During an influenza pandemic, a substantial proportion of transmission is thought to occur in households. Goldstein, et al. (2010) used data on influenza progression in individuals and their contacts collected by the city of Milwaukee Health Department (MHD) to study the transmission of pandemic influenza A/H1N1 virus in 362 households in Milwaukee, Wis., and the effects of oseltamivir treatment and chemoprophylaxis. The research was published in BMC Infectious Diseases.
The researchers report that 135 households had chronological information on symptoms and oseltamivir usage for all household members. The effect of oseltamivir treatment and other factors on the household secondary attack rate was estimated using univariate and multivariate logistic regression with households as the unit of analysis. The effect of oseltamivir treatment and other factors on the individual secondary attack rate was estimated using univariate and multivariate logistic regression with individual household contacts as the unit of analysis, and a generalized estimating equations approach was used to fit the model to allow for clustering within households.
They report that oseltamivir index treatment on onset day or the following day (early treatment) was associated with a 42 percent reduction (OR: 0.58, 95 percent CI: 0.19, 1.73) in the odds of one or more secondary infections in a household and a 50 percent reduction (OR: 0.5, 95 percent CI: 0.17, 1.46) in the odds of a secondary infection in individual contacts. The confidence bounds are wide due to a small sample of households with early oseltamivir index usage -- in 29 such households, five had a secondary attack. Younger household contacts were at higher risk of infection (OR: 2.79, 95 percent CI: 1.50-5.20).
Early oseltamivir treatment may be beneficial in preventing H1N1pdm influenza transmission; this may have relevance to future control measures for influenza pandemics. Larger randomized trials are needed to confirm this finding statistically.
Reference: Goldstein E, Cowling BJ, O'Hagan JJ, Danon L, Fang VJ, Hagy A, Miller JC, Reshef D, Robins J, Biedrzycki P and Lipsitch M. Oseltamivir for treatment and prevention of pandemic influenza A/H1N1 virus infection in households, Milwaukee, 2009. BMC Infectious Diseases 2010, 10:211doi:10.1186/1471-2334-10-211