Health Policy Development Research Articles

A novel low sampling rate and cost-efficient active sampler for medium/long-term monitoring of gaseous pollutants

Active sampling is a dependable approach for gaseous pollutants monitoring, offering high accuracy and precision that is unaffected by environmental factors such as wind and temperature in comparison to passive sampling. To measure long-term average concentrations while minimizing the use of materials, a reduced sampling rate is necessary. Thus, this study aims to develop a novel low sampling rate (down to 1 mL/min) and cost-efficient active sampler (LASP) for medium/long-term monitoring of gaseous pollutants. The LASP mainly consisted of a syringe pump, a Y-shaped fitting with two one-way valves, and a control unit for intermittent operation. Results showed that LASP can obtain a sampling rate of less than 1 mL/min and sampling rate exhibited a high level of stability. Daily average concentrations measurements for nitrogen dioxide and formaldehyde by LASP had normalized mean biases of 2.8% and 5.2%, respectively. These numbers were − 5.8% and 6.1% for weekly-average samplings. This study demonstrated applications of LASP in real outdoor (daily-average) and indoor (weekly-average) air quality measurements. It worked well with low noise levels, and without interfering with occupants' daily activities. LASP can assist in improving our ability to monitor air quality and pollutants emissions, thereby supporting health research and policy development. Environmental implicationGaseous air pollution is an important hazardous factor threatening human health. Medium/long-term air quality monitoring is essential for outdoor and indoor air quality assessment and control. However, air sampler for medium/long-term sampling is lacking. This study developed a novel low sampling rate and cost-efficient active sampler and applied it to medium/long-term air sampling. The sampler can work at a sampling rate of less than 1 mL/min. This technology provides a feasible strategy for medium/long-term monitoring of gaseous air pollutants in both environments and emission hotspots.

International Importation Risk Estimation of SARS-CoV-2 Omicron Variant with Incomplete Mobility Data

A novel Omicron subvariant named BQ.1 emerged in Nigeria in July 2022 and has since become a dominant strain, causing a significant number of repeated infections even in countries with high-vaccination rates. Due to the high flow of people between Western Africa and other non-African countries, there is a high risk of Omicron BQ.1 being introduced to other countries from Western Africa. In this context, we developed a model based on deep neural networks to estimate the probability that the Omicron BQ.1 introduced to other countries from Western Africa based on the incomplete population mobility data from Western Africa to other non-African countries. Our study found that the highest risk was in France and Spain during the study period, while the importation risk of other 13 non-African countries including Canada and the United States is also high. Our approach sheds light on how deep learning techniques can assist in the development of public health policies, and it has the potential to be extended to other types of viruses.

RETRACTED ARTICLE: Percolation Analysis of COVID-19 Epidemic

AbstractThe spread of COVID-19 can be greatly influenced by human mobility. However, implementing control measures based on restrictions can be costly. That is why it is crucial to develop a quarantine strategy that can minimize the spread of the disease while also reducing costs. This article focuses on determining the percolation threshold of COVID-19 in Tehran province using a square lattice and two types of city connections. The study identifies the number of roads that need to be closed and the cities that should be quarantined. Monte Carlo simulations using the Newman and Ziff and Union-Find algorithms were conducted through the $$\text {SEAIRD}$$ SEAIRD model to assess the effectiveness of the proposed measures. The results showed a possible reduction of 81$$\%$$ % in disease spread. This approach can be used in other regions to assist in the development of public health policies.

Biopharmaceutical Companies: The Winner of the Stock Market During the Covid Period

Developing a so-called "green economy" garners more support in the current climate of uncertainty and danger. Since the beginning of the 21st century, we have recognized that the drive to develop the economy causes irreparable harm to the planet's ecosystem. After the Covid pandemic, a new intermediate industry, the biopharmaceutical industry, has emerged to reduce the tension between the human ecology and the earth's ecosystem. This industry devised a successful response to the health, economic, and social issues of the pandemic age. This paper aims to examine the financial performance of two renowned biopharmaceutical companies, Pfizer and Moderna, which have been permitted to distribute the mRNA vaccine worldwide. This paper concludes the investigation into the stock performance of these two companies prior to and throughout COVID. Besides, examination of the technology market index, market volatility, and investor sentiment reveals the various fluctuations. In addition, the data reveals an effect of contagion between the two enterprises and the technology market. Thus, the research gives useful information for the development of public health economics, policy, and administration.

