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Abstract
Objectives: To assess the secondary attack rates (SAR) and impact of the 2009 H1N1 epidemic in Melbourne, Victoria, Australia, and the measures implemented to control household transmission. Methods: Patients with polymerase chain reaction-confirmed influenza A and pandemic H1N1 (pH1N1) were identified from hospital and microbiology laboratory records and asked to take part in a retrospective survey. Information obtained included: the constellation of symptoms, contact history, secondary infection, and household information, including adherence and attitudes towards quarantine measures. Results: The overall SAR of pH1N1 index patients was 30.6%, but a significantly lower SAR was noted with oseltamivir treatment (36.6% vs 22.8%, p < 0.05). The greatest reduction in SAR was observed when index patients aged 0–4 y received oseltamivir (83.3% vs 22.2%, p < 0.01). Quarantine was requested of 65.8% of patients and 92.8% self-reported adhering to recommendations. pH1N1 index patients, the number of median days bed-bound is 2.5 days, being unable or too sick to work for a median of 5.0 days, and lost a median of 7.0 days of work for reasons related to an influenza-like illness. Conclusions: The pH1N1 influenza pandemic had a significant clinical impact on households. Public health interventions such as oseltamivir treatment of index cases were beneficial in reducing secondary attack rates, whilst quarantine measures were found to have high rates of self-reported compliance, understanding, and acceptability.
Declaration of interest: This project was funded by an Australian Commonwealth Government National Health and Medical Research Council (NHMRC) Strategic Award. Conflicting interests: AC is an investigator on a study to examine the adverse events of influenza vaccine, funded by CSL Ltd, the manufacturer of the vaccine. AC has not received any direct funding from any pharmaceutical company and was supported by an NHMRC training fellowship.