Influenza pandemic preparedness in France: modelling the impact of interventions

A systematic literature review on public health and healthcare resources for pandemic preparedness planning

BACKGROUND

Generating insights into resource demands during outbreaks is an important aspect of pandemic preparedness. The EU PANDEM-2 project used resource modelling to explore the demand profile for key resources during pandemic scenarios. This review aimed to identify public health and healthcare resources needed to respond to pandemic threats and the ranges of parameter values on the use of these resources for pandemic influenza (including the novel influenza A(H1N1)pdm09 pandemic) and the COVID-19 pandemic, to support modelling activities.

METHODS

We conducted a systematic literature review and searched Embase and Medline databases (1995 - June 2023) for articles that included a model, scenario, or simulation of pandemic resources and/or describe resource parameters, for example personal protective equipment (PPE) usage, length of stay (LoS) in intensive care unit (ICU), or vaccine efficacy. Papers with data on resource parameters from all countries were included.

RESULTS

We identified 2754 articles of which 147 were included in the final review. Forty-six different resource parameters with values related to non-ICU beds (n = 43 articles), ICU beds (n = 57), mechanical ventilation (n = 39), healthcare workers (n = 12), pharmaceuticals (n = 21), PPE (n = 8), vaccines (n = 26), and testing and tracing (n = 19). Differences between resource types related to pandemic influenza and COVID-19 were observed, for example on mechanical ventilation (mostly for COVID-19) and testing & tracing (all for COVID-19).

CONCLUSION

This review provides an overview of public health and healthcare resources with associated parameters in the context of pandemic influenza and the COVID-19 pandemic. Providing insight into the ranges of plausible parameter values on the use of public health and healthcare resources improves the accuracy of results of modelling different scenarios, and thus decision-making by policy makers and hospital planners. This review also highlights a scarcity of published data on important public health resources.

The FLURESP European commission project: cost-effectiveness assessment of ten public health measures against influenza in Italy: is there an interest in COVID-19 pandemic?

BACKGROUND

The FLURESP project is a public health research funded by the European Commission, with the objective to design a methodological framework to assess the cost-effectiveness of existing public health measures against human influenza pandemics. A dataset has been specifically collected in the frame of the Italian health system. As most of interventions against human influenza are relavant against other respiratory diseases pandemics, potential interests in COVID-19 are discussed.

METHODS

Ten public health measures against human influenza pandemics pandemic were selected to be also relevant to other respiratory virus pandemics such as COVID 19: individual (hand washing, using masks), border control (quarantine, fever screening, border closure), community infection (school closure, class dismissal, social distancing, limitation of public transport), reduction of secondary infections (implementation of antibiotic therapy guidelines), pneumococcal vaccination for at-risk people, development of Intensive Care Unit (ICU) capacity, implementation of life support equipments in ICU, screening interventions, vaccination programs targeting health professional and targeting general population.

RESULTS

Using mortality reduction as effectiveness criteria, the most cost-effective strategies are "reduction of secondary infections" and "implementation of life support equipment in ICU". The least cost-effective option whatever the level of pandemic events are screening interventions and mass vaccination.

CONCLUSIONS

A number of intervention strategies against human influenza pandemics appears relevant against every respiratory virus, including the COVID-19 event. Measures against pandemics should be considered according to their expected effectiveness but also their costs for the society because they impose substantial burden to the population, confirming the interest of considering cost-effectiveness of public health measures to enlighten decision making.

Cost-effectiveness of public health interventions against human influenza pandemics in France: a methodological contribution from the FLURESP European Commission project

BACKGROUND

The FLURESP project is a public health project funded by the European Commission with the objective to design a methodological approach in order to compare the cost-effectiveness of existing public health measures against human influenza pandemics in four target countries: France, Italy, Poland and Romania. This article presents the results relevant to the French health system using a data set specifically collected for this purpose.

