Spread Of Pandemic Influenza Research Articles

Discrete Stochastic Optimization for Public Health Interventions with Constraints

Many public health threats exist, motivating the need to find optimal intervention strategies. Given the stochastic nature of the threats (e.g., the spread of pandemic influenza, the occurrence of drug overdoses, and the prevalence of alcohol-related threats), deterministic optimization approaches may be inappropriate. In this paper, we implement a stochastic optimization method to address aspects of the 2009 H1N1 and the COVID-19 pandemics, with the spread of disease modeled by the open-source Monte Carlo simulations, FluTE, and Covasim, respectively. Without testing every possible option, the objective of the optimization is to determine the best combination of intervention strategies so as to result in minimal economic loss to society. To reach our objective, this application-oriented paper uses the discrete simultaneous perturbation stochastic approximation method (DSPSA), a recursive simulation-based optimization algorithm, to update the input parameters in the disease simulation software so that the output iteratively approaches minimal economic loss. Assuming that the simulation models for the spread of disease (FluTE for H1N1 and Covasim for COVID-19 in our case) are accurate representations for the population being studied, the simulation-based strategy we present provides decision makers a powerful tool to mitigate potential human and economic losses from any epidemic. The basic approach is also applicable in other public health problems, such as opioid abuse and drunk driving.

Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings-International Travel-Related Measures.

International travel–related nonpharmaceutical interventions (NPIs), which can include traveler screening, travel restrictions, and border closures, often are included in national influenza pandemic preparedness plans. We performed systematic reviews to identify evidence for their effectiveness. We found 15 studies in total. Some studies reported that NPIs could delay the introduction of influenza virus. However, no available evidence indicated that screening of inbound travelers would have a substantial effect on preventing spread of pandemic influenza, and no studies examining exit screening were found. Some studies reported that travel restrictions could delay the start of local transmission and slow international spread, and 1 study indicated that small Pacific islands were able to prevent importation of pandemic influenza during 1918–19 through complete border closure. This limited evidence base indicates that international travel-related NPIs would have limited effectiveness in controlling pandemic influenza and that these measures require considerable resources to implement.

Making Universal Influenza Vaccines: Lessons From the 1918 Pandemic.

The year 2018 marked the 100th anniversary of the deadliest event in human history. In 1918–1919, pandemic influenza spread globally and caused an estimated 50–100 million deaths associated with unexpected clinical and epidemiological features. The descendants of the 1918 virus continue to circulate as annual epidemic viruses causing significant mortality each year. The 1918 influenza pandemic serves as a benchmark for the development of universal influenza vaccines. Challenges to producing a truly universal influenza vaccine include eliciting broad protection against antigenically different influenza viruses that can prevent or significantly downregulate viral replication and reduce morbidity by preventing development of viral and secondary bacterial pneumonia. Perhaps the most important goal of such vaccines is not to prevent influenza, but to prevent influenza deaths.

Effectiveness of maternal influenza immunization in young infants in Japan.

Infants with influenza, particularly those younger than 1 year of age, are at high risk of developing a severe case or of dying. Recently, owing to the spread of pandemic influenza A (H1N1) 2009, the Advisory Committee on Immunization Practices recommended maternal immunization to reduce the risk of influenza infection in pregnant women and infants. Such reporting is rare in Japan. The aim of this study was therefore to investigate the effect on the newborn of influenza vaccination of pregnant women in Japan. The study included 200 infants who were born to healthy mothers at Kobayashi Ladies Clinic during influenza season from November 2010 to April 2011. The incidence of fever and laboratory-confirmed influenza was assessed in the infants for the 6 months after their birth. Of the 200 infants, four were excluded from this study due to loss to follow up. The 106 infants in the group whose mothers received the influenza vaccine (vaccinated group) before parturition were compared with the 90 infants in the group whose mothers did not receive the influenza vaccine (non-vaccinated group). Fever was noted in 36 infants (34.0%) in the vaccinated group and in 47 infants (52.2%) in the non-vaccinated group (P < 0.007), and the incidence of influenza was 0 (0%) and 5 (5.6%), respectively (P = 0.019). The incidence of fever and influenza among infants was significantly lower in the vaccinated group compared with the non-vaccinated group. Maternal influenza immunization should be actively recommended in Japan to protect newborns from influenza viruses.

