Last data update: Apr 29, 2024. (Total: 46658 publications since 2009)
Records 1-6 (of 6 Records) |
Query Trace: Chen YH[original query] |
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Estimating the HIV Effective Reproduction Number in the United States and Evaluating HIV Elimination Strategies
Chen YH , Farnham PG , Hicks KA , Sansom SL . J Public Health Manag Pract 2021 28 (2) 152-161 CONTEXT: The reproduction number is a fundamental epidemiologic concept used to assess the potential spread of infectious diseases and whether they can be eliminated. OBJECTIVE: We estimated the 2017 United States HIV effective reproduction number, Re, the average number of secondary infections from an infected person in a partially infected population. We analyzed the potential effects on Re of interventions aimed at improving patient flow rates along different stages of the HIV care continuum. We also examined these effects by individual transmission groups. DESIGN: We used the HIV Optimization and Prevention Economics (HOPE) model, a compartmental model of disease progression and transmission, and the next-generation matrix method to estimate Re. We then projected the impact of changes in HIV continuum-of-care interventions on the continuum-of-care flow rates and the estimated Re in 2020. SETTING: United States. PARTICIPANTS: The HOPE model simulated the sexually active US population and persons who inject drugs, aged 13 to 64 years, which was stratified into 195 subpopulations by transmission group, sex, race/ethnicity, age, male circumcision status, and HIV risk level. MAIN OUTCOME MEASURES: The estimated value of Re in 2017 and changes in Re in 2020 from interventions affecting the continuum-of-care flow rates. RESULTS: Our estimated HIV Re in 2017 was 0.92 [0.82, 0.94] (base case [min, max across calibration sets]). Among the interventions considered, the most effective way to reduce Re substantially below 1.0 in 2020 was to maintain viral suppression among those receiving HIV treatment. The greatest impact on Re resulted from changing the flow rates for men who have sex with men (MSM). CONCLUSIONS: Our results suggest that current prevention and treatment efforts may not be sufficient to move the country toward HIV elimination. Reducing Re to substantially below 1.0 may be achieved by an ongoing focus on early diagnosis, linkage to care, and sustained viral suppression especially for MSM. |
Using video-analysis technology to estimate social mixing and simulate influenza transmission at a mass gathering
Rainey JJ , Koch DB , Chen YH , Yuan J , Cheriyadat A . Epidemics 2021 36 100466 Mass gatherings create settings conducive to infectious disease transmission. Empirical data to model infectious disease transmission at mass gatherings are limited. Video-analysis technology could be used to generate data on social mixing patterns needed for simulating influenza transmission at mass gatherings. We analyzed short video recordings of persons attending the GameFest event at a university in Troy, New York, in April 2013 to demonstrate the feasibility of this approach. Attendees were identified and tracked during three randomly selected time periods using an object-tracking algorithm. Tracks were analyzed to calculate the number and duration of unique pairwise contacts. A contact occurred each time two attendees were within 2 m of each other. We built and tested an agent-based stochastic influenza simulation model assuming two scenarios of mixing patterns in a geospatially accurate representation of the event venue -one calibrated to the mean cumulative contact duration estimated from GameFest video recordings and the other using a uniform mixing pattern. We compared one-hour attack rates (i.e., becoming infected) generated from these two scenarios following the introduction of a single infectious seed. Across the video recordings, 278 attendees were identified and tracked, resulting in 1,247 unique pairwise contacts with a cumulative mean contact duration of 74.76 s (SD: 80.71). The one-hour simulated mean attack rates were 2.17 % (95 % CI:1.45 - 2.82) and 0.21 % (95 % CI: 0.14 - 0.28) in the calibrated and uniform mixing model scenarios, respectively. We simulated influenza transmission at the GameFest event using social mixing data objectively captured through video-analysis technology. Microlevel geospatially accurate simulations can be used to assess the layout of event venues on social mixing and disease transmission. Future work can expand on this demonstration project to larger spatial and temporal scenes in more diverse settings. |
Progression and transmission of HIV (PATH 4.0)-A new agent-based evolving network simulation for modeling HIV transmission clusters.
