Impact of Non-Pharmaceutical Interventions on URIs and Influenza in Crowded, Urban Households

Objectives. We compared the impact of three household interventions-education, education with alcohol-based hand sanitizer, and education with hand sanitizer and face masks-on incidence and secondary transmission of upper respiratory infections (URIs) and influenza, knowledge of transmission of URIs, and vaccination rates. Methods. A total of 509 primarily Hispanic households participated. Participants reported symptoms twice weekly, and nasal swabs were collected from those with an influenza-like illness (ILI). Households were followed for up to 19 months and home visits were made at least every two months. Results. We recorded 5,034 URIs, of which 669 cases reported ILIs and 78 were laboratory-confirmed cases of influenza. Demographic factors significantly associated with infection rates included age, gender, birth location, education, and employment. The Hand Sanitizer group was significantly more likely to report that no household member had symptoms (p<0.01), but there were no significant differences in rates of infection by intervention group in multivariate analyses. Knowledge improved significantly more in the Hand Sanitizer group (p<0.0001). The proportion of households that reported >= 50% of members receiving influenza vaccine increased during the study (p<0.001). Despite the fact that compliance with mask wearing was poor, mask wearing as well as increased crowding, lower education levels of caretakers, and index cases 0-5 years of age (compared with adults) were associated with significantly lower secondary transmission rates (all p<0.02). Conclusions. In this population, there was no detectable additional benefit of hand sanitizer or face masks over targeted education on overall rates of URIs, but mask wearing was associated with reduced secondary transmission and should be encouraged during outbreak situations. During the study period, community concern about methicillin-resistant Staphylococcus aureus was occurring, perhaps contributing to the use of hand sanitizer in the Education control group, and diluting the intervention's measurable impact.