Analysis of the effectiveness of interventions used during the 2009 A/H1N1 influenza pandemic
Authored by George J Milne, Nilimesh Halder, Joel K Kelso
Date Published: 2010
DOI: 10.1186/1471-2458-10-168
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Abstract
Background: Following the emergence of the A/H1N1 2009 influenza
pandemic, public health interventions were activated to lessen its
potential impact. Computer modelling and simulation can be used to
determine the potential effectiveness of the social distancing and
antiviral drug therapy interventions that were used at the early stages
of the pandemic, providing guidance to public health policy makers as to
intervention strategies in future pandemics involving a highly
pathogenic influenza strain.
Methods: An individual-based model of a real community with a population
of approximately 30,000 was used to determine the impact of alternative
interventions strategies, including those used in the initial stages of
the 2009 pandemic. Different interventions, namely school closure and
antiviral strategies, were simulated in isolation and in combination to
form different plausible scenarios. We simulated epidemics with
reproduction numbers R(0)of 1.5, which aligns with estimates in the
range 1.4-1.6 determined from the initial outbreak in Mexico.
Results: School closure of 1 week was determined to have minimal effect
on reducing overall illness attack rate. Antiviral drug treatment of
50\% of symptomatic cases reduced the attack rate by 6.5\%, from an
unmitigated rate of 32.5\% to 26\%. Treatment of diagnosed individuals
combined with additional household prophylaxis reduced the final attack
rate to 19\%. Further extension of prophylaxis to close contacts (in
schools and workplaces) further reduced the overall attack rate to 13\%
and reduced the peak daily illness rate from 120 to 22 per 10,000
individuals. We determined the size of antiviral stockpile required; the
ratio of the required number of antiviral courses to population was 13\%
for the treatment-only strategy, 25\% for treatment and household
prophylaxis and 40\% for treatment, household and extended prophylaxis.
Additional simulations suggest that coupling school closure with the
antiviral strategies further reduces epidemic impact.
Conclusions: These results suggest that the aggressive use of antiviral
drugs together with extended school closure may substantially slow the
rate of influenza epidemic development. These strategies are more
rigorous than those actually used during the early stages of the
relatively mild 2009 pandemic, and are appropriate for future pandemics
that have high morbidity and mortality rates.
Tags
epidemics
Design
Infection
Model
transmission
Strategies
United-states
Mitigation
School closure
Prophylaxis