All About Enterovirus

by: ANTHONY MINNEFOR, M.D.

CHAIRMAN, DEPARTMENT OF PEDIATRICS AT SAINT BARNABAS MEDICAL CENTER

The relentless, severe winter of 2002-2003 is finally over. Gone with it is the central role that respiratory tract infections play as a cause of illness in the pediatric population. While a problem throughout the year, respiratory tract infections continue to diminish in relative importance until they re-merge in the fall. Waiting to help fill the "void" is a family of viruses known as the enterovirus.

While there is year to year variability, the enteroviruses are generally an important cause of illness in the spring, summer and fall. The warmer the weather during this period, the more likely it is that enteroviruses will appear on the scene earlier and linger longer in the community. The enterovirus family includes the three poliovirus and 60 or more other viruses that for categorization purposes are simply numbered. These are important viruses. Even though wild-type poliovirus has been essentially eradicated from this continent, the other enteroviruses are responsible for 10-15 million symptomatic infections in the United States each year. Plus, over half of the febrile illnesses in the summer are due to the enteroviruses.

Young Most at Risk

The target population for the enteroviruses for the most part includes infants, adolescents and young adults. The manifestations will often vary depending on the age group affected. The virus is spread from child to child via the fecal-oral and potentially the oral-oral (respiratory) route. Children are usually the means by which the virus is introduced into the family. With increasing age generally comes increased immunity to infection. Accordingly, most "older" individuals are immune.

As noted, young adults do run the risk of developing symptomatic infection. This can become important when pregnant women become infected with an enterovirus (symptomatic or sub-clinical) at or near the time of delivery. Under those circumstances, the newborn infant may show all the signs and symptoms of a bacterial infection. In that situation, it is because the neonate is born without adequate maternal antibody against the causative virus. Another group of patients at risk of severe disease are those immuno-compromised individuals with deficiencies in antibody production (an uncommon situation).

Symptoms and Diagnosis

For the vast majority of individuals infected by enteroviruses the conditions produced are more troublesome than serious. The usual incubation period is 3-6 days. The virus, which is present in stool, respiratory secretions and blood, can even be spread "silently" by patients with sub-clinical illness. Because it is such a common entity, enteroviruses have been conveniently classified as causing a syndrome of "acute undifferentiated fever with or without a rash." This helps to explain the difficulty your pediatrician may encounter with an individual patient. These infections are generally considered a "diagnoses of exclusion" (i.e. if nothing else is a likely cause of the problem). The seasonal appearance of illness, the presence of a community "outbreak," or a rash and its characteristics can all be useful clues to the diagnosis. Diagnostic tests for enterovirus are not generally needed in most instances. Accordingly, the overwhelming majority of patients can and are diagnosed clinically.

The combination of fever with rash can be the most common "syndrome" but will depend on a particular season’s predominant enteroviruses and their propensity to cause rashes. These viruses can be the culprit for tonsillitis, pharyngitis and a condition called herpangina in which there are small painful ulcers in the mouth. When the hands and feet are also involved the condition has been called hand, foot and mouth syndrome. During some years, nausea, vomiting and diarrhea may be present.

Because enterviruses cause viremia (the appearance of a virus in the blood), they can potentially infect any organ. These other conditions are too rare to note here. One exception is aseptic meningitis. This condition is almost always benign. Patients often complain of headache and stiff neck. Special studies in this instance can be submitted in such patients to confirm the enteroviral cause.

Treatment

There is no specific treatment available for enteroviral infection, although active research is underway. These infections might well be considered a rite of passage, since no vaccine is available and none is likely in the foreseeable future. Most cases last several days and are of mild to moderate severity. If severity and/or length of illness are concern, as usual, your pediatrician should be consulted.