Singh S , France AM , Chen YH , Farnham PG , Oster AM , Gopalappa C . Math Biosci Eng 2021 18 (3) 2150-2181 We present the Progression and Transmission of HIV (PATH 4.0), a simulation tool for analyses of cluster detection and intervention strategies. Molecular clusters are groups of HIV infections that are genetically similar, indicating rapid HIV transmission where HIV prevention resources are needed to improve health outcomes and prevent new infections. PATH 4.0 was constructed using a newly developed agent-based evolving network modeling (ABENM) technique and evolving contact network algorithm (ECNA) for generating scale-free networks. ABENM and ECNA were developed to facilitate simulation of transmission networks for low-prevalence diseases, such as HIV, which creates computational challenges for current network simulation techniques. Simulating transmission networks is essential for studying network dynamics, including clusters. We validated PATH 4.0 by comparing simulated projections of HIV diagnoses with estimates from the National HIV Surveillance System (NHSS) for 2010-2017. We also applied a cluster generation algorithm to PATH 4.0 to estimate cluster features, including the distribution of persons with diagnosed HIV infection by cluster status and size and the size distribution of clusters. Simulated features matched well with NHSS estimates, which used molecular methods to detect clusters among HIV nucleotide sequences of persons with HIV diagnosed during 2015-2017. Cluster detection and response is a component of the U.S. Ending the HIV Epidemic strategy. While surveillance is critical for detecting clusters, a model in conjunction with surveillance can allow us to refine cluster detection methods, understand factors associated with cluster growth, and assess interventions to inform effective response strategies. As surveillance data are only available for cases that are diagnosed and reported, a model is a critical tool to understand the true size of clusters and assess key questions, such as the relative contributions of clusters to onward transmissions. We believe PATH 4.0 is the first modeling tool available to assess cluster detection and response at the national-level and could help inform the national strategic plan. © 2021 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) |
Combinations of interventions to achieve a national HIV incidence reduction goal: insights from the agent-based PATH 2.0 model
Gopalappa C , Sansom SL , Farnham PG , Chen YH . AIDS 2017 31 (18) 2533-2539 OBJECTIVE: Analyzing HIV care service targets for achieving a national goal of a 25% reduction in annual HIV incidence and evaluating the use of annual HIV diagnoses to measure progress in incidence reduction. DESIGN: Because there are considerable interactions among HIV care services, we model the dynamics of combinations of increases in HIV care continuum targets to identify those that would achieve 25% reductions in annual incidence and diagnoses. METHODS: We used Progression and Transmission of HIV/AIDS (PATH 2.0), an agent-based dynamic stochastic simulation of HIV in the United States. RESULTS: A 25% reduction in annual incidence could be achieved by multiple alternative combinations of percentages of persons with diagnosed infection and persons with viral suppression including 85% and 68%, respectively, and 90% and 59%, respectively. The first combination corresponded to an 18% reduction in annual diagnoses, and infections being diagnosed at a median CD4 count of 372 cells/muL or approximately 3.8 years from time of infection. The corresponding values on the second combination are 4%, 462 cells/muL, and 2.0 years, respectively. CONCLUSIONS: Our analysis provides policy makers with specific targets and alternative choices to achieve the goal of a 25% reduction in HIV incidence. Reducing annual diagnoses does not equate to reducing annual incidence. Instead, progress toward reducing incidence can be measured by monitoring HIV surveillance data trends in CD4 count at diagnosis along with the proportion who have achieved viral suppression to determine where to focus local programmatic efforts. |
Progression and Transmission of HIV/AIDS (PATH 2.0).
Gopalappa C , Farnham PG , Chen YH , Sansom SL . Med Decis Making 2016 37 (2) 224-233 BACKGROUND: HIV transmission is the result of complex dynamics in the risk behaviors, partnership choices, disease stage and position along the HIV care continuum-individual characteristics that themselves can change over time. Capturing these dynamics and simulating transmissions to understand the chief sources of transmission remain important for prevention. METHODS: The Progression and Transmission of HIV/AIDS (PATH 2.0) is an agent-based model of a sample of 10,000 people living with HIV (PLWH), who represent all men who have sex with men (MSM) and heterosexuals living with HIV in the U.S.A. Persons uninfected were modeled as populations, stratified by risk and gender. The model included detailed individual-level data from several large national surveillance databases. The outcomes focused on average annual transmission rates from 2008 through 2011 by disease stage, HIV care continuum, and sexual risk group. RESULTS: The relative risk of transmission of those in the acute phase was nine-times [5th and 95th percentile simulation interval (SI): 7, 12] that of those in the non-acute phase, although, on average, those with acute infections comprised 1% of all PLWH. The relative risk of transmission was 24- to 50-times as high for those in the non-acute phase who had not achieved viral load suppression as compared with those who had. The relative risk of transmission among MSM was 3.2-times [SI: 2.7, 4.0] that of heterosexuals. Men who have sex with men and women generated 46% of sexually acquired transmissions among heterosexuals. CONCLUSIONS: The model results support a continued focus on early diagnosis, treatment and adherence to ART, with an emphasis on prevention efforts for MSM, a subgroup of whom appear to play a role in transmission to heterosexuals. |
Facial nerve palsy including Bell's palsy: case definitions and guidelines for collection, analysis, and presentation of immunisation safety data
Rath B , Gidudu JF , Anyoti H , Bollweg B , Caubel P , Chen YH , Cornblath D , Fernandopulle R , Fries L , Galama J , Gibbs N , Grilli G , Grogan P , Hartmann K , Heininger U , Hudson MJ , Izurieta HS , Jevaji I , Johnson WM , Jones J , Keller-Stanislawski B , Klein J , Kohl K , Kokotis P , Li Y , Linder T , Oleske J , Richard G , Shafshak T , Vajdy M , Wong V , Sejvar J . Vaccine 2016 35 (15) 1972-1983 Facial nerve palsy is classified based on the location of its lesion. Central facial nerve palsy is the consequence of an upper motor neuron (UMN) lesion of the 7th cranial nerve, while peripheral palsy is due to a lesion of a lower motor neuron (LMN). Peripheral facial nerve palsy is the partial (i.e., paresis) or complete (i.e., paralysis) loss of function of some or all the structures innervated by the facial nerve (i.e. cranial nerve VII). Facial nerve palsy is also classified by the time course of its development depending on whether acute (minutes to days), subacute (days to weeks) or chronic (longer than weeks). Acute onset facial palsies are common. The most common cause of acute onset, central facial palsy is stroke. However, of the acute onset, peripheral facial palsies, the most common syndrome is that of idiopathic, acute onset, peripheral facial palsy, better known as Bell's palsy. Henceforth in this document, it will be understood that, when discussing Bell's palsy, we are referring to peripheral facial palsy that is ‘acute-onset’. | Clinical signs of peripheral facial nerve palsy include loss of facial tone with obliteration of the naso-labial fold, inability to raise the eyebrows and wrinkle the forehead, smile, open or draw the corner of the mouth, and completely close the eye on the affected side [1], [2], [3], [4]. They may further include hyperacusis, dryness of eye and decreased salivation. Peripheral facial nerve palsy most commonly presents on one side of the face, leading to facial asymmetry, or “facial droop” [1], [5]. Simultaneous bilateral acute-onset cases have also been described and are now recognised as an uncommon clinical feature [6], [7], [8], [9], [10], [11], [12], [13]. |
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