METHODS

Eighteen public health interventions against human influenza pandemics were selected. Additionally, two public-health criteria were considered: 'achieving mortality reduction ≥40%' and 'achieving morbidity reduction ≥30%'. Costs and effectiveness data sources include existing reports, publications and expert opinions. Cost distributions were taken into account using a uniform distribution, according to the French health system.

RESULTS

Using reduction of mortality as an effectiveness criterion, the most cost-effective options was 'implementation of new equipment of Extracorporeal membrane oxygenation (ECMO) equipment'. Targeting vaccination to health professionals appeared more cost-effective than vaccination programs targeting at risk populations. Concerning antiviral distribution programs, curative programs appeared more cost-effective than preventive programs. Using reduction of morbidity as effectiveness criterion, the most cost-effective option was 'implementation of new equipment ECMO'. Vaccination programs targeting the general population appeared more cost-effective than both vaccination programs of health professionals or at-risk populations. Curative antiviral programs appeared more cost-effective than preventive distribution programs, whatever the pandemic scenario.

CONCLUSION

Intervention strategies against human influenza pandemics impose a substantial economic burden, suggesting a need to develop public-health cost-effectiveness assessments across countries.

Reflecting on prediction strategies for epidemics: Preparedness and public health response

Objective

To provide an overview of the literature on respiratory infectious disease epidemic prediction, preparedness, and response (including pharmaceutical and nonpharmaceutical interventions) and their impact on public health, with a focus on respiratory conditions such as asthma.

Data Sources

Published literature obtained through PubMed database searches.

Study Selections

Studies relevant to infectious epidemics, asthma, modeling approaches, health care access, and data analytics related to intervention strategies.

Results

Prediction, prevention, and response strategies for infectious disease epidemics use extensive data sources and analytics, addressing many areas including testing and early diagnosis, identifying populations at risk of severe outcomes such as hospitalizations or deaths, monitoring and understanding transmission and spread patterns by age group, social interactions geographically and over time, evaluating the effectiveness of pharmaceutical and nonpharmaceutical interventions, and understanding prioritization of and access to treatment or preventive measures (eg, vaccination, masks), given limited resources and system constraints.

Conclusion

Previous epidemics and pandemics have revealed the importance of effective preparedness and response. Further research and implementation need to be performed to emphasize timely and actionable strategies, including for populations with particular health conditions (eg, chronic respiratory diseases) at risk for severe outcomes.

Pandemic Risk Assessment Model (PRAM): a mathematical modeling approach to pandemic influenza planning

The Pandemic Risk Assessment Model (PRAM) is a mathematical model developed to analyse two pandemic influenza control measures available to public health: antiviral treatment and immunization. PRAM is parameterized using surveillance data from Alberta, Canada during pandemic H1N1. Age structure and risk level are incorporated in the compartmental, deterministic model through a contact matrix. The model characterizes pandemic influenza scenarios by transmissibility and severity properties. Simulating a worst-case scenario similar to the 1918 pandemic with immediate stockpile release, antiviral demand is 20·3% of the population. With concurrent, effective and timely immunization strategies, antiviral demand would be significantly less. PRAM will be useful in informing policy decisions such as the size of the Alberta antiviral stockpile and can contribute to other pandemic influenza planning activities and scenario analyses.

