,000 to 50,000 hospitalizations for "aseptic" meningitis each year in the United States.

Acknowledgements
The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.