Sandip Mandal | Tokyo University of Marine Science and Technology (original) (raw)

Papers by Sandip Mandal

Summary Background The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosi... more Summary Background The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75% reduction in mortality from tuberculosis by 2025. We aimed to assess whether these targets are feasible in three high-burden countries with contrasting epidemiology and previous programmatic achievements.

Scientific Reports, 2021

India’s lockdown and subsequent restrictions against SARS-CoV-2, if lifted without any other miti... more India’s lockdown and subsequent restrictions against SARS-CoV-2, if lifted without any other mitigations in place, could risk a second wave of infection. A test-and-isolate strategy, using PCR diagnostic tests, could help to minimise the impact of this second wave. Meanwhile, population-level serological surveillance can provide valuable insights into the level of immunity in the population. Using a mathematical model, consistent with an Indian megacity, we examined how seroprevalence data could guide a test-and-isolate strategy, for fully lifting restrictions. For example, if seroprevalence is 20% of the population, we show that a testing strategy needs to identify symptomatic cases within 5–8 days of symptom onset, in order to prevent a resurgent wave from overwhelming hospital capacity in the city. This estimate is robust to uncertainty in the effectiveness of the lockdown, as well as in immune protection against reinfection. To set these results in their economic context, we est...

Journal of Plankton Research, 2016

Highly intermittent spatial variability of phytoplankton is observed ubiquitously in marine ecosy... more Highly intermittent spatial variability of phytoplankton is observed ubiquitously in marine ecosystems, especially when measurements are performed at the micro-scale level. Therefore, theoretical developments and new modelling tools are required to understand the observed small-scale vertical structure and its relationship to ecosystem behaviour. Nearly all current ecosystem models are formulated entirely based on the mean field approximation, ignoring subgrid scale variability. Even if such approximation may be reasonable for meso-scales (and above), it cannot account for micro-scale dynamics, which may also impact macroscopic properties at the larger scale. To consider intermittency of variables in plankton ecosystem models, we apply a newly developed modelling approach called the closure approach. Detailed simulations were conducted, combining fluid-dynamics of the 1D water column with the nutrient-phytoplankton closure ecosystem model for application to a site in the northern North Sea. Compared with a control model, which does not account for such intermittency, the closure model produced substantially different spatio-temporal patterns of mean phytoplankton biomass and growth rate, which depended on the overall level of variability. In this study, we (i) seek to explore the effects of sub-scale variability coupled with physical transport and (ii) begin to address the yet unresolved question of how to consistently model the advection and diffusion of the variances and co-variances used to represent sub-scale variability in the closure approach. Our results suggest that it may be necessary to account explicitly for the intermittent distribution of plankton and nutrients, even in large-scale biogeochemical models.

Epidemiology, 2009

Background: Exposure to air pollutants has been related to preterm birth, but little evidence can... more Background: Exposure to air pollutants has been related to preterm birth, but little evidence can be available for PM 2.5 , O 3 and CO in China. This study aimed to investigate the short-term effect of exposure to air pollutants on risk preterm birth during 2014-2016 in Ningbo, China. Methods: We conducted a time-series study to evaluate the associations between daily preterm birth and major air pollutants (including PM 2.5 , PM 10 , SO 2 , NO 2 , O 3 and CO) in Ningbo during 2014-2016. A General Additive Model extend Poisson regression was used to evaluate the relationship between preterm birth and air pollution with adjustment for time-trend, meteorological factors and day of the week (DOW). We also conducted a subgroup analysis by season and age. Results: In this study, a total of 37,389 birth occurred between 2014 and 2016 from the Electronic Medical Records System of Ningbo Women and Children's Hospital, of which 5428 were verified as preterm birth. The single pollutant model suggested that lag effect of PM 2.5 , PM 10 , NO 2 reached a peak at day 3 before delivery and day 6 for SO 2 , and no relationships were observed for O 3 and preterm birth. Excess risks (95% confidence intervals) for an increase of IQR of air pollutant concentrations were 4.84 (95% CI: 1.77, 8.00) for PM 2.5 , 3.56 (95% CI: 0.07, 7.17) for PM 10 , 3.65 (95% CI: 0.86, 6.51) for SO 2 , 6.49 (95% CI: 1.86, 11.34) for NO 2 , − 0.90 (95% CI:-4.76, 3.11) for O 3 , and 3.36 (95% CI: 0.50, 6.30) for CO. Sensitivity analyses by exclusion of maternal age < 18 or > 35 years did not materially alter our results. Conclusions: This study indicates that short-term exposure to air pollutants (including PM 2.5 , PM 10 , SO 2 , NO 2) are positively associated with risk of preterm birth in Ningbo, China.