A mathematical model of avian influenza with half-saturated incidence

The widespread impact of avian influenza viruses not only poses risks to birds, but also to humans. The viruses spread from birds to humans and from human to human In addition, mutation in the primary strain will increase the infectiousness of avian influenza. We developed a mathematical model of avian influenza for both bird and human populations. The effect of half-saturated incidence on transmission dynamics of the disease is investigated. The half-saturation constants determine the levels at which birds and humans contract avian influenza. To prevent the spread of avian influenza, the associated half-saturation constants must be increased, especially the half-saturation constant H m for humans with mutant strain. The quantity H m plays an essential role in determining the basic reproduction number of this model. Furthermore, by decreasing the rate β m at which human-to-human mutant influenza is contracted, an outbreak can be controlled more effectively. To combat the outbreak, we propose both pharmaceutical (vaccination) and non-pharmaceutical (personal protection and isolation) control methods to reduce the transmission of avian influenza. Vaccination and personal protection will decrease β m, while isolation will increase H m. Numerical simulations demonstrate that all proposed control strategies will lead to disease eradication; however, if we only employ vaccination, it will require slightly longer to eradicate the disease than only applying non-pharmaceutical or a combination of pharmaceutical and non-pharmaceutical control methods. In conclusion, it is important to adopt a combination of control methods to fight an avian influenza outbreak.

Was mandatory quarantine necessary in China for controlling the 2009 H1N1 pandemic?

The Chinese government enforced mandatory quarantine for 60 days (from 10 May to 8 July 2009) as a preventative strategy to control the spread of the 2009 H1N1 pandemic. Such a prevention strategy was stricter than other non-pharmaceutical interventions that were carried out in many other countries. We evaluated the effectiveness of the mandatory quarantine and provide suggestions for interventions against possible future influenza pandemics. We selected one city, Beijing, as the analysis target. We reviewed the epidemiologic dynamics of the 2009 H1N1 pandemic and the implementation of quarantine measures in Beijing. The infectious population was simulated under two scenarios (quarantined and not quarantined) using a deterministic Susceptible-Exposed-Infectious-Recovered (SEIR) model. The basic reproduction number R0 was adjusted to match the epidemic wave in Beijing. We found that mandatory quarantine served to postpone the spread of the 2009 H1N1 pandemic in Beijing by one and a half months. If mandatory quarantine was not enforced in Beijing, the infectious population could have reached 1,553 by 21 October, i.e., 5.6 times higher than the observed number. When the cost of quarantine is taken into account, mandatory quarantine was not an economically effective intervention approach against the 2009 H1N1 pandemic. We suggest adopting mitigation methods for an influenza pandemic with low mortality and morbidity.

Systematic review of economic evaluations of preparedness strategies and interventions against influenza pandemics

BACKGROUND

Although public health guidelines have implications for resource allocation, these issues were not explicitly considered in previous WHO pandemic preparedness and response guidance. In order to ensure a thorough and informed revision of this guidance following the H1N1 2009 pandemic, a systematic review of published and unpublished economic evaluations of preparedness strategies and interventions against influenza pandemics was conducted.

METHODS

The search was performed in September 2011 using 10 electronic databases, 2 internet search engines, reference list screening, cited reference searching, and direct communication with relevant authors. Full and partial economic evaluations considering both costs and outcomes were included. Conversely, reviews, editorials, and studies on economic impact or complications were excluded. Studies were selected by 2 independent reviewers.

RESULTS

44 studies were included. Although most complied with the cost effectiveness guidelines, the quality of evidence was limited. However, the data sources used were of higher quality in economic evaluations conducted after the 2009 H1N1 pandemic. Vaccination and drug regimens were varied. Pharmaceutical plus non-pharmaceutical interventions are relatively cost effective in comparison to vaccines and/or antivirals alone. Pharmaceutical interventions vary from cost saving to high cost effectiveness ratios. According to ceiling thresholds (Gross National Income per capita), the reduction of non-essential contacts and the use of pharmaceutical prophylaxis plus the closure of schools are amongst the cost effective strategies for all countries. However, quarantine for household contacts is not cost effective even for low and middle income countries.

CONCLUSION

The available evidence is generally inconclusive regarding the cost effectiveness of preparedness strategies and interventions against influenza pandemics. Studies on their effectiveness and cost effectiveness should be readily implemented in forthcoming events that also involve the developing world. Guidelines for assessing the impact of disease and interventions should be drawn up to facilitate these studies.