Does the weather play a role in the spread of pandemic influenza? A study of H1N1pdm09 infections in France during 2009-2010.

Understanding patterns of influenza spread and persistence is crucial for pandemic preparedness. The H1N1pdm09 virus caused the first influenza pandemic of the 21st century which resulted in at least 18500 deaths. Based on laboratory-confirmed primary-care case reports we investigated the role of weather conditions and socio-demographic variables in its initial spread and subsequent presence in France. Our findings suggest that low relative humidity and high population density were determinants in shaping the early spread of the virus at the national level. Those conditions also favoured the persistence of viral presence throughout the first 33 weeks of the pandemic. Additionally this persistence was significantly favoured by low insolation. These results confirm the increasingly recognized role of humidity in influenza dynamics and underlie the concomitant effect of insolation. Therefore climatic factors should be taken into account when designing influenza control and prevention measures.

Population-level susceptibility, severity and spread of pandemic influenza: design of, and initial results from, a pre-pandemic and hibernating pandemic phase study using cross-sectional data from the Health Survey for England (HSE)

BackgroundAssessing severity and spread of a novel influenza strain at the start of a pandemic is critical for informing a targeted and proportional response. It requires community-level studies to estimate the burden of infection and disease. Rapidly initiating such studies in a pandemic is difficult. The study aims to establish an efficient system allowing real-time assessment of population susceptibility, spread of infection and clinical attack rates in the event of a pandemic.MethodsWe developed and appended additional survey questions and specimen collection to the Health Survey for England (HSE) – a large, annual, rolling nationally representative general population survey recruiting throughout the year – to enable rapid population-based surveys of influenza infection and disease during a pandemic. Using these surveys we can assess the spread of the virus geographically, by age and through time. The data generated can also provide denominators for national estimates of case fatality and hospitalisation rates.Phase 1: we compared retrospectively collected HSE illness rates during the first two infection waves of the 2009 pandemic with the Flu Watch study (a prospective community cohort). Monthly and seasonal age-specific rates of illness and proportion vaccinated were compared.Phase 2: we piloted blood specimen and data collection alongside the 2012–13 HSE. We are developing laboratory methods and protocols for real-time serological assays of a novel pandemic influenza virus using these specimens, and automated programmes for analysing and reporting illness and infection rates.Phase 3: during inter-pandemic years, the study enters a holding phase, where it is included in the yearly HSE ethics application and planning procedures, allowing rapid triggering in a pandemic.Phase 4: once retriggered, the study will utilise the methods developed in phase 2 to monitor the severity and spread of the pandemic in real time.ResultsPhase 1: the rates of reported illness during the first two waves in the HSE underestimated the community burden as measured by Flu Watch, but the patterns of illness by age and time were broadly comparable. The extent of underestimation was greatest for HSE participants interviewed later in the year compared with those interviewed closer to the pandemic. Vaccine uptake in the HSE study was comparable to independent national estimates and the Flu Watch study.Phases 2 and 3: illness data and serological samples from 2018 participants were collected in the 2012–13 HSE and transferred to the University College London Hospital. In the 2013 HSE and onwards, this project was included in the annual HSE ethics and planning rounds.ConclusionsThe HSE’s underestimation of illness rates during the first two waves of the pandemic is probably due to recall bias and the limitation of being able to report only one illness when multiple illnesses per season can occur. Changes to the illness questions (reporting only recent illnesses) should help minimise these issues. Additional prospective follow-up could improve measurement of disease incidence. The representative nature of the HSE allows accurate measurements of vaccine uptake.Study registrationThis study is registered as ISRCTN80214280.FundingThis project was funded by the NIHR Public Health Research programme and will be published in full inPublic Health Research; Vol. 3, No. 6. See the NIHR Journals Library website for further project information.

Evaluation of the spread of pandemic influenza A/H1N1 2009 among Japanese university students.