BMC Medicine, 2020

Background: The prevention of tuberculosis (TB) is key for accelerating current, slow declines in... more Background: The prevention of tuberculosis (TB) is key for accelerating current, slow declines in TB burden. The 2018 World Health Organization (WHO) guidelines on eligibility for preventive therapy to treat latent TB infection (LTBI) include people living with human immunodeficiency virus (PLHIV), household contacts of TB patients including children, and those with clinical conditions including silicosis, dialysis, transplantation, etc. and other country-specific groups. We aimed to estimate the potential impact of full implementation of these guidelines in the WHO SouthEast Asian (SEA) Region, which bears the largest burden of TB and LTBI amongst the WHO regions. Methods: We developed mathematical models of TB transmission dynamics, calibrated individually to each of the 11 countries in the region. We modelled preventive therapy in the absence of other TB interventions. As an alternative comparator, reflecting ongoing developments in TB control in the region, we also simulated improvements in the treatment cascade for active TB, including private sector engagement and intensified casefinding. Relative to both scenarios, for each country in the region, we projected TB cases and deaths averted between 2020 and 2030, by full uptake of preventive therapy, defined as comprehensive coverage amongst eligible populations as per WHO guidelines, and assuming outcomes consistent with clinical trials. We also performed sensitivity analysis to illustrate impact under less-than-optimal conditions. Results: At the regional level, full uptake of preventive therapy amongst identified risk groups would reduce annual incidence rates in 2030 by 8.30% (95% CrI 6.48-10.83) relative to 2015, in the absence of any additional interventions. If implemented against a backdrop of improved TB treatment cascades, preventive therapy would achieve an incremental 6.93 percentage points (95% CrI 5.81-8.51) of reduction in annual incidence rates, compared to 2015. At the regional level, the numbers of individuals with latent TB infection that need to be treated to avert 1 TB case is 64 (95% CrI 55-74). Sensitivity analysis illustrates that results for impact are roughly proportional to 'effective coverage' (the product of actual coverage and effectiveness of the regimen). Conclusions: Full implementation of WHO guidelines is important for ending TB in the SEA Region. Although future strategies will need to be expanded to the population level, to achieve large declines in TB incidence, the uptake of current tools can offer a valuable step in this direction.

BMJ Global Health, 2020

The Southeast Asia Region continues to battle tuberculosis (TB) as one of its most severe health ... more The Southeast Asia Region continues to battle tuberculosis (TB) as one of its most severe health and development challenges. Unless there is a substantial increase in investments for TB prevention, diagnosis, care and treatment, there will be catastrophic effects for the region. The uncontrolled TB burden impacts socioeconomic development and increase of drug resistance in the region. Based on epidemiological inputs from a mathematical model, a costing analysis estimates that the desired targets of ending TB are achievable with additional interventions, and critical thresholds require an increase in spending by almost double the current levels. The data source for financial allocation to TB programmes is the report submitted by countries to WHO, while projections are based on modelling. The model accounts for funding needs for all strategies based on published data and accounts for programme and patient costs. This paper delineates the resource needs, availability and gaps of ending...

Journal of Biological Dynamics, 2018

Global eradication of Guinea worm disease (GWD) is in the final stage but a mysterious epidemic o... more Global eradication of Guinea worm disease (GWD) is in the final stage but a mysterious epidemic of the parasite in dog population makes the elimination programme challenging. There is neither a vaccine nor an effective treatment against the disease and therefore intervention strategies rely on the current epidemiological understandings to control the spread of the disease. A novel mathematical model can predict the future outbreaks and it can quantify the dissemination rates of control interventions. Due to the lack of such novel models, a realistic mathematical model of GWD dynamics with human population, dog population, copepod population and the worm larvae is proposed and analyzed. Considering case data from Chad, we calibrate the model and perform global sensitivity analysis of the basic reproduction number with respect to the control parameters and copepod consumption rates. Furthermore, we investigate the impact of three control interventions: awareness of humans, isolation of infected dogs and copepod clearance from contaminated water sources. We also address the impact of combination interventions which leads to the conclusion that the combination of isolating the infected dogs and treating the contaminated ponds is a plausible way for eliminating the burden of GWD from Chad.

Objectives To investigate the impact of targeted vaccination strategies on morbidity and mortalit... more Objectives To investigate the impact of targeted vaccination strategies on morbidity and mortality due to COVID-19, as well as on the incidence of SARS-CoV-2, in India. Design Mathematical modelling. Settings Indian epidemic of COVID-19 and vulnerable population. Data sources Country specific and age-segregated pattern of social contact, case fatality rate and demographic data obtained from peer-reviewed literature and public domain. Model An age-structured dynamical model describing SARS-CoV-2 transmission in India incorporating uncertainty in natural history parameters was constructed. Interventions Comparison of different vaccine strategies by targeting priority groups such as key workers including health care professionals, individuals with comorbidities (24 - 60 year), and all above 60. Main outcome measures Incidence reduction and averted deaths in different scenarios, assuming that the current restrictions are fully lifted as vaccination is implemented. Results The priority g...