Estimates of the impact of a future influenza pandemic in China

Background  The next influenza pandemic will create a surge in demand for health resources in China, with its current population of >1·3 billion persons and under‐developed medical care and public health system. However, few pandemic impact data are available for China.

Objectives  We estimated the effects of a future influenza pandemic in China by examining pandemic scenarios of varying severity and described the time distribution of cases during a first wave.

Methods  We used a Monte‐Carlo simulation model and death rates, hospitalizations and outpatient visits for 1918‐ and 1968‐like pandemic scenarios and data from the literature or experts’ opinion to estimate four health outcomes: deaths, hospitalizations, outpatient medical visits and clinical illness for which medical care was not sought. For each of the two scenarios we estimated outcomes by week using a normal distribution.

Results  We estimated that a 1968 scenario in China would result in 460 000–700 000 deaths, 1·94–2·27 million hospitalizations, 111–117 million outpatient visits and 192–197 million illnesses for which medical care was not sought. Fifty‐two percent of hospitalizations occurred during the two‐peak weeks of the first wave. We estimated that patients at high‐risk of influenza complications (10–17% of the population) would account for 61–75% of all deaths. For a 1918 scenario, we estimated that 4·95–6·95 million deaths, 20·8–22·7 million hospitalizations and 101–108 million outpatient visits could occur.

Conclusion  Even a 1968 pandemic scenario will pose substantial challenges for the medical and public health system in China, and planning to manage these challenges is essential.

Optimizing tactics for use of the U.S. antiviral strategic national stockpile for pandemic influenza

In 2009, public health agencies across the globe worked to mitigate the impact of the swine-origin influenza A (pH1N1) virus. These efforts included intensified surveillance, social distancing, hygiene measures, and the targeted use of antiviral medications to prevent infection (prophylaxis). In addition, aggressive antiviral treatment was recommended for certain patient subgroups to reduce the severity and duration of symptoms. To assist States and other localities meet these needs, the U.S. Government distributed a quarter of the antiviral medications in the Strategic National Stockpile within weeks of the pandemic's start. However, there are no quantitative models guiding the geo-temporal distribution of the remainder of the Stockpile in relation to pandemic spread or severity. We present a tactical optimization model for distributing this stockpile for treatment of infected cases during the early stages of a pandemic like 2009 pH1N1, prior to the wide availability of a strain-specific vaccine. Our optimization method efficiently searches large sets of intervention strategies applied to a stochastic network model of pandemic influenza transmission within and among U.S. cities. The resulting optimized strategies depend on the transmissability of the virus and postulated rates of antiviral uptake and wastage (through misallocation or loss). Our results suggest that an aggressive community-based antiviral treatment strategy involving early, widespread, pro-rata distribution of antivirals to States can contribute to slowing the transmission of mildly transmissible strains, like pH1N1. For more highly transmissible strains, outcomes of antiviral use are more heavily impacted by choice of distribution intervals, quantities per shipment, and timing of shipments in relation to pandemic spread. This study supports previous modeling results suggesting that appropriate antiviral treatment may be an effective mitigation strategy during the early stages of future influenza pandemics, increasing the need for systematic efforts to optimize distribution strategies and provide tactical guidance for public health policy-makers.

Paediatric pandemic planning: children's perspectives and recommendations

Children, as major stakeholders in paediatric hospitals, have remained absent from discussions on important healthcare issues. One critical area where children's voices have been minimised is in the planning for future pandemics. This paper presents a subset of data from a programme of research which examined various stakeholder experiences of the severe acute respiratory syndrome (SARS) outbreaks of 2003. These data also generated recommendations for future pandemic planning. Specifically, this paper will examine the perspectives and recommendations of children hospitalised during SARS in a large paediatric hospital in Canada. Twenty-one (n = 21) child and adolescent participants were interviewed from a variety of medical areas including cardiac (n = 2), critical care (n = 2), organ transplant (n = 4), respiratory medicine (n = 8) and infectious diseases (patients diagnosed with suspected or probable SARS; n = 5). Data analyses exposed a range of children's experiences associated with the outbreaks as well as recommendations for future pandemic planning. Key recommendations included specific policies and guidelines concerning psychosocial care, infection control, communication strategies and the management of various resources. This paper is guided by a conceptual framework comprised of theories from child development and literature on children's rights. The authors call for greater youth participation in healthcare decision-making and pandemic planning.