Health Professionals’ Role in Promoting Health and Environmental Sustainability through Sustainable Food Advocacy: A Systematic Literature Review

The relationship between health, environmental sustainability, and food systems has garnered increasing attention, emphasizing the crucial role of healthcare professionals in advocating for sustainable food practices. This systematic literature review aimed to examine their role in promoting health and environmental sustainability through sustainable food advocacy. Following a systematic and rigorous methodology, eligible articles published in English within the past five years were searched and screened, resulting in a total of five articles for further analysis. The review revealed the fragmented debate on food security and sustainability, emphasizing the need for sustainable food systems to address various challenges. Specific actions identified include reducing plate waste in hospitals, implementing sustainable food sourcing strategies in healthcare to mitigate the climate footprint, and promoting sustainable nutrition. The findings underscore the importance of education, community engagement, governance, and a systemic approach in driving positive change regarding nutrition, health, and sustainability. This review offers important perspectives for healthcare practice, allied health educational programs, research, and public health policy development. It highlights the importance of healthcare professionals in advocating for sustainable food practices, which play a critical role in improving health outcomes and reducing environmental impacts.

Infectious diseases prevention policies, strategies and measures: Literature review

<b>Introduction:</b> Throughout the history, infectious diseases have been the most serious cause of morbidity and mortality of the population worldwide, as over the years there have been–and with the development of human activities–many significant outbreaks of infectious diseases. The threats they pose, including their resistance to antibiotics, make the review and development of public health policies a major issue.<br /> <b>Aim:</b> The main purpose of this article is to present most recent policies and strategies on infectious diseases prevention via a literature review and highlight the necessity of developing a holistic approach to the formulation of infectious diseases prevention policies. Moreover, through the most recent literature on this topic it is observed that there is a need to draw up innovative policies, to defend public health and enforce the one health.<br /> <b>Methodology: </b>For this literature review, a research in PubMed database and official organization was conducted and thus a total number (n=28) of articles and handbooks was collected. From PubMed database n<sub>1</sub>=15 articles were extracted while from websites of official organizations n<sub>2</sub>=13 was extracted. The final number of references that have been used for this paper was n=33 and were managed by using ZOTERO software.<br /> <b>Conclusion:</b> It is clearly observed that collective work for prevent, and control infectious diseases is mandatory. Also, there is a need for strengthen the already existed public health systems, in order to be well-prepared. A major public health tool is communication, it is very important to communicate strategies and policies to individuals in a proper and comprehensive way.

Do refugees with better mental health better integrate? Evidence from the Building a New Life in Australia longitudinal survey.

Hardly any evidence exists on the effects of mental distress on refugee labor outcomes. We offer the first study on this topic in the context of Australia, one of the host countries with the largest number of refugees per capita in the world. Analyzing the Building a New Life in Australia longitudinal survey, we exploit the variations in traumatic experiences of refugees interacted with post-resettlement time periods to causally identify the impacts of refugee mental health. We find that worse mental health, as measured by a one-standard-deviation increase in the Kessler mental health score, reduces the probability of employment by 11.9% and labor income by 22.8%. These effects appear more pronounced for refugees that newly arrive or are without social networks, but they may be ameliorated with government support. These findings have significant implications for the development of health and labor policies, particularly regarding the integration of refugees within host countries.

SARS-CoV-2 omicron spike simulations: broad antibody escape, weakened ACE2 binding, and modest furin cleavage.

The recent emergence of the omicron variant of the SARS-CoV-2 virus with large numbers of mutations has raised concern about a potential new surge in infections. Here we use molecular dynamics to study the biophysics of the interface of the BA1 and BA2 omicron spike protein binding to (i) the ACE2 receptor protein, (ii) antibodies from all known binding regions, and (iii) the furin binding domain. Our simulations suggest that while there is a significant reduction of antibody (Ab) binding strength corresponding to escape, the omicron spikes pay a cost in terms of weaker receptor binding as measured by interfacial hydrogen bonds (H-bond). The furin cleavage domain (FCD) is the same or weaker binding than the delta variant, suggesting lower fusogenicity resulting in less viral load and disease intensity than the delta variant. IMPORTANCE The BA1 and BA2 and closely related BA2.12.2 and BA.5 omicron variants of SARS-CoV-2 dominate the current global infection landscape. Given the high number of mutations, particularly those which will lead to antibody escape, it is important to establish accurate methods that can guide developing health policy responses that identify at a fundamental level whether omicron and its variants are more threatening than its predecessors, especially delta. The importance of our work is to demonstrate that simple in silico simulations can predict biochemical binding details of the omicron spike protein that have epidemiological consequences, especially for binding to the cells and for fusing the viral membrane with the cells. In each case, we predicted weaker binding of the omicron spike, which agreed with subsequent experimental results. Future virology experiments will be needed to test these predictions further.

