Risk factors for Epstein-Barr virus infection in Thai infants.

To identify the risk factors for Epstein-Barr virus (EBV) infection among infants in Bangkok, Thailand, a case-control study was conducted during 1997-1999. Blood samples were collected from 257 Thai infants aged 6 months to 2 years. Serum samples were assayed for specific EBV IgG antibodies based on a commercial enzyme-linked immunosorbent assay kit. The subjects' parents were interviewed with structured questionnaires to collect details about their infants' age, sex, socioeconomic background, and place of child rearing. The infants were classified into two groups: positive and negative EBV IgG; factors related to the risks of infection were also determined. The overall seropositivity rate of the study infants was 36.2%. Infants aged 1-2 years had a 3.64 times higher risk than those aged 6 months -1 year (p < 0.0001). Infants living in families with an income of < or = 10,000 baht/month (1 US dollar = 42 baht) had a 1.33 times higher risk than those with a family income of >10,000 baht/month (p = 0.03). Infants who were reared at home had a 2.92 times higher risk than those reared outside the home (p = 0.05). By logistic regression analysis, age (> 1 years) and family income (< or = 10,000 baht/month) were the two risk factors associated with EBV infection.