Seroepidemiology and risk factors for sporadic norovirus/Mexico strain.

Risk factors associated with transmission of sporadic norovirus (NV; formerly Norwalk-like virus)/Mexico strain were identified in a seroepidemiological study conducted in rural Mexico. Acquisition of Mexico strain IgA antibodies was age-related; 34% of 1-4-year-olds were seropositive, compared with 81% of adults (P<.001). After 12 months, 42% of 1-4-year-olds showed a seroresponse to Mexico strain, compared with 27% of adults (P<.01). Personal and domestic hygiene measures, such as hand washing, general cleanliness of the mother's clothing, and the type of room assigned for cooking were significantly associated with odds of a seroresponse. For infants, having a dog in or near the home was a risk factor for seroresponse (P<.01), whereas, for older children, the mother's involvement in agricultural activities was a risk factor (P<.001). This study provides initial evidence of risk factors associated with sporadic NV infection. Data indicate some similarities to risk factors associated with outbreaks of NV infection.