Preparing your intensive care unit for the second wave of H1N1 and future surges

Faced with increased demands for critical care services as a result of the novel H1N1 pandemic, hospitals must prepare a surge response in an attempt to manage these needs. In preparing for a surge response, factors to consider are staff, stuff (supplies and equipment), space, and systems necessary to respond to the event. This article uses this general framework to discuss surge issues in the context of H1N1 challenges that we are facing currently and to provide specific advice for hospitals. Particular attention is given to how hospitals can estimate the potential impact of H1N1 and pharmaceutical stockpiling.

Mitigation of pandemic influenza: review of cost-effectiveness studies

We conducted a review of economic evaluations of pandemic influenza control measures. In the studies found, we detected various interventions being investigated: antiviral stockpiling and treatment, prophylaxis, vaccination, school closure and restricting international travel. Cost-effectiveness varied but often showed potentials for the favorable economic profiles of these measures. Both static and dynamic models were used. We conclude that the choice of an appropriate model - in particular, a dynamic model - is crucial to arrive at valid cost-effectiveness ratios. Yet, of the economic evaluations considered here, only a few were based on dynamic modeling. We recommend that further research is directed toward linking dynamic epidemiological models for pandemic spread with economic outcomes by considering the full impacts on national economies, including direct, indirect, medical and nonmedical costs.

Optimal resource allocation model to mitigate the impact of pandemic influenza: a case study for Turkey

Pandemic influenza has been considered as a serious international health risk by many health authorities in the world. In mitigating pandemic influenza, effective allocation of limited health resources also plays a critical role along with effective use of medical prevention and treatment procedures. A national resource allocation program for prevention and treatment must be supported with the right allocation decisions for all regions and population risk groups. In this study, we develop a multi-objective mathematical programming model for optimal resource allocation decisions in a country where a serious risk of pandemic influenza may exist. These resources include monetary budget for antivirals and preventive vaccinations, intensive care unit (ICU) beds, ventilators, and non-intensive care unit (non-ICU) beds. The mathematical model has three objectives: minimization of number of deaths, number of cases and total morbidity days during a pandemic influenza. This model can be used as a decision support tool by decision makers to assess the impact of different scenarios such as attack rates, hospitalization and death ratios. These factors are found to be very influential on the allocation of the total budget among preventive vaccination, antiviral treatment and fixed resources. The data set collected from various sources for Turkey is used and analyzed in detail as a case study.

Optimizing tactics for use of the U.S. Antiviral Strategic National Stockpile for Pandemic (H1N1) Influenza, 2009

Public health agencies across the globe are working to mitigate the impact of the 2009 pandemic caused by swine-origin influenza A (H1N1) virus. Prior to the large-scale distribution of an effective vaccine, the primary modes of control have included careful surveillance, social distancing and hygiene measures, strategic school closures, other community measures, and the prudent use of antiviral medications to prevent infection (prophylaxis) or reduce the severity and duration of symptoms (treatment). Here, we use mathematical models to determine the optimal geo-temporal tactics for distributing the U.S. strategic national stockpile of antivirals for treatment of infected cases during the early stages of a pandemic, prior to the wide availability of vaccines.We present a versatile optimization method for efficiently searching large sets of public health intervention strategies, and apply it to evaluating tactics for distributing antiviral medications from the U.S. Strategic National Stockpile (SNS). We implemented the algorithm on a network model of H1N1 transmission within and among U.S. cities to project the epidemiological impacts of antiviral stockpile distribution schedules and priorities. The resulting optimized strategies critically depend on the rates of antiviral uptake and wastage (through misallocation or loss). And while a surprisingly simple pro rata distribution schedule is competitive with the optimized strategies across a wide range of uptake and wastage, other equally simple policies perform poorly.Even as vaccination campaigns get underway worldwide, antiviral medications continue to play a critical in reducing H1N1-associated morbidity and mortality. If efforts are made to increase the fraction of cases treated promptly with antivirals above current levels, our model suggests that optimal use of the antiviral component of the Strategic National Stockpile may appreciably slow the transmission of H1N1 during fall 2009, thereby improving the impact of targeted vaccination. A more aggressive optimized antiviral strategy of this type may prove critical to mitigating future flu pandemics, but may increase the risk of antiviral resistance.