Frontiers in Marine Science

Previous modeling studies have shown that observed micro-scale (mm) variability of nutrients and ... more Previous modeling studies have shown that observed micro-scale (mm) variability of nutrients and phytoplankton biomass can strongly impact the large-scale mean growth response of phytoplankton in ways that cannot be represented by typical models based on the mean field approximation. Also, models accounting for the flexible eco-physiology of phytoplankton predict quite different responses to changing environmental conditions compared to most current (inflexible) models. Combining these two ideas for nutrient-phytoplankton systems we have developed a new "Flexible NP closure model" to represent competition among the three typically observed phytoplankton size classes: pico-, nano-, and micro-phytoplankton. Both micro-scale variability and flexible eco-physiology are expected to impact the competition among these size classes. With this work we begin to address how both these factors determine the size structure and size diversity of phytoplankton in the ocean. Under eutrophic conditions, variability does not impact the modeled growth rate of any size class. On the other hand, under oligotrophic conditions, variability preferentially enhances the biomass of the largest typically observed micro-size class, and reduces the biomass of the smallest nano-and intermediate pico-size classes.

India's lockdown against SARS-CoV-2, if lifted without any other mitigations in place, could ... more India's lockdown against SARS-CoV-2, if lifted without any other mitigations in place, could risk a second wave of infection. A test-and-isolate strategy, using PCR diagnostic tests, could help to minimise the impact of this second wave. Meanwhile, population-level serological surveillance can provide valuable insights into the level of immunity in the population. Using a mathematical model, consistent with an Indian megacity, we examined how seroprevalence data could guide a test-and-isolate strategy, for lifting a lockdown. For example, if seroprevalence is 20% of the population, we show that a testing strategy needs to identify symptomatic cases within 5 - 8 days of symptom onset, in order to prevent a resurgent wave from overwhelming hospital capacity in the city. This estimate is robust to uncertainty in the effectiveness of the lockdown, as well as in immune protection against reinfection. To set these results in their economic context, we estimate that the weekly cost of ...

Indian Journal of Medical Research

Nonlinear Analysis: Modelling and Control

This work deals with analytical investigation of local qualitative temporal behavior around inner... more This work deals with analytical investigation of local qualitative temporal behavior around inner equilibrium point of a model for three species food chain, studied earlier by Hastings and Powel and others. As an initial step towards the spectral analysis of the model, the governing equations have been split into linear and nonlinear parts around arbitrary equilibrium point. The explicit parameter dependence of eigenvalues of Jacobi matrix associated to the linear part have been derived. Analyzing these expressions in conjunction with some pedagogical analysis, a lot of predictions on stable, unstable or chaotic change of species have been highlighted. Agreement of predictions of this work with available numerical or semi-analytical studies suggest the utility of analytical results derived here for further investigation/analysis of the model as desired by earlier works.

Indian Journal of Medical Research

Journal of Theoretical Biology

BMC Medicine, 2017

Background: Against the backdrop of renewed efforts to control tuberculosis (TB) worldwide, there... more Background: Against the backdrop of renewed efforts to control tuberculosis (TB) worldwide, there is a need for improved methods to estimate the public health impact of TB programmes. Such methods should not only address the improved outcomes amongst those receiving care but should also account for the impact of TB services on reducing transmission. Methods: Vital registration data in India are not sufficiently reliable for estimates of TB mortality. As an alternative approach, we developed a mathematical model of TB transmission dynamics and mortality, capturing the scale-up of DOTS in India, through the rollout of the Revised National TB Control Programme (RNTCP). We used available data from the literature to calculate TB mortality hazards amongst untreated TB; amongst cases treated under RNTCP; and amongst cases treated under non-RNTCP conditions. Using a Bayesian evidence synthesis framework, we combined these data with current estimates for the TB burden in India to calibrate the transmission model. We simulated the national TB epidemic in the presence and absence of the DOTS programme, measuring lives saved as the difference in TB deaths between these scenarios. Results: From 1997 to 2016, India's RNTCP has saved 7.75 million lives (95% Bayesian credible interval 6.29-8.82 million). We estimate that 42% of this impact was due to the 'indirect' effects of the RNTCP in averting transmission as well as improving treatment outcomes. Conclusions: When expanding high-quality TB services, a substantial proportion of overall impact derives from preventive, as well as curative, benefits. Mathematical models, together with sufficient data, can be a helpful tool in estimating the true population impact of major disease control programmes.

The Lancet. Global health, Nov 5, 2016

The post-2015 End TB Strategy sets global targets of reducing tuberculosis incidence by 50% and m... more The post-2015 End TB Strategy sets global targets of reducing tuberculosis incidence by 50% and mortality by 75% by 2025. We aimed to assess resource requirements and cost-effectiveness of strategies to achieve these targets in China, India, and South Africa. We examined intervention scenarios developed in consultation with country stakeholders, which scaled up existing interventions to high but feasible coverage by 2025. Nine independent modelling groups collaborated to estimate policy outcomes, and we estimated the cost of each scenario by synthesising service use estimates, empirical cost data, and expert opinion on implementation strategies. We estimated health effects (ie, disability-adjusted life-years averted) and resource implications for 2016-35, including patient-incurred costs. To assess resource requirements and cost-effectiveness, we compared scenarios with a base case representing continued current practice. Incremental tuberculosis service costs differed by scenario a...

