Non-Polio Enterovirus Infections
What are enteroviruses?
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.
How common are infections with these viruses?
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.
Who is at risk of infection and illness from these viruses?
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.
How does someone become infected with one of these viruses?
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.
What time of year is someone at risk for infection/illness?
In the United States, infections caused by the enteroviruses are most likely to occur during the summer and fall.
What illnesses do these viruses cause?
Most people who are infected with an enterovirus have no disease at all. Infected persons who become ill usually develop either mild upper respiratory symptoms (a "summer cold"), a flu-like illness with fever and muscle aches, or an illness with rash. Less commonly, some persons have "aseptic" or viral meningitis. Rarely, a person may develop an illness that affects the heart (myocarditis) or the brain (encephalitis) or causes paralysis. Enterovirus infections are suspected to play a role in the development of juvenile-onset diabetes mellitus (sugar diabetes). Newborns infected with an enterovirus may rarely develop severe illness and die from infection.
Are there any long-term complications from these illnesses?
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.
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 by pregnant women may help to decrease the risk of infection during pregnancy and around the time of delivery.
What are the health care costs of these infections?
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.
Are these infections more severe in some years than in others?
There are no predictable patterns of circulation of these viruses or of diseases such as "aseptic" meningitis. There are occasional national or regional outbreaks of "aseptic" meningitis, such as the echovirus 30 outbreaks in the United States between 1989 and 1992 and in 2003, and echovirus 13 and echovirus 18 outbreaks in 2001. However, there is significant yearly variation, and no long-term trends have been identified.
Can these infections be prevented?
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. 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.