The pandemic influenza A/H1N1 2009 virus is commonly known to affect younger individuals. Several epidemiological studies have clarified the epidemic features of university students in Japan. In this study, we reviewed these studies in Japan in comparison with reports from other countries. The average cumulative incidence rate among university students was 9.6 %, with the major symptoms being cough, sore throat, and rhinorrhea. These epidemiological features were similar between Japan and other countries. Attitudes and behaviors toward pandemic influenza control measures were different before and improved during and after the epidemic. These features were also similar to those in other countries. On the other hand, the epidemic spread through club activities or social events, and transmission was attenuated after temporary closure of such groups in Japan. This transmission pattern was inconsistent among countries, which may have been due to differences in lifestyle and cultural habits. Based on these results, infection control measures of pandemic influenza for university organizations in Japan should be considered.

Spatial Transmission of 2009 Pandemic Influenza in the US.

The 2009 H1N1 influenza pandemic provides a unique opportunity for detailed examination of the spatial dynamics of an emerging pathogen. In the US, the pandemic was characterized by substantial geographical heterogeneity: the 2009 spring wave was limited mainly to northeastern cities while the larger fall wave affected the whole country. Here we use finely resolved spatial and temporal influenza disease data based on electronic medical claims to explore the spread of the fall pandemic wave across 271 US cities and associated suburban areas. We document a clear spatial pattern in the timing of onset of the fall wave, starting in southeastern cities and spreading outwards over a period of three months. We use mechanistic models to tease apart the external factors associated with the timing of the fall wave arrival: differential seeding events linked to demographic factors, school opening dates, absolute humidity, prior immunity from the spring wave, spatial diffusion, and their interactions. Although the onset of the fall wave was correlated with school openings as previously reported, models including spatial spread alone resulted in better fit. The best model had a combination of the two. Absolute humidity or prior exposure during the spring wave did not improve the fit and population size only played a weak role. In conclusion, the protracted spread of pandemic influenza in fall 2009 in the US was dominated by short-distance spatial spread partially catalysed by school openings rather than long-distance transmission events. This is in contrast to the rapid hierarchical transmission patterns previously described for seasonal influenza. The findings underline the critical role that school-age children play in facilitating the geographic spread of pandemic influenza and highlight the need for further information on the movement and mixing patterns of this age group.

Assessment of the Intensive Countermeasures in the 2009 Pandemic Influenza in Korea

ObjectivesIt is critical to implement effective multiple countermeasures to mitigate or retain the spread of pandemic influenza. We propose a mathematical pandemic influenza model to assess the effectiveness of multiple countermeasures implemented in 2009. MethodsAge-specific parameters, including the transmission rate, the proportion of asymptomatic individuals, the vaccination rate, the social distancing rate, and the antiviral treatment rate are estimated using the least-square method calibrated to the incidence data. ResultsThe multiple interventions (intensive vaccination, social distancing, antivrial treatment) were successfully implemented resulting in the dramatic reduction in the total number of incidence. ConclusionThe model output is sensitive to age-specific parameters and this leads to the fact that a more elaborate age group model should be developed and extensive further studies must be followed.

Impact of 2009 pandemic influenza among Vietnamese children based on a population‐based prospective surveillance from 2007 to 2011

BackgroundInfluenza virus is one of the major viral pathogens causing pediatric acute respiratory infection (ARI). The spread of pandemic influenza A (A(H1N1)pdm09) in 2009 around the globe had a huge impact on global health.ObjectiveTo investigate the impact of A(H1N1)pdm09 on pediatric ARI in Vietnam.Study designAn ongoing population-based prospective surveillance in central Vietnam was used. All children aged <15 years residing in Nha Trang city, enrolled to the ARI surveillance in Khanh Hoa General Hospital, from February 2007 through March 2011 were studied. Clinical data and nasopharyngeal swab samples were collected. Influenza A was detected and genotyped by multiplex polymerase chain reaction assays and sequencing.ResultsAmong enrolled 2736 hospitalized ARI cases, 354 (13%) were positive for influenza A. Genotyping results revealed that seasonal H3N2 and H1N1 (sea-H1N1) viruses were cocirculating before A(H1N1)pdm09 appeared in July 2009. The A(H1N1)pdm09 replaced the sea-H1N1 after the pandemic. The majority of influenza A cases (90%) were aged <5 years with incidence rate of 537 (387–775) per 100 000 population. Annual incidence rates of hospitalized influenza cases for pre-, initial and post-pandemic periods among children aged <5 year were 474, 452, and 387 per 100 000, respectively. Children with A(H1N1)pdm09 were elder, visited the hospital earlier, less frequently had severe signs, and were less frequently associated with viral coinfection compared with seasonal influenza cases.ConclusionsThe A(H1N1)pdm09 did not increase the influenza annual hospitalization incidence or disease severity compared with seasonal influenza among pediatric ARI cases in central Vietnam.

