Friday, March 26, 2010

Findings, Gaps, and Future Direction for Research in Nonpharmaceutical Interventions for Pandemic Influenza

During March 4–6, 2009, principal investigators from eleven CDC funded studies met to share results, identify research gaps, and define future research needs to identify, improve, and evaluate the effectiveness of nonpharmaceutical interventions (NPIs) to mitigate the spread of pandemic influenza within communities and across international borders.

At the conference, the researchers expressed that NPI behaviors can be successfully taught to and adopted by a variety of persons through community health education, interactive classroom teaching, or Internet-based instruction. Urban Hispanics had misunderstandings about influenza (e.g., 88% thought that influenza was caused by bacteria), and their knowledge, attitudes, and practices improved through a community education program. Acceptability of NPIs also depends on early planning, consistent and targeted communication during implementation, and clear delineation of responsibilities and authority. Acceptability further requires communication from traditional (i.e., emergency response organizations) and nontraditional (i.e., churches) sources.

Behaviors perceived as typical daily behavior were more readily accepted than nontypical daily behaviors. Hand sanitizing with alcohol-based preparations, washing with soap, covering sneezes and coughs, and being aware of one's hands (e.g., touching face) showed relatively high compliance. Only 1 of 5 projects had good adherence to face mask use, which is not a typical behavior. In addition, efficacy of face masks for preventing transmission of influenza viruses has yet to be fully determined.

NPIs can be efficacious for reducing rates of influenza and influenza-like illness (ILI) in community settings. Household secondary attack ratios were substantially reduced if all household members practiced frequent hand washing and wore face masks within 36 hours after symptom onset in the index patient. University students had a 50%–65% reduced rate of ILI over a 6-week intervention period, using hand hygiene and masks. Mask use was substantial (4–5 hours per day average), which was attributed to adoption of masks as a daily behavior, rather than as a response to illness. Elementary school students using a 5-layered NPI approach, including hand hygiene and cough etiquette, had 53% fewer laboratory-confirmed influenza A infections and 26% fewer total absences compared with a control group.

Household crowding (measured as a deficit of >2 bedrooms) can be a factor in community influenza transmission, significantly increasing the relative risk (RR) for hospitalization for pneumonia or influenza (RR = 1.20, 95% CI 1.05–1.37; age standardized). The mean serial interval (i.e., the time between successive cases of infectious diseases in the chain of transmission) was 3.6 days, based on pairs of persons in 14 households.

School dismissal is part of CDC's pandemic planning, but dismissed students may congregate elsewhere. The number of social contacts by children dropped 67% (p<0.05)>

Rapid, large-scale risk-based entry screening of air travelers for ILI that used questionnaires and health assessments was conducted successfully at 2 airports for 177 flights. Seventy-five percent of passengers who provided contact details were followed up, but few of those with symptoms were prepared to go to a laboratory for collection of a respiratory specimen. On the basis of preliminary analysis, investigators concluded that voluntary travel restrictions would sufficiently protect only isolated populations with low numbers of visitors.

Meeting participants concluded that evidence exists of the effectiveness of NPIs, including face masks, hand hygiene, cough etiquette, reduced crowding, and school closures, in reducing the spread of influenza. Insufficient sample sizes, exacerbated by a mild influenza season during the first funding year, underreporting of disease, and challenges faced by influenza surveillance limited the statistical power of most studies. Further studies with larger sample sizes, common methods to allow pooling of data, and study durations that cover multiple influenza seasons are needed to address these limitations. In addition, studies using engineering controls, such as upper-room ultraviolet C lighting, in populations with naturally acquired infection are needed to address the relative contribution of transmission modalities, e.g., small vs. large respiratory droplets and contact transmission.

Source: CDC Emerging Infectious Diseases

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