Managing food allergies at school: A qualitative study

IntroductionThe prevalence of childhood allergic diseases, including food allergies, has increased globally. Parents and children have experienced psychosocial and financial difficulties, decreased quality of life, anxiety, and depression in the management of food allergies in schools. PurposeThe aim of the study was to determine the challenges experienced by mothers of children with food allergies during their children's school life. DesignA qualitative phenomenological study design was used. MethodsOnline interviews were conducted with 9 mothers who have children with food allergies between June–August 2022. The data were analyzed using the content analysis method. The COREQ checklist was used in the study. ResultsThe ages of the mothers participating in the study ranged from 28 to 40. Four themes were generated from 75 codes: 1) Problems experienced in the process of utilizing health services, 2) Burden of care, 3) Coming out of the shell: The school process, and 4) Environmental and social perspective. ConclusionsMothers carried the burden of food allergy management during the school process, and the increased burden of care negatively impacted mothers emotionally, physically, and socially. Also, mothers were anxious about the safety of their school-age children with food allergies and their experiences with school administration, teachers, and other parents made it difficult for food allergy management in the school environment. Clinical relevanceChildren with chronic health problems such as food allergies need to be closely monitored by a health professional in school to ensure their safety. Nurses have a pivotal role in supporting families to address their child's food allergies competently, hence fostering positive health outcomes. This study showed that there was a need for the development of school health policies to ensure the safety of children with food allergies and to reduce anxiety and care burden among mothers.

Lifestyle Medicine Interventions to Manage Hypertension in Brazilian Patients With Type 2 Diabetes

Hypertension and type 2 Diabetes (T2D) are highly associated and can promote an additive risk of mortality and hospitalization, as well as a significant burden on the Brazilian Unified Healthcare System. Despite this, blood pressure and glycemic control are still suboptimal and remain a significant challenge in Brazil. As it will be reviewed in this paper, current evidence supports the effectiveness of various dietary, exercise, and lifestyle interventions for hypertension and T2D. Among dietary interventions, the DASH diet appears to be particularly effective in reducing blood pressure and decreasing the risk of cardiovascular mortality, with a moderate effect on glycemic control. Regular physical activity, including aerobic, resistance, or combined exercise programs, is also recommended to reduce blood pressure, improve glycemic control and also reduce cardiovascular disease risk. Stress reduction programs have also been shown to be effective in reducing blood pressure. However, although numerous lifestyle interventions are effective for hypertension and T2D, factors such as personal preferences, motivation, and cultural background should be considered to ensure the long-term sustainability of these interventions. In addition, there is a need for further research to determine the cost-effectiveness of lifestyle interventions in the Brazilian population to encourage the development of evidence-based health policies.

Evidence of interactive effects of late-pregnancy exposure to air pollution and extreme temperature on preterm birth in China: a nationwide study

Perinatal exposure to heat and air pollution has been shown to affect the risk of preterm birth (PTB). However, limited evidence exists regarding their joint effects, particularly in heavily polluted regions like China. This study utilized data from the ongoing China Birth Cohort Study, including 103 040 birth records up to December 2020, and hourly measurements of air pollution (PM2.5, NO2, and O3) and temperature. We assessed the nonlinear associations between air pollution and temperature extereme exposures and PTB by employing generalized additive models with restricted cubic slines. Air pollution and temperature thresholds (corresponding to minimum PTB risks) were determined by the lowest Akaike Information Criterion. We found that maternal exposures to PM2.5, NO2, O3, and both low and high temperature during the third trimester of pregnancy were independently associated with increased risk of PTB. The adjusted risk ratios for PTB of PM2.5, O3, NO2, and temperature at the 95th percentile against thresholds were 1.32 (95% CI: 1.23, 1.42), 1.33 (95% CI: 1.18, 1.50), 1.44 (95% CI: 1.33, 1.56) and 1.70 (95% CI: 1.56, 1.85), respectively. Positive additive interactions [relative excess risk due to interaction (RERI) > 0] of PM2.5–high temperature (HT), O3–HT, O3–low temperature (LT) are identified, but the interactive effects of PM2.5 and LT were negative (RERI < 0). These observed independent effects of air pollution and temperature, along with their potential joint effects, have important implications for future studies and the development of public health policies aimed at improving perinatal health outcomes.

