Risk factors and patterns of household clusters of respiratory viruses in rural Nepal

Scott, E. M.; Magaret, A.; Kuypers, J.; Tielsch, J. M.; Katz, J.; Khatry, S. K.; Stewart, L.; Shrestha, L.; LeClerq, S. C.; Englund, J. A.; Chu, H. Y.

This prospective household surveillance study was nested within a randomised controlled trial designed to determine the effectiveness of influenza vaccine during pregnancy [16, 17] . The study site is in the low-lying region of rural southern Nepal called the 'terai', with inhabitants broadly representative of the population of India, Bangladesh and Nepal [18] . All women of childbearing age in a part of one district were surveyed for pregnancy. Pregnant women were enrolled in the primary trial as early as possible in pregnancy, generally during the second trimester, and followed until 6 months postpartum. At the time of randomisation, every third study mother and their families were selected to participate in a household surveillance substudy. As randomisation occurred at the time of vaccination, not initial enrolment, randomisation occurred after enrolment and the start of surveillance for some mothers. Surveillance for the first participant enrolled in the household substudy began on 14 April 2011 and we included the households of substudy mothers enrolled prior to 1 May 2012. Surveillance of the household ended 180 days after birth. In this area, many households consist of multiple families living in a single compound; households were defined as a group sharing a single cookstove. Socio-demographic data were collected upon enrolment at the individual and household levels. Birth assessments of study infants were performed shortly following birth. Infants weighed within 72 h of the birth were considered to be low birthweight if the infant weighed <2.5 kg.