The Lancet. Global health, Nov 5, 2016

The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75%... more The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75% reduction in mortality from tuberculosis by 2025. We aimed to assess whether these targets are feasible in three high-burden countries with contrasting epidemiology and previous programmatic achievements. 11 independently developed mathematical models of tuberculosis transmission projected the epidemiological impact of currently available tuberculosis interventions for prevention, diagnosis, and treatment in China, India, and South Africa. Models were calibrated with data on tuberculosis incidence and mortality in 2012. Representatives from national tuberculosis programmes and the advocacy community provided distinct country-specific intervention scenarios, which included screening for symptoms, active case finding, and preventive therapy. Aggressive scale-up of any single intervention scenario could not achieve the post-2015 End TB Strategy targets in any country. However, the models p...

Preface v List of symbols vii List of abbreviations x Chapter 1 Introduction and Objectives Chapt... more Preface v List of symbols vii List of abbreviations x Chapter 1 Introduction and Objectives Chapter 2 Concept of Exergy and Ascendency 2.1 Introduction 2.2 Classical thermodynamics 2.3 Statistical thermodynamics 2.4 Concept of exergy 2.5 Concept of ascendency Chapter 3 Numerical aspects of modified Hastings and Powell model 3.1 3.5.1 Result of numerical evolution of Hastings and Powell model considering TPP 3.5.2 Conclusion Chapter 4 Linear stability analysis of nonlinear aquatic ecosystem model 4.1 Introduction CONTENTS iv 4.2 The mathematical model 4.3 Determination of equilibrium points 4.4 Hartman-Grobman theorem 4.5 Methodology of linear stability analysis around equilibrium points 4.6 Some terminology associated with fixed points 4.7 Behaviour of the aquatic ecosystem around equilibrium points 4.8 Conclusion Chapter 5 Center manifold reduction of Hastings and Powell model around non vanishing equilibrium point 5.1 Introduction 5.2 Center manifolds depending on parameters 5.3 Computation of center manifold 5.4 Example 5.5 Center manifold reduction of Hastings and Powell model around non vanishing equilibrium point 5.6 Result and Discussion Chapter 6 Conclusions and Future scopes 6.1 Conclusions 6.2 Future scopes Appendix A Eigen values of the matrix of the linear part of Hastings and Powell model for all parameters B Table presenting bifurcation points and its behavior for different parameter values References Preface vi Further, in this book, different mathematical techniques like spectral analysis, central manifold reduction, construction of Lyapunov coefficient and function have been used, to predict the analytic dependence of equilibrium points on parameters and to understand the change of their behaviours for variations of parameters which lead to switch over the model system in different states. Bifurcation analysis is also followed as a subject of classical mathematical origins. However the modern development of the subject followed with qualitative theory of differential equations pioneered by Poincaré. We are grateful to Elena Chercunova, Acquisition Editor of LAP Lambert Academic Publishing, Germany, for inviting us to write a book from our research area and her support and suggestion for doing this.

Indian Journal of Physics, 2004

ABSTRACT We review some calculations to demonstrate the basic properties of biological pattern fo... more ABSTRACT We review some calculations to demonstrate the basic properties of biological pattern formation obtained from some models. Assuming a shallow gradient of source distribution, one can show that a striking pattern of activator concentration may be obtained with a maximum at the terminal of high source density from three models viz. depletion model, activator-inhibitor model assuming common sources and that with different sources.

Ecology, 2015

Fishing is expected to alter the spatial heterogeneity of fishes. As an effective index to quanti... more Fishing is expected to alter the spatial heterogeneity of fishes. As an effective index to quantify spatial heterogeneity, the exponent b in Taylor&amp;amp;amp;amp;amp;amp;#39;s power law (V = aMb) measures how spatial variance (V) varies with changes in mean abundance (M) of a population, with larger b indicating higher spatial aggregation potential (i.e., more heterogeneity). Theory predicts b is related with life history traits, but empirical evidence is lacking. Using 50-yr spatiotemporal data from the California Current Ecosystem, we examined fishing and life history effects on Taylor&amp;amp;amp;amp;amp;amp;#39;s exponent by comparing spatial distributions of exploited and unexploited fishes living in the same environment. We found that unexploited species with smaller size and generation time exhibit larger b, supporting theoretical prediction. In contrast, this relationship in exploited species is much weaker, as the exponents of large exploited species were higher than unexploited species with similar traits. Our results suggest that fishing may increase spatial aggregation potential of a species, likely through degrading their size/age structure. Results of moving-window cross-correlation analyses on b vs. age structure indices (mean age and age evenness) for some exploited species corroborate our findings. Furthermore, through linking our findings to other fundamental ecological patterns (occupancy-abundance and size-abundance relationships), we provide theoretical arguments for the usefulness of monitoring the exponent b for management purposes. We propose that age/size-truncated species might have lower recovery rate in spatial occupancy, and the spatial variance-mass relationship of a species might be non-linear. Our findings provide theoretical basis explaining why fishery management strategy should be concerned with changes to the age and spatial structure of exploited fishes.

