Exposure rate of VZV among women attending antenatal care clinic in Sri Lanka - a cross sectional study

BACKGROUND Varicella or chickenpox was not a notifiable disease until 2005 in Sri Lanka and only a few studies have been conducted on the epidemiology of VZV infection in the country. The anti-VZV IgG sero-prevalence among antenatal women is extremely limited and thus a selected group of antenatal clinic attendees were chosen to determine the exposure rate to VZV infection. METHODS Women attending the antenatal clinic at Teaching Hospital, Peradeniya, Sri Lanka were selected for the study and 3 mL of venous blood was collected from 181 participants and the demographic data was obtained through a pre-tested questionnaire. Sera of the women were then tested for the presence of anti-VZV IgG using ELISA (HUMAN Diagnostics, Germany). Data was analysed using the SPSS statistical software for Windows, Version 12.0. RESULTS Of the 181 antenatal women who took part in the study, 141 were positive for anti-VZV IgG giving a sero-prevalence of 77.9% for the past exposure to VZV. Of the 141 anti-VZV IgG positive women, 43.3% (n = 61) were from urban, 41.8% (n = 59) were from rural and 14.9% (n = 21) were from estate populations (an ethnic population living in small settlements in the tea estates whose ancestors were brought from India during the British colonial period to work in the tea plantations in Sri Lanka). Out of the 88 antenatal women with a positive history for varicella, 85 (96.6%) were positive for anti-VZV IgG. The highest number of anti-VZV IgG positivity was seen in the 31-35 age group, which was 85.0% of the total number of antenatal women included in that category. An increase in the anti-VZV IgG sero-prevalence with increasing age was also noted in the study sample. CONCLUSION Exposure rate of VZV infection as confirmed by anti-VZV IgG in the present study sample of antenatal women was 77.9%. Age specific, population based future sero-prevalence studies should be conducted in Sri Lanka to understand the anti-VZV IgG status in the country.