Diabetes mellitus, its prevalence, awareness, and control in Panama: Data from ENSPA 2019, a national cross-sectional study.

Diabetes mellitus (DM) represents an important global burden of disease. In Panama, DM was investigated in 1 study utilizing questionnaires and in another using biomarkers, but at subnational level. Using data from a recent cross-sectional country-wide population-based study that included biomarkers, we estimated the prevalence of DM, its awareness, and control; evaluating possible risk factors. We used data from 4400 participants aged 18 years or older from the National Health Study of Panama (ENSPA) study conducted in 2019 at a national level. Weighted prevalence and 95% confidence intervals for DM, awareness, and control were estimated by sociodemographic factors, family history of DM, tobacco and alcohol use, nutritional status, and hypertension. Odds ratios (ORs) and 95% confidence intervals were calculated using logistic regression models to assess the possible risk factors associated with DM prevalence and awareness. We generated OR estimates by pooling ENSPA data with a previous regional study, prevalence of cardiovascular risk factors. The prevalence of DM was estimated to be 12.4% (10.9%-14.05%). In both men and women, age, family history of diabetes (OR in men: 4.0 ([2.4-6.7]; OR in women 3.5 [2.5-4.8]), and obesity (OR in men: 2.6 [1.4-5.1]; OR in women: 2.0 [0.9-4.5]) were associated with DM. Diagnosed and controlled hypertension was associated with DM only in women (OR: 2.1 [1.2-3.6]). DM awareness was estimated to be 62.6% (56.3%-68.9%). In both men and women, DM awareness was associated with age and a family history of diabetes (OR in men: 6.6 [2.4-18.4]; OR in women 1.9 ([1.1-3.6]). In women, having secondary education (OR: 1.9 [0.9-3.9]) and being diagnosed with uncontrolled hypertension (OR: 3.3 [1.2-9.5]) was also associated to DM awareness. Men in the ENSPA study were less likely to be aware of DM than those in the prevalence of cardiovascular risk factors (OR: 0.2 [0.0-0.7]). Less than half of the individuals diagnosed with DM had their condition controlled (39.6% [31.4%-47.8%]). This study revealed that the prevalence, awareness, and control of DM were similar to recent estimates reported in other Latin American countries. It also provides a baseline regarding DM and associated risk factors in Panama at a country-level knowledge that is essential for health policy development and useful in clinical practice.

A study on the representation of mental disorders in Turkish newspapers

Background Newspapers that address mental disorders affect health care positively or negatively and can affect the public’s perspective with the way they explain mental disorders. Aims To examine the representation of news about mental disorders published in Turkish newspapers. Methods Using the document analysis method, 230 news about mental disorders published in the six most read newspapers in 2022 were examined. Results It has been concluded that the descriptive characteristics of individuals with mental disorders are often stated, schizophrenia and psychotic disorders are mentioned most, mental disorders are associated with delinquency and violent behaviour, these people are mostly represented by being detained as a result of the events, and negative concepts are frequently used in newspaper reports. Five sub-themes were determined under the main theme of “Negative Concepts”: “Exaggerated Discourses”, “Stigmatizing Discourses”, “Discourses Targeting Mental Health”, “Discourses That May Cause Negative Emotions”, “Discourses Containing Misdescription”. Conclusions Newspaper items about mental disorders are represented as stigmatizing and misleading by using negative concepts. The sensitivity of media workers, the development of mental health policies and cooperation with mental health workers contribute to the recovery process of individuals with mental disorders.

