BACKGROUND: Human herpesvirus 6 (HHV6), which was first discovered by Salahuddin in 1986, can be classified as HHV6 A and HHV6 B subgroups. It has been known that HHV6 B, which causes exanthem subitum, is related to the febrile illness of children while HHV6 A can be found in immunodeficiency patients. Over 90% of those who went through primary infection before two years of age show seropositive in adulthood. The virus can be detected in over 85% of the adult saliva. This suggests that the asymptomatic latent virus in normal adult saliva may be a source of primary infection by excretion. The objective of this study is to provide the basic seroepidemiology by finding the age of HHV6 primary infection and the extent of latent infection with classifying subgroups for healthy Korean children. METHODS: Healthy Korean children under the age of fifteen were classified into fifteen groups in total. Those groups under one year old age were divided into twelve groups with the interval of one month while those over one year old age were divided into three groups with the interval of five years. Thirty children were involved in each group, and sex ratio was almostly equal. The specific IgG antibody of HHV6 was evaluated by using an ELISA method. HHV6 DNA extracted from the saliva of the subject of fifty healthy children ranging from ages five to fifteen were detected and classified two subgroups by using a nested PCR. RESULTS: Statistically, the specific IgG antibody, which was highly maintained since neonatal age, became significantly decreased between 4 months and 6 months, and thereafter increased rapidly until it reached a peak for infants between 11 months and 12 months, and maintained a stationary high antibody level and high antibody positive rates (above 85%) until 15 years of age. The HHV6 DNA, detected in 18 (36%) out of 50 normal children between 5 and 15 years old, was totally confirmed as HHV6 B. CONCLUSION: Our data suggest that primary infection of HHV6 for Korean children may be occurred after 6 months age, and primary infection of HHV6 may be almostly happened before 1year age old. And HHV6 is excreted intermittently from the saliva of healthy children as in the case of adults. HHV6 B may be the major cause of HHV6 infection in healthy Korean children.
Adolescent ; Adult ; Child* ; DNA ; Enzyme-Linked Immunosorbent Assay ; Exanthema ; Herpesvirus 6, Human* ; Humans* ; Immunoglobulin G ; Infant ; Polymerase Chain Reaction ; Saliva ; Sex Ratio

BACKGROUND: Although the incidence of hepatitis A infection has dramatically declined in developed countries, it is still endemic in many of developing countries, and sporadic outbreak has developed in many middle classed endemic area. Many reports indicate that hepatitis A vaccine would have to be used for widespread immunization of infants, who live in endemic or non-endemic region, for eliminating this infection from circulation. Therefor, the optimal immunization schedule and dose of vaccine should be determined. Recent several studies suggested that high dose hepatitis A vaccination at the time of disappearance of maternal antibody promise protectable immunogenicity in infants. The purpose of our study to find out the prevalence and persistence of maternal HAV antibodies in Korean infants (below 2 years old age). METHODS: 60 mother without past-history of hepatitis A, and 300 heathy infants without history of hepatitis A vaccination and intra-familial contact history of hepatitis A were enrolled in this study. The infants below 2 years old age were classified into 5 groups as following; 0~3 months, 4~6 months, 7~9 months, 10~12 months, 13~24 months, and the number of each group were 60 and sex distribution of each group was equal. Positive rates of Anti-HAV were determined by ELISA. And comparisons of seroprevalence of anti- HAV between groups were analyzed by ANOVA repeated t-test. RESULTS: The seropositive rate of maternal group was 81.7%, and the seropositive rate of 0~3 months of age group was 43.3%. The seroprevalence of anti- HAV significantly declined after 4~6 months of age, and reached below 10% at the age of 7~9 months of age and the low rate of anti-HAV maintained until 2 years old age. And positive rates of anti-HAV showed no significant differences between males and females. CONCLUSION: The results of our study showed that the seroprevalence of anti-HAV significantly declined after 4~6 months of age and the anti-HAV almostly disappeared at 7~9 months of age. So, low seropositive rate of anti-HAV at 7 months of age may justify trials on infant vaccination in Korea.
Antibodies ; Child, Preschool ; Developed Countries ; Developing Countries ; Enzyme-Linked Immunosorbent Assay ; Female ; Hepatitis A ; Hepatitis A Antibodies ; Hepatitis A Vaccines ; Hepatitis* ; Humans ; Immunization ; Immunization Schedule ; Incidence ; Infant* ; Korea ; Male ; Mothers ; Prevalence* ; Seroepidemiologic Studies ; Sex Distribution ; Vaccination