Effect of air travel on the spread of an avian influenza pandemic to the United States

The highly pathogenic avian influenza (HPAI) strain H5N1, which first appeared in Hong Kong in 1997, achieved bird-to-human transmission, causing a severe disease with high mortality to humans [18]. According to the World Health Organization (WHO), a total of 637 cases were reported in fifteen countries, including 378 deaths, corresponding to a case fatality rate of nearly 60% [19]. Avian influenza continues to be one of the deadliest diseases that jumps from animals to humans. Epidemiologists believe that it is likely to cause the next major global pandemic that could kill millions of people.The 2002 outbreak of severe acute respiratory syndrome (SARS) demonstrated that international air travel can significantly influence the global spread of an infectious disease. This paper studies the effects of air travel on the spread of avian influenza from Asian and Australian cities to the United States. A two-city mathematical model involving a pandemic strain is used to derive the basic reproduction number (R0), which determines if the disease will spread and persist (R0>1) or go extinct (R0<1). Real air travel data is used to model the disease spread by individuals who are susceptible to or are infected with pandemic avian influenza. Analysis of the two-city model helps understand the dynamics of the spread of pandemic influenza when the cities are connected by air travel. Understanding these effects can help public health officials and policy-makers select the appropriate disease control measures. Also, it can provide guidance to decision-makers on where to implement control measures while conserving precious resources.

Pandemic influenza in Papua New Guinea: a modelling study comparison with pandemic spread in a developed country

ObjectivesThe possible occurrence of a highly pathogenic influenza strain is of concern to health authorities worldwide. It is known that during past influenza pandemics developing countries have experienced considerably higher...

Description of a large urban school-located 2009 pandemic H1N1 vaccination campaign, New York City 2009-2010.

In the spring of 2009, New York City (NYC) experienced the emergence and rapid spread of pandemic influenza A H1N1 virus (pH1N1), which had a high attack rate in children and caused many school closures. During the 2009 fall wave of pH1N1, a school-located vaccination campaign for elementary schoolchildren was conducted in order to reduce infection and transmission in the school setting, thereby reducing the impact of pH1N1 that was observed earlier in the year. In this paper, we describe the planning and outcomes of the NYC school-located vaccination campaign. We compared consent and vaccination data for three vaccination models (school nurse alone, school nurse plus contract nurse, team). Overall, >1,200 of almost 1,600 eligible schools participated, achieving 26.8% consent and 21.5% first-dose vaccination rates, which did not vary significantly by vaccination model. A total of 189,902 doses were administered during two vaccination rounds to 115,668 students at 998 schools included in the analysis; vaccination rates varied by borough, school type, and poverty level. The team model achieved vaccination of more children per day and required fewer vaccination days per school. NYC's campaign is the largest described school-located influenza vaccination campaign to date. Despite substantial challenges, school-located vaccination is feasible in large, urban settings, and during a public health emergency.

Effects of School Closure on Incidence of Pandemic Influenza in Alberta, Canada

Control of pandemic influenza by social-distancing measures, such as school closures, is a controversial aspect of pandemic planning. However, investigations of the extent to which these measures actually affect the progression of a pandemic have been limited. To examine correlations between the incidence of pandemic H1N1 (pH1N1) influenza in Alberta, Canada, in 2009 and school closures or weather changes, and to estimate the effects of school closures and weather changes on pH1N1 transmission. Mathematical transmission models were fit to data that compared the pattern of confirmed pH1N1 cases with the school calendar and weather patterns. Alberta, Canada, from 19 April 2009 to 2 January 2010. 2009 virologic test results, 2006 census data, 2009 daily temperature and humidity data, and 2009 school calendars. Age-specific daily counts of positive results for pH1N1 from the complete database of 35 510 specimens submitted to the Alberta Provincial Laboratory for Public Health for virologic testing from 19 April 2009 to 2 January 2010. The ending and restarting of school terms had a major effect in attenuating the first wave and starting the second wave of pandemic influenza cases. Mathematical models suggested that school closure reduced transmission among school-age children by more than 50% and that this was a key factor in interrupting transmission. The models also indicated that seasonal changes in weather had a significant effect on the temporal pattern of the epidemic. Data probably represent a small sample of all viral infections. The mathematical models make simplifying assumptions in order to make simulations and analysis feasible. Analysis of data from unrestricted virologic testing during an influenza pandemic provides compelling evidence that closing schools can have dramatic effects on transmission of pandemic influenza. School closure seems to be an effective strategy for slowing the spread of pandemic influenza in countries with social contact networks similar to those in Canada. Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, and Public Health Agency of Canada.

