The prevalence of varicella-zoster virus infection in normal healthy individuals aged above 6 months.

The prevalence of varicella-zoster virus (VZV) infection was studied by determining the presence of IgG antibody to VZV (anti-VZV IgG) using ELISA method. Three hundred and fifty sera collected from Thai healthy individuals aged above 6 months (mean age +/- standard deviation = 14.9 +/- 11.4) were tested, the prevalence of VZV infection was 64.6% (225/350). All samples were randomly sampling from healthy children and blood donors who visited the hospital and clssified into 7 groups, 50 samples each, according to their age, i.e., group 1; 6 months-3 years, group 2; 4-6 years, group 3; 7-9 years, group 4; 10-14 years, group 5; 15-19 years, group 6; 20-24 years and group 7; above 25 years. The prevalence of VZV infection were 12%, 42%, 64%, 70%, 78%, 84% and 100% respectively. The mean amount of anti-VZV IgG among groups of positive VZV infection (225 samples) was 86.8 +/- 29.7 unit/ml. The mean amount of anti-VZV IgG was highest in 6 months-3 years age group (113.6 +/- 39.2 unit/ml). Significant difference of the mean amount of anti- VZV IgG was found between group 1, 3, 6 and other groups (p-value < 0.05). There was a correlation between history of varicella and the presence of anti-VZV IgG in the serum. 95.3% of individuals with positive history has already had the antibody. The important associated factors that might involve VZV infection were age, number of members in family and place of exposure to VZV infection. Other factors, such as sex and income did not show any association to VZV infection.

Seroprevalence of anti-RSV IgG in Thai children aged 6 months to 5 years.

Respiratory syncytial virus (RSV) is the single most important cause of lower respiratory tract infection during infancy and early childhood worldwide including Thailand. The magnitude as well as the intensity of both infection and host response to the RSV infection determine the severity of disease. To determine the presence of anti-RSV IgG in children of different age groups, 124 serum samples were randomly collected from healthy children aged 6 months to 5 years. All of them were assayed for anti-RSV IgG using a commercial ELISA kit. The mean prevalence rate was found to be 68.91%. The prevalence increased with age: from 6 to 11 months, 11.76%; from 12 to 17 months, 41.67%; from 18 to 23 months, 60.87%; from 24 to 29 months, 88.24%; from 30 to 35 months, 78.57%; from 36 to 41 months, 94.44% and from 42 to 60 months, 100%. The amount of anti-RSV IgG among the groups was significantly different (p = 0.006). No sexual preponderance was found. RSV infection commonly occurred in children aged 12 to 29 months. All children older than 5 years had experienced a RSV infection.

Prevalence of parvovirus B19 infection in Thai young adults.

The prevalence of antibody to human parvovirus B19 in 128 Thai healthy young adults was measured. Antibodies of the immunoglobulin G (IgG) class were investigated in serum samples of 51 males and 77 females aged 18-24 years (mean 19.83; SD 1.07) by a commercial enzyme-linked immunosorbent assay (ELISA) using high specific recombinant parvovirus B 19 antigen. Only 14 out of 128 (10.94%) sera were found positive, including 6 males and 8 females. No sex preponderance was observed. The amount of antibody calculated as antibody index was not statistically significant difference between genders.