Summary Background The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosi... more Summary Background The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75% reduction in mortality from tuberculosis by 2025. We aimed to assess whether these targets are feasible in three high-burden countries with contrasting epidemiology and previous programmatic achievements.

Scientific Reports, 2021

India’s lockdown and subsequent restrictions against SARS-CoV-2, if lifted without any other miti... more India’s lockdown and subsequent restrictions against SARS-CoV-2, if lifted without any other mitigations in place, could risk a second wave of infection. A test-and-isolate strategy, using PCR diagnostic tests, could help to minimise the impact of this second wave. Meanwhile, population-level serological surveillance can provide valuable insights into the level of immunity in the population. Using a mathematical model, consistent with an Indian megacity, we examined how seroprevalence data could guide a test-and-isolate strategy, for fully lifting restrictions. For example, if seroprevalence is 20% of the population, we show that a testing strategy needs to identify symptomatic cases within 5–8 days of symptom onset, in order to prevent a resurgent wave from overwhelming hospital capacity in the city. This estimate is robust to uncertainty in the effectiveness of the lockdown, as well as in immune protection against reinfection. To set these results in their economic context, we est...

Journal of Plankton Research, 2016

Highly intermittent spatial variability of phytoplankton is observed ubiquitously in marine ecosy... more Highly intermittent spatial variability of phytoplankton is observed ubiquitously in marine ecosystems, especially when measurements are performed at the micro-scale level. Therefore, theoretical developments and new modelling tools are required to understand the observed small-scale vertical structure and its relationship to ecosystem behaviour. Nearly all current ecosystem models are formulated entirely based on the mean field approximation, ignoring subgrid scale variability. Even if such approximation may be reasonable for meso-scales (and above), it cannot account for micro-scale dynamics, which may also impact macroscopic properties at the larger scale. To consider intermittency of variables in plankton ecosystem models, we apply a newly developed modelling approach called the closure approach. Detailed simulations were conducted, combining fluid-dynamics of the 1D water column with the nutrient-phytoplankton closure ecosystem model for application to a site in the northern North Sea. Compared with a control model, which does not account for such intermittency, the closure model produced substantially different spatio-temporal patterns of mean phytoplankton biomass and growth rate, which depended on the overall level of variability. In this study, we (i) seek to explore the effects of sub-scale variability coupled with physical transport and (ii) begin to address the yet unresolved question of how to consistently model the advection and diffusion of the variances and co-variances used to represent sub-scale variability in the closure approach. Our results suggest that it may be necessary to account explicitly for the intermittent distribution of plankton and nutrients, even in large-scale biogeochemical models.

Epidemiology, 2009

Background: Exposure to air pollutants has been related to preterm birth, but little evidence can... more Background: Exposure to air pollutants has been related to preterm birth, but little evidence can be available for PM 2.5 , O 3 and CO in China. This study aimed to investigate the short-term effect of exposure to air pollutants on risk preterm birth during 2014-2016 in Ningbo, China. Methods: We conducted a time-series study to evaluate the associations between daily preterm birth and major air pollutants (including PM 2.5 , PM 10 , SO 2 , NO 2 , O 3 and CO) in Ningbo during 2014-2016. A General Additive Model extend Poisson regression was used to evaluate the relationship between preterm birth and air pollution with adjustment for time-trend, meteorological factors and day of the week (DOW). We also conducted a subgroup analysis by season and age. Results: In this study, a total of 37,389 birth occurred between 2014 and 2016 from the Electronic Medical Records System of Ningbo Women and Children's Hospital, of which 5428 were verified as preterm birth. The single pollutant model suggested that lag effect of PM 2.5 , PM 10 , NO 2 reached a peak at day 3 before delivery and day 6 for SO 2 , and no relationships were observed for O 3 and preterm birth. Excess risks (95% confidence intervals) for an increase of IQR of air pollutant concentrations were 4.84 (95% CI: 1.77, 8.00) for PM 2.5 , 3.56 (95% CI: 0.07, 7.17) for PM 10 , 3.65 (95% CI: 0.86, 6.51) for SO 2 , 6.49 (95% CI: 1.86, 11.34) for NO 2 , − 0.90 (95% CI:-4.76, 3.11) for O 3 , and 3.36 (95% CI: 0.50, 6.30) for CO. Sensitivity analyses by exclusion of maternal age < 18 or > 35 years did not materially alter our results. Conclusions: This study indicates that short-term exposure to air pollutants (including PM 2.5 , PM 10 , SO 2 , NO 2) are positively associated with risk of preterm birth in Ningbo, China.