How to deal with partially analyzable acts?

In some situations, a decision is best represented by an incompletely analyzed act: conditionally on a given event A, the consequences of the decision on sub-events are perfectly known and uncertainty becomes probabilizable, whereas the plausibility of this event itself remains vague and the decision outcome on the complementary event is imprecisely known. In this framework, we study an axiomatic decision model and prove a representation theorem. Resulting decision criteria aggregate partial evaluations consisting of (i) the conditional expected utility associated with the analyzed part of the decision, and (ii) the best and worst consequences of its non-analyzed part. The representation theorem is consistent with a wide variety of decision criteria, which allows for expressing various degrees of knowledge on () and various types of attitude toward ambiguity and uncertainty. This diversity is taken into account by specific models already existing in the literature. We exploit this fact and propose some particular forms of our model incorporating these models as sub-models and moreover expressing various types of beliefs concerning the relative plausibility of the analyzed and the non-analyzed events ranging from probabilities to complete ignorance that include capacities.

Epidemic patch models applied to pandemic influenza: contact matrix, stochasticity, robustness of predictions

Due to the recent emergence of H5N1 virus, the modelling of pandemic influenza has become a relevant issue. Here we present an SEIR model formulated to simulate a possible outbreak in Italy, analysing its structure and, more generally, the effect of including specific details into a model. These details regard population heterogeneities, such as age and spatial distribution, as well as stochasticity, that regulates the epidemic dynamics when the number of infectives is low. We discuss and motivate the specific modelling choices made when building the model and investigate how the model details influence the predicted dynamics. Our analysis may help in deciding which elements of complexity are worth including in the design of a deterministic model for pandemic influenza, in a balance between, on the one hand, keeping the model computationally efficient and the number of parameters low and, on the other hand, maintaining the necessary realistic features.

[Contribution of simulation models to public health decisions: the influenza pandemic]

The influenza pandemic threat had led to an increased awareness and several countries have used models to assess the impact of control measures on the influenza pandemic. We reviewed the publications related to simulation models since 2003 and discuss their contribution to public health decision in France. The studies conclude that rapid control measures with a high coverage can stop a nascent pandemic. This can be applied to a community with a limited importation of cases but the quantity of antiviral drug needed would become rapidly prohibitive in case of further multiple foci. Both prophylactic and curative use of antiviral drugs can reduce the number of hospitalizations and the incidence during a pandemic. Finally, if a single strategy is sufficient to limit an outbreak in case of a moderate reproductive number, a combination of control measures is mandatory in case of highly transmissible strains. The results of these studies were taken in account to implement guidelines concerning antiviral drug use, in France.

Pandemic influenza planning in nursing homes: are we prepared?