The impact of dietary fructose on gut permeability, microbiota, abdominal adiposity, insulin signaling and reproductive function

The excessive intake of fructose in the regular human diet could be related to global increases in metabolic disorders. Sugar-sweetened soft drinks, mostly consumed by children, adolescents, and young adults, are the main source of added fructose. Dietary high-fructose can increase intestinal permeability and circulatory endotoxin by changing the gut barrier function and microbial composition. Excess fructose transports to the liver and then triggers inflammation as well as de novo lipogenesis leading to hepatic steatosis. Fructose also induces fat deposition in adipose tissue by stimulating the expression of lipogenic genes, thus causing abdominal adiposity. Activation of the inflammatory pathway by fructose in target tissues is thought to contribute to the suppression of the insulin signaling pathway producing systemic insulin resistance. Moreover, there is some evidence that high intake of fructose negatively affects both male and female reproductive systems and may lead to infertility. This review addresses dietary high-fructose-induced deteriorations that are obvious, especially in gut permeability, microbiota, abdominal fat accumulation, insulin signaling, and reproductive function. The recognition of the detrimental effects of fructose and the development of relevant new public health policies are necessary in order to prevent diet-related metabolic disorders.

Effect of Excessive Use of Digital Devices on the Vision of Growing Children Between 5-20 Years of Age

Background: The widespread use of digital devices among children has raised concerns about the potential adverse effects on their vision. This study aimed to investigate the impact of digital devices on the vision of growing children in Bangladesh, focusing on the prevalence of various vision problems and the effect of a -0.50 D Spherical Concave Lens on these issues. Material &amp; Methods: This cross-sectional study was conducted in a private chamber of Dhaka, Bangladesh, over 16 months (March 2021-July 2022). A total of 428 children aged 5-20 years were selected, and data was collected using a structured questionnaire through in-person interviews with participants and their legal guardians. Informed consent and ethical approval were obtained. Data analysis was conducted using SPSS V.25 software. Results: The study found a high prevalence of myopia (26.87%), asthenopia (10%), eye strain (8%), and mild astigmatism (5%) among the participants. Autorefraction measurements ranged from -2.00D to -10.00 Diopters, with minimal final correction required. The use of a -0.50 D Spherical Concave Lens demonstrated significant improvements in asthenopia, eye strain, and mild astigmatism. Conclusion: Our findings highlight the adverse effects of digital devices on the vision of growing children and the potential benefits of interventions, such as the use of a -0.50 D Spherical Concave Lens, in alleviating these issues. Further research and the development of public health policies and educational programs are needed to promote eye health and reduce the adverse effects of digital device use on children’s vision.

Prioritizing population oral health through public policy in Australia: the Victorian experience.

Dental caries, a non-communicable disease, is one of the most prevalent diseases globally and share common modifiable risk factors with obesity such as excess sugar intake. However, prioritization by governments to improve population oral health has been limited and is typically excluded from the discourse of public health policy development. Therefore, interventions that target dental caries can have other co-benefits including obesity prevention. In Victoria, Australia, local government authorities have a regulatory requirement to develop their Municipal Health and Wellbeing Plans. The aim of this paper is to identify whether prioritization for oral health by local government authorities in Victoria has changed through the subsequent renewal of the Victorian Public Health and Wellbeing Plans 2011-2015 and 2019-2023. Three desktop audits for all publicly available Municipal Health and Wellbeing Plans by local government authorities in Victoria were conducted between 2014 and 2022. Key terms related to oral health was searched within these policy documents and categorized into six indicators: (i) included oral health as a priority, (ii) linked healthy eating and oral health, (iii) supported the Achievement Program, (iv) included the Smiles 4 Miles program, (v) advocated for fluoridated drinking water, and (vi) included other strategies related to oral health. Overall, there was statistically significant reduction in five of the six indicators, with the exception for prioritization of other strategies related to oral health such as targeting excess sugar intake and smoking. A multi-sectoral approach, that includes oral health would be advantageous to address the growing burden of non-communicable diseases.

What Are We Talking About When We Talk About Palliative Care in Heart Failure?

Background: Heart failure is a chronic, complex and progressive disease, with high morbidity and mortality, and growing prevalence. Despite advances in therapeutic strategies to improve survival and reduce hospitalizations, heart failure still generates a negative impact on the patients’ quality of life, making it necessary to develop health policies based not only on their physical but also on their psychosocial integrity. Palliative care refers to specialized, interdisciplinary care focused on improving the quality of life of patients who suffer a disease with elevated morbidity and mortality. The aim of this review is to assess the impact of the implementation of palliative care in the multidisciplinary treatment of heart failure throughout all the stages of the disease, and to determine the feasibility of its application in clinical practice.