BMC Medicine, 2020

Background: The prevention of tuberculosis (TB) is key for accelerating current, slow declines in... more Background: The prevention of tuberculosis (TB) is key for accelerating current, slow declines in TB burden. The 2018 World Health Organization (WHO) guidelines on eligibility for preventive therapy to treat latent TB infection (LTBI) include people living with human immunodeficiency virus (PLHIV), household contacts of TB patients including children, and those with clinical conditions including silicosis, dialysis, transplantation, etc. and other country-specific groups. We aimed to estimate the potential impact of full implementation of these guidelines in the WHO SouthEast Asian (SEA) Region, which bears the largest burden of TB and LTBI amongst the WHO regions. Methods: We developed mathematical models of TB transmission dynamics, calibrated individually to each of the 11 countries in the region. We modelled preventive therapy in the absence of other TB interventions. As an alternative comparator, reflecting ongoing developments in TB control in the region, we also simulated improvements in the treatment cascade for active TB, including private sector engagement and intensified casefinding. Relative to both scenarios, for each country in the region, we projected TB cases and deaths averted between 2020 and 2030, by full uptake of preventive therapy, defined as comprehensive coverage amongst eligible populations as per WHO guidelines, and assuming outcomes consistent with clinical trials. We also performed sensitivity analysis to illustrate impact under less-than-optimal conditions. Results: At the regional level, full uptake of preventive therapy amongst identified risk groups would reduce annual incidence rates in 2030 by 8.30% (95% CrI 6.48-10.83) relative to 2015, in the absence of any additional interventions. If implemented against a backdrop of improved TB treatment cascades, preventive therapy would achieve an incremental 6.93 percentage points (95% CrI 5.81-8.51) of reduction in annual incidence rates, compared to 2015. At the regional level, the numbers of individuals with latent TB infection that need to be treated to avert 1 TB case is 64 (95% CrI 55-74). Sensitivity analysis illustrates that results for impact are roughly proportional to 'effective coverage' (the product of actual coverage and effectiveness of the regimen). Conclusions: Full implementation of WHO guidelines is important for ending TB in the SEA Region. Although future strategies will need to be expanded to the population level, to achieve large declines in TB incidence, the uptake of current tools can offer a valuable step in this direction.

BMJ Global Health, 2020

The Southeast Asia Region continues to battle tuberculosis (TB) as one of its most severe health ... more The Southeast Asia Region continues to battle tuberculosis (TB) as one of its most severe health and development challenges. Unless there is a substantial increase in investments for TB prevention, diagnosis, care and treatment, there will be catastrophic effects for the region. The uncontrolled TB burden impacts socioeconomic development and increase of drug resistance in the region. Based on epidemiological inputs from a mathematical model, a costing analysis estimates that the desired targets of ending TB are achievable with additional interventions, and critical thresholds require an increase in spending by almost double the current levels. The data source for financial allocation to TB programmes is the report submitted by countries to WHO, while projections are based on modelling. The model accounts for funding needs for all strategies based on published data and accounts for programme and patient costs. This paper delineates the resource needs, availability and gaps of ending...

Journal of Biological Dynamics, 2018

Global eradication of Guinea worm disease (GWD) is in the final stage but a mysterious epidemic o... more Global eradication of Guinea worm disease (GWD) is in the final stage but a mysterious epidemic of the parasite in dog population makes the elimination programme challenging. There is neither a vaccine nor an effective treatment against the disease and therefore intervention strategies rely on the current epidemiological understandings to control the spread of the disease. A novel mathematical model can predict the future outbreaks and it can quantify the dissemination rates of control interventions. Due to the lack of such novel models, a realistic mathematical model of GWD dynamics with human population, dog population, copepod population and the worm larvae is proposed and analyzed. Considering case data from Chad, we calibrate the model and perform global sensitivity analysis of the basic reproduction number with respect to the control parameters and copepod consumption rates. Furthermore, we investigate the impact of three control interventions: awareness of humans, isolation of infected dogs and copepod clearance from contaminated water sources. We also address the impact of combination interventions which leads to the conclusion that the combination of isolating the infected dogs and treating the contaminated ponds is a plausible way for eliminating the burden of GWD from Chad.

Objectives To investigate the impact of targeted vaccination strategies on morbidity and mortalit... more Objectives To investigate the impact of targeted vaccination strategies on morbidity and mortality due to COVID-19, as well as on the incidence of SARS-CoV-2, in India. Design Mathematical modelling. Settings Indian epidemic of COVID-19 and vulnerable population. Data sources Country specific and age-segregated pattern of social contact, case fatality rate and demographic data obtained from peer-reviewed literature and public domain. Model An age-structured dynamical model describing SARS-CoV-2 transmission in India incorporating uncertainty in natural history parameters was constructed. Interventions Comparison of different vaccine strategies by targeting priority groups such as key workers including health care professionals, individuals with comorbidities (24 - 60 year), and all above 60. Main outcome measures Incidence reduction and averted deaths in different scenarios, assuming that the current restrictions are fully lifted as vaccination is implemented. Results The priority g...