Risk factors for acute respiratory distress syndrome development in patients with type A influenza (H1N1)

Acute respiratory distress syndrome (ARDS) is a significant complication in patients with type A influenza (H1N1) due to the severity of the disease and adverse outcome. The aim of the study was to identify risk factors for the development of ARDS in patients with type A influenza (H1N1) and outcome of ARDS. The research was conducted as a case series study, and included patients admitted at the Clinical Center in Kragujevac during the 2009 and 2010 flu season. Data for the study were obtained from patients' medical records, inclusion criteria having been determined in accordance with recommendations of the Expert Methodological Guide for Controlling Spread of Pandemic Influenza in the Republic of Serbia. Primary data analysis was performed using descriptive statistics and a statistical method for testing hypotheses. Dependence analysis was performed using simple logistic regression. The statistical hypotheses were tested at the 0.05 level of significance. The case group consisted of 14 patients who developed ARDS, while the control group was composed of 34 patients with influenza but without ARDS (group alignment performed by age). Simple logistic regression analysis identified the following risk factors for the development of ARDS: diabetes mellitus type 1 or 2 (p=0.028), high levels of C-reactive protein (p=0.004), aspartate-aminotransferase (p=0.006), urea (p=0.028), creatine kinase (p=0.001), lactate-dehydrogenase (p=0.005) and longer time elapsed from disease symptoms onset to the administration of specific antiviral therapy administration (p=0.021). The research showed that diabetes, late initiation of antiviral therapy and some laboratory tests are risk factors for ARDS development in patients with type A influenza (H1N1).

Mass death and mass illness in an isolated Canadian town: coping with pandemic influenza in Kenora, Ontario, in 1918–1921

In 1918–1920, pandemic influenza spread across Canada and around the world, striking in three separate waves. The majority of existing research on the Canadian experience during the second and most deadly wave of the epidemic suggests that there were enormous difficulties in dealing with the dead. While it seemed likely that Kenora, an isolated Northern Ontario community, would have faced the same challenges, this was not entirely the case. There were changes in death rituals: for example, church services were banned so that funerals had to be held in homes or at gravesides. Surprisingly, though the death rate in Kenora during the peak would reach nearly 30 times normal, the handling of the dead does not seem to have become a significant issue. During the fall and winter of 1918, the largest concern for the communities of Kenora and Keewatin (the two were separate communities at this time) was not responding to the demand for daily burials, but attempting to prevent further infection in the community.

Australian Aboriginal and Torres Strait Islander communities and the development of pandemic influenza containment strategies: Community voices and community control

Objectives To develop culturally appropriate and effective strategies to reduce the risk from pandemic influenza (H1N109) in rural and remote Australian Aboriginal and Torres Strait Islander communities. Methods Participatory Action Research (PAR) approach that enabled communities and researchers to work together to develop understanding and take action to reduce risk. Results The H1N109 pandemic raised deep concerns and serious issues in all of the Aboriginal and Torres Strait Islander communities involved in this project. The participants expressed distrust and scepticism in relation to current Australian health policies on containment and told the researchers that specific plans for Aboriginal and Torres Strait Islander peoples were needed. Respondents indicated that policies and plans had been developed without respectful engagement with communities. The strong and recurring themes that emerged from the PAR cycles were: the importance of family; ways of life and realities of living in response to influenza; and key messages to government and health services to focus on communication, understanding and respect. Conclusion The essential work of reducing risk of pandemic influenza with Aboriginal and Torres Strait Islander communities is not straightforward, but this project has highlighted a number of useful pathways to continue to journey along with communities. A number of strategies to reduce the spread of pandemic influenza in Aboriginal and Torres Strait Islander communities were identified. These strategies would make a good starting point for conversations with communities and health services. In Aboriginal and Torres Strait Islander communities the environment, community structures and traditions vary. Respectful engagement with communities is needed to develop effective policy.