Risk Factors of Transfusion Transmissible Infections among Blood Donors at Karongi Regional Centre for Blood Transfusion in Rwanda

BackgroundBlood transfusion saves human lives, but also it can be a route for Transfusion-Transmissible Infections (TTIs) including Human Immuno-Deficiency Virus (HIV), Hepatitis B virus (HBV), Hepatitis C virus (HCV), and syphilis.ObjectiveThis study aimed to explore the risk factors associated with TTIs among blood donors at Regional Centre for Blood Transfusion (RCBT) of Karongi, Rwanda.MethodsThis was a retrospective cross-sectional study design conducted among 36,708 blood donors from 2015 to 2019. Data were extracted from the system known as eProgesaused and the outcome variable were TTIs including HBV, HCV and HIV (measured using Enzyme Immuno-Assay/Chemiluminescence Immunoassay) and syphilis (determined by Rapid Reagin Plasma). Descriptive statistics was computed to describe the characteristics of the blood donors. Bivariate and multivariable logistic regression were performed to assess the risk factors associated with TTIs. P value less than 0.05 was considered statistically significant.ResultsThe study found that the overall prevalence of TTIs was 2.1%, while the prevalences of HBV, HCV, HIV, and syphilis were 1.3%, 0.4%, 0.06%, and 0.34%, respectively. Multivariable analysis showed that the factors associated with HBV, HCV, HIV and syphilis were being male, age more than 25 years, being married, living in urban areas, first time blood donors and blood donors living in Rusizi, Rusizi, Nyamasheke and Karongi districts.ConclusionThis study revealed that the most frequent TTI was HBV among blood donors and the main risk groups were males, age group of 26-35 years, married and first time donors. Hence, while developing health policies to reduce the effects of HBV infection on safe blood transfusion, these study findings should be taken into account.&#x0D; Rwanda J Med Health Sci 2023;6(2):143-153

'An extra fight I didn't ask for': A qualitative survey exploring the impact of calories on menus for people with experience of eating disorders.

The UK government made it mandatory for large restaurants and cafes in England to display calorie labels on menus. Existing evidence identifies minimal potential for benefit, but significant potential for harm to those with eating disorders. To date, only one published study has directly explored the impact of this legislation on those with eating disorders. This study explores the impact of calorie labelling on menus on adults with experience of eating disorders in England. A qualitative online survey was designed and distributed, and 399 adults with current or past experience/s of eating disorders completed the survey. Reflexive thematic analysis was used, informed by a critical realist approach. Six themes were developed: (1) impacts on relationships, (2) exclusion and increased isolation, (3) restricted freedom, (4) dis/embodiment, (5) anger and frustration at the perpetuation of diet culture and (6) we are all responsible for ourselves. Most participants felt calorie labels on menus is detrimental to their eating disorder and/or recovery. People are navigating multiple opposing cultural narratives around health, bodies and eating disorder recovery that can put additional barriers in place to developing a relationship with food and body that they would like. Calorie labelling on menus is likely to adversely impact those with eating disorders. Menus with calories should be available separately but should not be the first or only one provided. People with experience of eating disorders should be directly involved in the development of public health legislation and policy that is likely to affect them.

Prevention and control of mosquito-borne diseases across Toronto and Brasília: A document-based descriptive analysis

The present study analyzed documents by health departments in Toronto, Ontario, Canada and Brasília, Federal District, Brazil that address strategies for prevention and control of mosquito-borne diseases (MBDs) between 2012 and 2022. Nineteen documents were fully read and analyzed. Results suggest both Toronto and Brasília base their strategies on Integrated Vector Management, performing entomological, environmental, vector and epidemiological surveillance; source reduction; public education and mobilization; and chemical control as an ultimate resource. In addition, results indicate many documents lacked references lists with scientific evidence, although the most recent ones usually follow international protocols and national experiments results. Most do not teach workers on how to verify the effectiveness of the executed measures. Further research investigating people’s perceptions and behaviors towards MBDs can provide a more solid ground for effective health policy development, especially in cases of major public health concern, such as dengue and other neglected tropical diseases epidemics.