Frontiers in Marine Science

Previous modeling studies have shown that observed micro-scale (mm) variability of nutrients and ... more Previous modeling studies have shown that observed micro-scale (mm) variability of nutrients and phytoplankton biomass can strongly impact the large-scale mean growth response of phytoplankton in ways that cannot be represented by typical models based on the mean field approximation. Also, models accounting for the flexible eco-physiology of phytoplankton predict quite different responses to changing environmental conditions compared to most current (inflexible) models. Combining these two ideas for nutrient-phytoplankton systems we have developed a new "Flexible NP closure model" to represent competition among the three typically observed phytoplankton size classes: pico-, nano-, and micro-phytoplankton. Both micro-scale variability and flexible eco-physiology are expected to impact the competition among these size classes. With this work we begin to address how both these factors determine the size structure and size diversity of phytoplankton in the ocean. Under eutrophic conditions, variability does not impact the modeled growth rate of any size class. On the other hand, under oligotrophic conditions, variability preferentially enhances the biomass of the largest typically observed micro-size class, and reduces the biomass of the smallest nano-and intermediate pico-size classes.

India's lockdown against SARS-CoV-2, if lifted without any other mitigations in place, could ... more India's lockdown against SARS-CoV-2, if lifted without any other mitigations in place, could risk a second wave of infection. A test-and-isolate strategy, using PCR diagnostic tests, could help to minimise the impact of this second wave. Meanwhile, population-level serological surveillance can provide valuable insights into the level of immunity in the population. Using a mathematical model, consistent with an Indian megacity, we examined how seroprevalence data could guide a test-and-isolate strategy, for lifting a lockdown. For example, if seroprevalence is 20% of the population, we show that a testing strategy needs to identify symptomatic cases within 5 - 8 days of symptom onset, in order to prevent a resurgent wave from overwhelming hospital capacity in the city. This estimate is robust to uncertainty in the effectiveness of the lockdown, as well as in immune protection against reinfection. To set these results in their economic context, we estimate that the weekly cost of ...

Indian Journal of Medical Research

Nonlinear Analysis: Modelling and Control

This work deals with analytical investigation of local qualitative temporal behavior around inner... more This work deals with analytical investigation of local qualitative temporal behavior around inner equilibrium point of a model for three species food chain, studied earlier by Hastings and Powel and others. As an initial step towards the spectral analysis of the model, the governing equations have been split into linear and nonlinear parts around arbitrary equilibrium point. The explicit parameter dependence of eigenvalues of Jacobi matrix associated to the linear part have been derived. Analyzing these expressions in conjunction with some pedagogical analysis, a lot of predictions on stable, unstable or chaotic change of species have been highlighted. Agreement of predictions of this work with available numerical or semi-analytical studies suggest the utility of analytical results derived here for further investigation/analysis of the model as desired by earlier works.

Indian Journal of Medical Research

Journal of Theoretical Biology

BMC Medicine, 2017

Background: Against the backdrop of renewed efforts to control tuberculosis (TB) worldwide, there... more Background: Against the backdrop of renewed efforts to control tuberculosis (TB) worldwide, there is a need for improved methods to estimate the public health impact of TB programmes. Such methods should not only address the improved outcomes amongst those receiving care but should also account for the impact of TB services on reducing transmission. Methods: Vital registration data in India are not sufficiently reliable for estimates of TB mortality. As an alternative approach, we developed a mathematical model of TB transmission dynamics and mortality, capturing the scale-up of DOTS in India, through the rollout of the Revised National TB Control Programme (RNTCP). We used available data from the literature to calculate TB mortality hazards amongst untreated TB; amongst cases treated under RNTCP; and amongst cases treated under non-RNTCP conditions. Using a Bayesian evidence synthesis framework, we combined these data with current estimates for the TB burden in India to calibrate the transmission model. We simulated the national TB epidemic in the presence and absence of the DOTS programme, measuring lives saved as the difference in TB deaths between these scenarios. Results: From 1997 to 2016, India's RNTCP has saved 7.75 million lives (95% Bayesian credible interval 6.29-8.82 million). We estimate that 42% of this impact was due to the 'indirect' effects of the RNTCP in averting transmission as well as improving treatment outcomes. Conclusions: When expanding high-quality TB services, a substantial proportion of overall impact derives from preventive, as well as curative, benefits. Mathematical models, together with sufficient data, can be a helpful tool in estimating the true population impact of major disease control programmes.

The Lancet. Global health, Nov 5, 2016

The post-2015 End TB Strategy sets global targets of reducing tuberculosis incidence by 50% and m... more The post-2015 End TB Strategy sets global targets of reducing tuberculosis incidence by 50% and mortality by 75% by 2025. We aimed to assess resource requirements and cost-effectiveness of strategies to achieve these targets in China, India, and South Africa. We examined intervention scenarios developed in consultation with country stakeholders, which scaled up existing interventions to high but feasible coverage by 2025. Nine independent modelling groups collaborated to estimate policy outcomes, and we estimated the cost of each scenario by synthesising service use estimates, empirical cost data, and expert opinion on implementation strategies. We estimated health effects (ie, disability-adjusted life-years averted) and resource implications for 2016-35, including patient-incurred costs. To assess resource requirements and cost-effectiveness, we compared scenarios with a base case representing continued current practice. Incremental tuberculosis service costs differed by scenario a...