Avian influenza or Influenza A (H5N1) is caused by a viral strain that occurs naturally in wild birds, but to which humans are immunologically naïve. If an influenza pandemic occurs, it is expected to have dire consequences, including millions of deaths, social disruption, and enormous economic consequences. The Department of Health and Human Resources plan, released in November 2005, clearly affirms the threat of a pandemic. Anticipating a disruption in many factions of society, every segment of the healthcare industry, including nursing homes, will be affected and will need to be self-sufficient. Disruption of vaccine distribution during the seasonal influenza vaccine shortage during the 2004/05 influenza season is but one example of erratic emergency planning. Nursing homes will have to make vital decisions and provide care to older adults who will not be on the initial priority list for vaccine. At the same time, nursing homes will face an anticipated shortage of antiviral medications and be expected to provide surge capacity for overwhelmed hospitals. This article provides an overview of current recommendations for pandemic preparedness and the potential effect of a pandemic on the nursing home industry. It highlights the need for collaborative planning and dialogue between nursing homes and various stakeholders already heavily invested in pandemic preparedness.

Social contacts of school children and the transmission of respiratory-spread pathogens

Empirical data about contact frequencies of children is needed for estimating parameters in mathematical modelling studies that investigate the effect of targeting influenza intervention to children. A survey about the social contacts of school children was conducted in a primary school in Germany. The distribution of the daily numbers of contacts was stratified by age of the contacted person and by weekday. A negative binomial regression analysis was performed to investigate factors that influence contact behaviour. Using logistic regression analysis we examined the relationship between the numbers of private contacts and having been ill in the last 6 months. We computed effective contact numbers to take the heterogeneity in contact behaviour into account in assessing the contribution of children's contacts to the overall transmission of an infection. The possible effects of intervention measures such as school closure and vaccination on the transmission of respiratory-spread agents to other age groups are discussed.

The influenza pandemic preparedness planning tool InfluSim

Background

Planning public health responses against pandemic influenza relies on predictive models by which the impact of different intervention strategies can be evaluated. Research has to date rather focused on producing predictions for certain localities or under specific conditions, than on designing a publicly available planning tool which can be applied by public health administrations. Here, we provide such a tool which is reproducible by an explicitly formulated structure and designed to operate with an optimal combination of the competing requirements of precision, realism and generality.

Results

InfluSim is a deterministic compartment model based on a system of over 1,000 differential equations which extend the classic SEIR model by clinical and demographic parameters relevant for pandemic preparedness planning. It allows for producing time courses and cumulative numbers of influenza cases, outpatient visits, applied antiviral treatment doses, hospitalizations, deaths and work days lost due to sickness, all of which may be associated with economic aspects. The software is programmed in Java, operates platform independent and can be executed on regular desktop computers.

Conclusion

InfluSim is an online available software which efficiently assists public health planners in designing optimal interventions against pandemic influenza. It can reproduce the infection dynamics of pandemic influenza like complex computer simulations while offering at the same time reproducibility, higher computational performance and better operability.

[Role of antiviral drugs in containing pandemic influenza. Contribution of recent modelling exercises synthesis prepared by the InVS/Inserm "epidemiology" group - November 2005]

The growing threat of influenza pandemic has lead many countries to stockpile specific antiviral drugs, mainly oseltamivir, as it can be used both for prophylaxis and therapy. Several recently published studies, based on mathematical modelling, have assessed the impact of a large scale use of this drug to contain an emerging pandemic, slow its spread within a country or reduce its epidemiological impact. They conclude that ring antiviral prophylaxis around the first cases, combined with social distancing measures, may halt a nascent pandemic, if the human-to-human transmissibility of the virus is limited and the control measures implemented promptly and with a high coverage. In case of failure, these same strategies could delay the spread of the virus within a country. The use of influenza antiviral drugs would reduce the burden of disease and even the clinical attack rate, under the assumption of a shorter infectious period for treated patients. These studies are in favour of stockpiling influenza antiviral drugs, at least to cover the curative needs and, even better, to contribute to the global effort to contain an emergent pandemic and to allow an intervention around the first chains of indigenous transmission in a country, thus slowing the virus spread. These results are based on the hypothesis of the effectiveness of oseltamivir on the pandemic virus and confirm the critical importance of a sensitive and reactive surveillance.