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Flu Pandemic Could Be Stopped With Early Actions
Aug. 4, 2005 - A carefully chosen combination of
public health measures, if implemented early, could stop the spread of
an avian flu outbreak at its source, suggest two international teams of
researchers in Nature
(August 3) and Science
(August 5). This deadly virus poses the potential threat of the flu
pandemic that could kill thousands of people, with senior citizens being
the most vulnerable.
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Related Story |
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Pandemic Flu Projection Says More Than Half Million
Could Die in U.S.
Chart shows expected deaths, hospitalization, cases
by state
June 24, 2005 - Trust for America's Health (TFAH)
today released state-by-state projections that found over half a million
Americans could die and over 2.3 million could be hospitalized if a
moderately severe strain of a pandemic flu virus hits the U.S. Senior
citizens and the elderly would be at high risk. Based on the model
estimates, 66.9 million Americans are at risk of contracting the
disease. Read more...see
state chart
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The researchers used computer modeling to simulate
what might happen if avian flu were to start passing efficiently between
people in Southeast Asia. They found that antiviral treatment is a
critical component of any multi-pronged approach.
The computer simulations are part of the Models of
Infectious Disease Agent Study (MIDAS) research network funded by the
National Institute of General Medical Sciences (NIGMS), a component of
the National Institutes of Health. The overall goal is to develop
computational models of disease spread that will aid the development of
effective control strategies.
These new models illustrate how the fundamental
features of infectious disease spread can be captured to predict
possible outcomes and the potential impact of interventions, said
Jeremy M. Berg, Ph.D., director of NIGMS. As these modeling approaches
develop, they will offer policymakers and researchers powerful tools to
use in strategic planning.
The H5N1 strain of the avian flu virus, found in birds throughout
Southeast Asia, has infected a number of species, including domestic
poultry, pigs, and people. Scientists fear that a genetic exchange
between bird and human flu viruses or the accumulation of H5N1 mutations
could soon make efficient person-to-person transmission possible.
The avian flu strain represents a particular threat
because it is so deadly, said Neil M. Ferguson, D.Phil., a computational
biologist at Imperial College in London and lead author of the
Nature paper. A large
percentage of animals and people infected with this virus have died, he
explained. The consequences of an H5N1-based pandemic could be
catastrophic.
With bird flu continuing to spread in Southeast
Asia, the MIDAS network decided to model a hypothetical human outbreak
of H5N1 in this region.
The pressing questions are if and how we can
contain an outbreak of avian flu at the source before it becomes a
pandemic, said Ira M. Longini, Jr., Ph.D., a biostatistician at the
Emory University Rollins School of Public Health in Atlanta and lead
author of the Science
paper.
To enhance reliability, both models were based on
detailed data for Thailand, such as population densities, household
sizes, age distribution, and distances traveled to work. The models also
included information about the flu virus, such as the possible
contagiousness of an infected person. Ferguson and Longini noted that
actual contagiousness would not be known before an outbreak.
Although the models differed in the specific
scenarios they simulated and the intervention strategies they tested,
the general conclusions were similar and confirm current knowledge of
how diseases spread: Preventing a pandemic would require a combination
of carefully implemented public health measures introduced soon after
the first cases appear.
The model presented in
Nature simulated 85 million
people living in Thailand and bordering regions of neighboring
countries. It tested the effectiveness of giving courses of antiviral
treatment to everyone, socially or geographically targeting who received
them, and combining these drug-sparing approaches with other
interventions, such as restricting travel.
The results suggest that an international stockpile
of 3 million courses of flu antiviral drugs, combined with other
interventions, could contain a pandemic. Treating infected individuals
and everyone in their vicinity, along with closing schools and
workplaces, could have more than a 90 percent chance of stopping the
spread of a pandemic virus, according to the model. Ferguson emphasized
that successful containment would depend on the early detection of the
first cases and the rapid implementation of public health measures.
The model described in
Science simulated 500,000
people living in rural Southeast Asia and relied on information about
how those individuals move within their communities. Containment
strategies included giving antiviral medication to people in the same
social networks, vaccinating before an outbreak with a vaccine that is
not well matched to the strain that emerges, quarantining the houses or
neighborhoods of infected people, and combinations of these approaches.
Giving a low-efficacy vaccine to just half the
population before the start of a pandemic would greatly enhance the
success of other containment strategies, according to the model. Longini
reported that a combination of targeted antiviral treatment and
quarantine introduced two weeks after the first case had the potential
to successfully contain disease spread, resulting in less than one case
per 1,000 people.
Both models demonstrated that the need for
additional public health measures greatly increased as the virus became
more contagious. Each measure can have a significant effect, but it
cant contain spread on its own, said Ferguson, adding that targeted
antiviral treatment was a crucial component of all combined strategies.
While the researchers said that implementing such a
combination of approaches would be challenging and require a
coordinated, international response, they offered this good news: The
models show that containing an avian flu pandemic at its source is
feasible.
Because computer models cannot capture all the
complexities of real communities and real outbreaks, the MIDAS
researchers will continue to refine their simulations and test different
scenarios as new information becomes available. By developing a
collection of models, they can compare and contrast different
interventions, leading to more accurate predictions.
Other researchers involved in this work represent
Johns Hopkins Bloomberg School of Public Health; the University of Hong
Kong; the Ministry of Health in Thailand; and INSERM, the French
National Institute of Health and Medical Research.
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This is a
snapshot taken about 60 to 90 days after the first case of an
uncontrolled outbreak of transmissible avian flu in people
living in Thailand. Red indicates new cases while green
indicates areas where the epidemic has finished.
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The accompanying movie (available for download at
http://www.nigms.nih.gov/news/releases/videos/ferguson_video_1.ram)
shows the spread of infection and recovery over 300 days in Thailand and
neighboring countries (click to download Free
RealPlayer). Both graphics are reproduced from supplementary
information on this work published in
Nature and are courtesy of
Neil M. Ferguson of Imperial College in London.
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This is a
snapshot taken partway through a controlled outbreak of
transmissible avian flu in people living in Thailand. Red
indicates areas of infection while blue indicates areas where a
combination of control measures has been implemented. |
The accompanying movie (available for download at
http://www.nigms.nih.gov/news/releases/videos/ferguson_video_2.ram)
shows that this approach contains the infection in 90 days, before it
spreads elsewhere (click to download Free
RealPlayer). Both graphics are reproduced from supplementary
information on this work published in
Nature and are courtesy of
Neil M. Ferguson of Imperial College in London.
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