Evaluating seasonality of influenza in the tropics: Case study in Vietnam

评估热带地区流感的季节性：越南案例研究

• 批准号: 10385894
• 负责人: Joseph Servadio
• 金额: $ 6.68万
• 依托单位: PENNSYLVANIA STATE UNIVERSITY, THE
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10385894
• 关键词: Area; Behavior; Biological; Blood Circulation; COVID-19 vaccine; Calendar; Case Study; Cessation of life; Characteristics; Climate; Clinical; Country; Data; Disease Outbreaks; Epidemic; Epidemiology; Evaluation; Exhibits; Future; Holidays; Human; Immune; Immunity; Incidence; Infection; Influentials; Influenza; Influenza A virus; Influenza vaccination; Literature; Modeling; Pattern; Periodicity; Population; Population Heterogeneity; Predisposition; Productivity; Public Health; Recommendation; Recovery; Reporting; Reproduction; Research; Resource-limited setting; Resources; Respiratory Disease; Risk; Running; SARS-CoV-2 infection; Schools; Seasonal Variations; Seasons; Series; Structure; System; Testing; Time; United States; Update; Vaccination; Vietnam; Virus; Virus Diseases; Work; base; cross immunity; design; evidence base; experience; flu transmission; influenza epidemic; influenza surveillance; influenza virus strain; influenza virus vaccine; influenzavirus; mathematical model; public health intervention; respiratory virus; response; seasonal influenza; surveillance data; transmission process; trend; vaccination strategy; vaccine distribution

PROJECT SUMMARY Influenza is a persistent viral disease worldwide, with high case counts leading to deaths and losses in productivity yearly. In temperate regions of the world, such as the United States, influenza appears in annual wintertime cycles, with the influences of changing seasons creating predictable patterns of incidence, despite the fact that different subtypes and strains of the virus predominate during each season. In tropical regions, distinct seasonal patterns are not well established for influenza, suggesting that annual or climatic forces may not dictate transmission in these areas. The tropics include many resource-limited areas of the world where respiratory disease research is underfunded and influenza vaccination is not prioritized. Transmission patterns of influenza can be described through the use of mathematical models, which incorporate known biological mechanisms, such as infectivity, recovery, and duration of immunity following infection, in order to describe the dynamics, or population-level behaviors, of the virus. Models can incorporate cyclic patterns of influenza dynamics, which can include both seasonal cycles aligning with a calendar year as well as nonannual periodic cycles; models can also incorporate irregular epidemics, though this is more challenging to model and less commonly seen in current literature. Irregular epidemics can be viewed as “regime switches,” which describes transitions between endemic time periods with consistently low incidence and epidemic time periods with short periods of elevated incidence. This study aims to investigate potentially cyclic or acyclic dynamics of influenza in the tropics, using Vietnam as a case study. The first aim seeks to define patterns describing cyclic or acyclic dynamics and then use a mathematical model to show under what conditions acyclic dynamics can exist. Influenza characteristics that could allow acyclic dynamics potentially include duration of immunity following infection, cross-immunity, and population structure. The second aim seeks to use the developed model as well as influenza data from Vietnam to determine whether influenza dynamics follow cyclic or acyclic patterns. Comparing these results to identical analyses using data from temperate regions influenza data will allow us to compare the strength of annual cycles between tropical and temperate regions. The third aim seeks to identify characteristics of influenza virus, population patterns, or external factors that may be able to explain the cyclic or acyclic patterns observed in influenza dynamics in Vietnam. This will show what characteristics of influenza or external factors provide the strongest predictions of future influenza incidence in Vietnam. Uses of the study results include better informed and appropriately-timed vaccination strategies for influenza in Vietnam. The main points of novelty in this study lie in the explicit testing for cyclic or acyclic patterns in the tropics, which is less commonly investigated, and a mechanistic modeling approach to identify the potential causes of non- annual behavior of influenza transmission in the tropics.

项目摘要 流感是全球持续性病毒疾病 每年生产力。在世界的温度区域，例如美国，影响年度的影响 冬季周期，随着季节变化的影响创造了可预测的事件模式，目的地 病毒的不同亚型和菌株在每个季节中占主导地位。在热带地区， 影响力的不同季节性模式并没有很好地确定，这表明年度或气候力量可能 不决定这些区域的传播。热带地区包括世界上许多资源有限的地区 呼吸系统疾病研究资金不足，并且没有优先考虑影响疫苗。传输模式 可以通过使用数学模型来描述造成影响力 感染后感染，恢复和免疫力的机制，以描述 病毒的动态或人群水平行为。模型可以融合影响力的循环模式 动力学，可以包括季节性周期与日历年的一致以及非年期的周期性 周期；模型还可以结合不规则的情节，尽管这对模型而言更为挑战，更少 通常在当前文献中看到。不规则的情节可以看作是“政权开关”，它描述了 内在时间段之间的过渡，持续的低入射和流行时间时间很短 升高事件的时期。这项研究旨在研究影响力的潜在循环或环状动力学 在热带地区，使用越南作为案例研究。第一个目的旨在定义描述循环或无环的模式 动力学，然后使用数学模型在哪些条件下可以显示无环动力学。 流感特征可能允许无环动态可能包括免疫持续时间之后 感染，跨免疫力和人口结构。第二个目标也试图使用开发的模型 作为来自越南的影响力数据，以确定影响力动态是否遵循环状或无环模式。 将这些结果与使用来自温度区域的数据影响的相同分析进行比较，将使我们能够 比较热带和温度区域之间的年度周期的强度。第三个目标试图确定 可能能够解释循环的流感病毒，种群模式或外部因素的特征 或在越南的影响力动力学中观察到的无环模式。这将显示出造成影响的哪些特征 或外部因素提供了对越南未来影响的有力预测。研究的用途 结果包括越南有影响力的更好的知情和适当定时的疫苗接种策略。这 这项研究的新颖性主要点在于对热带地区环状或环状模式的明确测试， 不太常见的研究和一种机械建模方法来确定非 - 热带影响力的年度影响。