ABSTRACT
A total of 730 children aged less than 7 years, attending 8 day-care centers (DCCs) in Belém, Brazil were followed-up from January to December 1997 to investigate the occurrence of human-herpes virus 6 (HHV-6) infection in these institutional settings. Between October and December 1997 there have been outbreaks of a febrile- and -exanthematous disease, affecting at least 15-20 percent of children in each of the DCCs. Both serum- and- plasma samples were obtained from 401 (55 percent) of the 730 participating children for the detection of HHV-6 antibodies by enzyme-linked immunosorbent assay (ELISA), and viral DNA amplification through the nested-PCR. Recent HHV-6 infection was diagnosed in 63.8 percent (256/401) of them, as defined by the presence of both IgM and IgG-specific antibodies (IgM+/IgG+); of these, 114 (44.5 percent) were symptomatic and 142 (55.5 percent) had no symptoms (p = 0.03). A subgroup of 123 (30.7 percent) children were found to be IgM-/IgG+, whereas the remaining 22 (5.5 percent) children had neither IgM nor IgG HHV-6- antibodies (IgM-/IgG-). Of the 118 children reacting strongly IgM-positive ( > or = 30 PANBIO units), 26 (22.0 percent) were found to harbour the HHV-6 DNA, as demonstrated by nested-PCR. Taken the ELISA-IgM- and- nested PCR-positive results together, HHV-6 infection was shown to have occurred in 5 of the 8 DCCs under follow-up. Serological evidence of recent infections by Epstein-Barr virus (EBV) and parvovirus B19 were identified in 2.0 percent (8/401) and 1.5 percent (6/401) of the children, respectively. Our data provide strong evidence that HHV-6 is a common cause of outbreaks of febrile/exanthematous diseases among children attending DCCs in the Belém area
Subject(s)
Humans , Male , Female , Infant , Child, Preschool , Child , Child Day Care Centers , Disease Outbreaks , Exanthema Subitum/epidemiology , Herpesvirus 6, Human/isolation & purification , Antibodies, Viral/blood , Brazil/epidemiology , DNA, Viral , Enzyme-Linked Immunosorbent Assay , Exanthema Subitum/blood , Exanthema Subitum/diagnosis , Follow-Up Studies , Herpesvirus 6, Human/immunology , Immunoglobulin G/blood , Immunoglobulin M/blood , Polymerase Chain Reaction , Urban PopulationABSTRACT
Sera from healthy donors and patients stored over a period of 2 years, aged 1 to 83 years, were examined for reactivity to human herpes virus 6 (HHV-6) by the standard indirect immunofluorescence assay (IFA). Of the 600 serum specimens screened, 502 showed positive reactivity to HHV-6. This gives an overall seropositive rate of 83.7%. There is no significant difference in the overall positive rate between the ethnic groups (Chinese, Malays, Indians) (chi 2 = 0.35 df = 2 p > 0.05). However, there is significant difference in the positive rates at the extreme age groups of 1 year as well as 61 years and above. From birth up to below 1 year of age, the seroprevalence rate was 82%. At one year of age the positive rate decreased to 66% before gradually rising so that the percentage seropositivity of 6 to 10 years old becomes similar to that in older children and adults (11 to 40 years). The positive rate then starts to decline after 40 years of age. Using a standardized scoring system, the corresponding antibody titer was found to be high in the very young population and starts to decline after the age of 15 years. This suggests that in our population group, primary infection occurs mainly in the pediatric age group. It also accounts for the low positive rate in the age group of 61 years and above, as by then the titer had fallen to the level below the detection limits of the assay system.