The Lancet. Global health, Nov 5, 2016

The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75%... more The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75% reduction in mortality from tuberculosis by 2025. We aimed to assess whether these targets are feasible in three high-burden countries with contrasting epidemiology and previous programmatic achievements. 11 independently developed mathematical models of tuberculosis transmission projected the epidemiological impact of currently available tuberculosis interventions for prevention, diagnosis, and treatment in China, India, and South Africa. Models were calibrated with data on tuberculosis incidence and mortality in 2012. Representatives from national tuberculosis programmes and the advocacy community provided distinct country-specific intervention scenarios, which included screening for symptoms, active case finding, and preventive therapy. Aggressive scale-up of any single intervention scenario could not achieve the post-2015 End TB Strategy targets in any country. However, the models p...

Preface v List of symbols vii List of abbreviations x Chapter 1 Introduction and Objectives Chapt... more Preface v List of symbols vii List of abbreviations x Chapter 1 Introduction and Objectives Chapter 2 Concept of Exergy and Ascendency 2.1 Introduction 2.2 Classical thermodynamics 2.3 Statistical thermodynamics 2.4 Concept of exergy 2.5 Concept of ascendency Chapter 3 Numerical aspects of modified Hastings and Powell model 3.1 3.5.1 Result of numerical evolution of Hastings and Powell model considering TPP 3.5.2 Conclusion Chapter 4 Linear stability analysis of nonlinear aquatic ecosystem model 4.1 Introduction CONTENTS iv 4.2 The mathematical model 4.3 Determination of equilibrium points 4.4 Hartman-Grobman theorem 4.5 Methodology of linear stability analysis around equilibrium points 4.6 Some terminology associated with fixed points 4.7 Behaviour of the aquatic ecosystem around equilibrium points 4.8 Conclusion Chapter 5 Center manifold reduction of Hastings and Powell model around non vanishing equilibrium point 5.1 Introduction 5.2 Center manifolds depending on parameters 5.3 Computation of center manifold 5.4 Example 5.5 Center manifold reduction of Hastings and Powell model around non vanishing equilibrium point 5.6 Result and Discussion Chapter 6 Conclusions and Future scopes 6.1 Conclusions 6.2 Future scopes Appendix A Eigen values of the matrix of the linear part of Hastings and Powell model for all parameters B Table presenting bifurcation points and its behavior for different parameter values References Preface vi Further, in this book, different mathematical techniques like spectral analysis, central manifold reduction, construction of Lyapunov coefficient and function have been used, to predict the analytic dependence of equilibrium points on parameters and to understand the change of their behaviours for variations of parameters which lead to switch over the model system in different states. Bifurcation analysis is also followed as a subject of classical mathematical origins. However the modern development of the subject followed with qualitative theory of differential equations pioneered by Poincaré. We are grateful to Elena Chercunova, Acquisition Editor of LAP Lambert Academic Publishing, Germany, for inviting us to write a book from our research area and her support and suggestion for doing this.

Indian Journal of Physics, 2004

ABSTRACT We review some calculations to demonstrate the basic properties of biological pattern fo... more ABSTRACT We review some calculations to demonstrate the basic properties of biological pattern formation obtained from some models. Assuming a shallow gradient of source distribution, one can show that a striking pattern of activator concentration may be obtained with a maximum at the terminal of high source density from three models viz. depletion model, activator-inhibitor model assuming common sources and that with different sources.

Ecology, 2015

Fishing is expected to alter the spatial heterogeneity of fishes. As an effective index to quanti... more Fishing is expected to alter the spatial heterogeneity of fishes. As an effective index to quantify spatial heterogeneity, the exponent b in Taylor&amp;amp;amp;amp;amp;amp;#39;s power law (V = aMb) measures how spatial variance (V) varies with changes in mean abundance (M) of a population, with larger b indicating higher spatial aggregation potential (i.e., more heterogeneity). Theory predicts b is related with life history traits, but empirical evidence is lacking. Using 50-yr spatiotemporal data from the California Current Ecosystem, we examined fishing and life history effects on Taylor&amp;amp;amp;amp;amp;amp;#39;s exponent by comparing spatial distributions of exploited and unexploited fishes living in the same environment. We found that unexploited species with smaller size and generation time exhibit larger b, supporting theoretical prediction. In contrast, this relationship in exploited species is much weaker, as the exponents of large exploited species were higher than unexploited species with similar traits. Our results suggest that fishing may increase spatial aggregation potential of a species, likely through degrading their size/age structure. Results of moving-window cross-correlation analyses on b vs. age structure indices (mean age and age evenness) for some exploited species corroborate our findings. Furthermore, through linking our findings to other fundamental ecological patterns (occupancy-abundance and size-abundance relationships), we provide theoretical arguments for the usefulness of monitoring the exponent b for management purposes. We propose that age/size-truncated species might have lower recovery rate in spatial occupancy, and the spatial variance-mass relationship of a species might be non-linear. Our findings provide theoretical basis explaining why fishery management strategy should be concerned with changes to the age and spatial structure of exploited fishes.