NEW YORK All forms of viral hepatitis can be considered emerging diseases, according to Harold S. Margolis, MD, who spoke here at the Ninth Annual Infectious Diseases in Children Symposium.
"I think for the pediatric community, we've clearly merged into an area of beginning to deal with these infectious agents and primarily dealing with some of the prevention issues," said Margolis, chief of the hepatitis branch and director of the WHO Collaborating Center on Research and Reference in Viral Hepatitis at the Centers for Disease Control and Prevention (CDC).
Being able to make the correct hepatitis virus diagnosis is the most important issue for the pediatric community, Margolis said. Each of the hepatitis viruses are different agents. They are not related to each other virologically, and the only thing they have in common is that they predominantly reproduce in the liver. Hepatitis A and hepatitis E are enterically transmitted, primarily being shed in the feces, and neither of them cause chronic infection. However, hepatitis B, C and the delta virus are parenterally transmitted and all cause persistent infection and chronic liver disease.
One of the problems in correctly diagnosing the disease, according to Margolis, is that for children, particularly those younger than 5 years old, most infections are asymptomatic. "Symptoms cannot differentiate each of the diseases," he said. "You really have to go to diagnostic testing."
What practitioners need for diagnosing acute disease are the IgM tests IgM anti-HAV, IgM anti-HBc.
Vaccination is the best way to prevent hepatitis A virus (HAV). Both of the vaccines available are killed-virus vaccines and are highly immunogenic. Most people seroconvert after the first dose with the second dose acting as a booster. The vaccines have efficacies of 96% to 100%. Passive immunization still remains in place, using immunoglobulin, for contacts of cases and during common source outbreaks.
Most HAV disease in the United States occurs in community-wide outbreaks, and children play an important role in disease transmission. Margolis cited the polio vaccine experience as a model for immunizing with HAV vaccine: there was widespread catch-up immunization, followed by routine infant immunization once the polio disease rates had been lowered. Although HAV vaccine is not routinely recommended for children today, Margolis predicted that as the future for HAV immunization.
For controlling and preventing hepatitis B virus (HBV), the issues are the case management of infants born to surface antigen positive mothers and the vaccinations of infants, high-risk children and adolescents. Since the HBV vaccine was added to the routine immunization schedule in 1992, 60% of children receive all three doses. In comparison, 90% of children receive three doses of Haemophilus influenzae type b (Hib) vaccine. This is an increase from the early days of Hib vaccination, however. Two to four years after Hib vaccine was added to the schedule, there was only 70% coverage. Margolis expects HBV vaccine rates to increase similarly.
It is important for pediatricians to vaccinate children of immigrants, who have emigrated from countries where there is a high rate of hepatitis. This includes children of Asian-born parents, of which there are 1.4 million in the United States, between the ages of 1 and 10.
The infection rate in these children is 8% to to 15%, compared with less than 1% in non-Asian children. Pediatricians should vaccinate these infants and make an effort to play "catch-up" to immunize older siblings.
This "catch-up" strategy was used to immunize Alaska Natives, who have a high rate of HBV. There are no chronically infected children in the 10-year immunized cohort, and the rate of asymptomatic and essentially insignificant infections is less than 1%.
There are 22,000 infants born to HBsAg mothers annually. Only about 89% receive HBIG vaccine at birth and about 67% receive three-dose vaccination by 6 months of age. Verification of HBsAG testing on birth certificates helps to remind the perinatal practitioner in the hospital and, therefore, increases the vaccination rate, Margolis said. But it is up to the office practitioner to continue the schedule.
Other members of that baby's household also need to be vaccinated. Data show that in households of an antigen-positive woman about 70% of her other children are also susceptible.
Hepatitis B vaccination should also be routine for adolescents. Thirty percent of young gay men between the ages of 17 and 22 have serologic evidence of HBV infection. "At that age that prevalence is no different than what we saw in terms of risk of HBV infection among young gay men in the 1970s," Margolis said. "We are not vaccinating high-risk groups, even as high-risk adolescents."
Clinical hepatitis C disease is rarely seen in children or adults, Margolis said. Data from the National Health Nutrition Examination survey shows that 1.8% of the U.S. population is infected with HCV. Children who received blood transfusions prior to 1990 are at risk, he added.
Addressing risk behavior is the other hepatitis C issue. Injection drug users, including adolescents, become rapidly infected with HCV. Reducing high-risk behavior and counseling these adolescents are important.
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