Reducing the impact of the next influenza pandemic using household-based public health interventions
Background
The outbreak of highly pathogenic H5N1 influenza in domestic poultry and wild birds has
caused global concern over the possible evolution of a novel human strain [1]. If such a strain
emerges, and is not controlled at source [2,3], a pandemic is likely to result. Health policy in
most countries will then be focused on reducing morbidity and mortality.
Methods and Findings
We estimate the expected reduction in primary attack rates for different household-based
interventions using a mathematical model of influenza transmission within and between
households. We show that, for lower transmissibility strains [2,4], the combination of
household-based quarantine, isolation of cases outside the household, and targeted
prophylactic use of anti-virals will be highly effective and likely feasible across a range of
plausible transmission scenarios. For example, for a basic reproductive number (the average
number of people infected by a typically infectious individual in an otherwise susceptible
population) of 1.8, assuming only 50% compliance, this combination could reduce the infection
(symptomatic) attack rate from 74% (49%) to 40% (27%), requiring peak quarantine and
isolation levels of 6.2% and 0.8% of the population, respectively, and an overall anti-viral
stockpile of 3.9 doses per member of the population. Although contact tracing may be
additionally effective, the resources required make it impractical in most scenarios.
Conclusions
National influenza pandemic preparedness plans currently focus on reducing the impact
associated with a constant attack rate, rather than on reducing transmission. Our findings
suggest that the additional benefits and resource requirements of household-based
interventions in reducing average levels of transmission should also be considered, even
when expected levels of compliance are only moderate.