Household transmission of seasonal influenza from HIV-infected and HIV-uninfected individuals in South Africa, 2013-2014

Abstract

BACKGROUND : We estimated the household secondary infection risk (SIR) and serial interval (SI) for influenza transmission from HIV-infected and HIV-uninfected index cases. METHODS : Index cases were the first symptomatic person in a household with influenza-like illness, testing influenza positive on real-time reverse transcription polymerase chain reaction (rRT-PCR). Nasopharyngeal swabs collected from household contacts every 4 days were tested by rRT-PCR. Factors associated with SIR were evaluated using logistic regression. RESULTS : We enrolled 28 HIV-infected and 57 HIV-uninfected index cases. On multivariable analysis, HIV-infected index cases were less likely to transmit influenza to household contacts (odds ratio [OR] 0.2; 95% confidence interval [CI], 0.1–0.6; SIR 16%, 18/113 vs 27%, 59/220). Factors associated with increased SIR included index age group 1–4 years (OR 3.6; 95% CI, 1.2–11.3) and 25–44 years (OR 8.0; 95% CI, 1.8–36.7), and contact age group 1–4 years (OR 3.5; 95% CI, 1.2–10.3) compared to 5–14 years, and sleeping with index case (OR 2.7; 95% CI, 1.3–5.5). HIV infection of index case was not associated with SI. CONCLUSIONS : HIV-infection was not associated with SI. Increased infectiousness of HIV-infected individuals is likely not an important driver of community influenza transmission.