The Global Transmission and Control of Influenza

New strains of influenza spread around the globe via the movement of infected individuals. The global dynamics of influenza are complicated by different patterns of influenza seasonality in different regions of the world. We have released an open-source stochastic mathematical model of the spread of influenza across 321 major, strategically located cities of the world. Influenza is transmitted between cities via infected airline passengers. Seasonality is simulated by increasing the transmissibility in each city at the times of the year when influenza has been observed to be most prevalent. The spatiotemporal spread of pandemic influenza can be understood through clusters of global transmission and links between them, which we identify using the epidemic percolation network (EPN) of the model. We use the model to explain the observed global pattern of spread for pandemic influenza A(H1N1) 2009–2010 (pandemic H1N1 2009) and to examine possible global patterns of spread for future pandemics depending on the origin of pandemic spread, time of year of emergence, and basic reproductive number (). We also use the model to investigate the effectiveness of a plausible global distribution of vaccine for various pandemic scenarios. For pandemic H1N1 2009, we show that the biggest impact of vaccination was in the temperate northern hemisphere. For pandemics starting in the temperate northern hemisphere in May or April, vaccination would have little effect in the temperate southern hemisphere and a small effect in the tropics. With the increasing interconnectedness of the world's population, we must take a global view of infectious disease transmission. Our open-source, computationally simple model can help public health officials plan for the next pandemic as well as deal with interpandemic influenza.

A simulation model for policy decision analysis: a case of pandemic influenza on a university campus

Pandemic influenza preparedness plans strongly focus on efficient mitigation strategies including social distancing, logistics and medical response. These strategies are formed by multiple decision makers before a pandemic outbreak and during the pandemic in local communities, states and nation-wide. In this paper, we model the spread of pandemic influenza in a local community, a university, and evaluate the mitigation policies. Since the development of an appropriate vaccine requires a significant amount of time and available antiviral quantities can only cover a relatively small proportion of the population, university decision makers will first focus on non-pharmaceutical interventions. These interventions include social distancing and isolation. The disease spread is modelled as differential equations-based compartmental model. The system is simulated for multiple non-pharmaceutical interventions such as social distancing including suspending university operations, evacuating dorms and isolation of infected individuals on campus. Although the model is built based on the preparedness plan of one of the biggest universities in the world, Arizona State University, it can easily be generalized for other colleges and universities. The policies and the decisions are tested by several simulation runs and evaluations of the mitigation strategies are presented in the paper.

Early spread of the 2009 influenza A(H1N1) pandemic in the United Kingdom – use of local syndromic data, May–August 2009

Following the confirmation of the first two cases of pandemic influenza on 27 April 2009 in the United Kingdom (UK), syndromic surveillance data from the Health Protection Agency (HPA)/QSurveillance and HPA/NHS Direct systems were used to monitor the possible spread of pandemic influenza at local level during the first phase of the outbreak. During the early weeks, syndromic indicators sensitive to influenza activity monitored through the two schemes remained low and the majority of cases were travel-related. The first evidence of community spread was seen in the West Midlands region following a school-based outbreak in central Birmingham. During the first phase several Primary Care Trusts had periods of exceptional influenza activity two to three weeks ahead of the rest of the region. Community transmission in London began slightly later than in the West Midlands but the rates of influenza-like illness recorded by general practitioners (GPs) were ultimately higher. Influenza activity in the West Midlands and London regions peaked a week before the remainder of the UK. Data from the HPA/NHS Direct and HPA/QSurveillance systems were mapped at local level and used alongside laboratory data and local intelligence to assist in the identification of hotspots, to direct limited public health resources and to monitor the progression of the outbreak. This work has demonstrated the utility of local syndromic surveillance data in the detection of increased transmission and in the epidemiological investigation of the pandemic and has prompted future spatio-temporal work.