Secondary Transmission Research Articles

Old Enemy with a New Face: Re-emerging Monkeypox Disease – An Update

Human monkeypox (MPX), a multi-country re-emerging disease, is rapidly spreading around the world. The etiological agent of this disease, Monkeypox virus (MPXV), is a DNA virus classified into three genetic types (West Africa, Congo Basin clade, and one new clade-3). Atypical or unusual symptoms as well as asymptomatic infection of MPXV has also been reported. Transmission among humans is possible by droplets, contact, sexual intercourse, and fomites. Secondary transmission of this disease has been reported to occur in less than 10% of cases where it was found 35%–88% of smallpox. Mother-to-fetus transmission by vertical route is also possible for this disease. Modern equipment, biosafety level-3 laboratory facilities, and trained expert persons are needed to diagnose this disease. Previous data support that ~85% clinical protection is provided by smallpox vaccines for monkeypox, although initially non-human primates models were used for various experiments, and also side-effects of this vaccine have been notably mentioned in various studies. Limited research findings of JYNNEOS vaccine has supported the comparatively lower prevalence of MPX cases with vaccination. Few drugs, including cidofovir, tecovirimat, brincidofovir, and vaccinia immune globulin intravenous are preferable against this disease, although clinical trial data is limited and FDA-approval is also pending. This review-based study presents an overall scenario of Monkeypox disease (MPXD) based on previously published studies. Recommended clinical treatment and vaccination, appropriate infection prevention and control strategies, adopting one health approach, and quick identification of hotspots using a wastewater-based surveillance system need to be followed to check the further spread of MPX outbreaks.

Frequency Allocation Based on FFR and SWF Algorithm Fusion of Large Trading Area Under the Condition of COVID-19

The highest level of epidemic prevention and control is precise prevention and control. That is to say, through rapid flow adjustment, we can track down all the close contacts and sub-close contacts, and only isolate them without affecting the work and life of others. Of course, it is difficult to achieve absolute precision prevention and control, so how to measure the degree of precision prevention and control in a region with a quantitative method. How to achieve the balance between security, efficiency, and economy under the abnormal background. From the perspective of safety, the prevention and control of the COVID-19 epidemic are still in a critical period. Once it is not carefully controlled, it may still cause secondary transmission, which will bring huge losses to the city's epidemic prevention work and the safety of residents' lives and property. Therefore, in order to immediately feedback on potential infectious sources, we created the fusion of FFR and SWF algorithms to expand the frequency capacity. The supervisors of large business districts can ensure that the frequency is distributed among as many groups as possible through the greater capacity to improve the information inspection mechanism.

The calcium cyanamide and polyethylene blocks the secondary transmission and infection of vegetable leaf diseases.

Continuous cropping obstacles, especially soil-borne diseases can cause serious harm to agricultural production and limit the sustainable development of modern agriculture. However, Corynespora blight is an important air-borne disease on cucumber leaves caused by Corynespora cassiicola. The pathogen also could survive in air-dried soil or plant residue for at least one month. However, it is not clear whether soil Corynespora blight residues can infect plants. We detected the dynamic change of C. cassiicola content in soil and air after returning the diseased and residual straw to the field in real time by PMA-qPCR detection method. In this study, we reveal for the first time a new mode of transmission in which leaf blade disease residues in soil can spread again into the air and infect plants. In polyethylene (PE) treatment, cucumber plants grew healthily without disease. However, the content of C. cassiicola in the soil still existed in the PE treatment at 103 spore·g-1. The disease index (DI) of cucumber was less than 3 in calcium cyanamide (CaCN2). After fumigation and film removal and the whole growth period was controlled at a safe level. In addition, the PMA-qPCR detection method of Corynespora blight of cucumber was established for the first time in this study. In summary, CaCN2 and PE treatments are effective ways to block the infection of cucumber leaves by Corynespora blight residues in soil. These treatments are considered to comprise a feasible and sustainable technique for vegetable leaf residues in greenhouses.

Viral Breakthrough Episodes Among Persons with HIV in Care in Alberta, Canada: Clinical and Public Health Implications.

Unsuppressed HIV viremia damages immunity and increases the risk for secondary HIV transmission. Successful engagement of persons with HIV (PWH) into care resulting in viral suppression is vital. PWH already engaged in care, who, after achieving viral suppression, experience viral breakthrough episodes (VBEs) with a sequence of suppressed/unsuppressed/suppressed viral loads remain problematic. We examined the frequency and outcomes of PWH experiencing VBE. HIV care is provided at no cost to all patients under Alberta's universal health program. All PWH followed at Southern Alberta Clinic, Canada, with two or more viral load tests between January 1, 2010, and January 1, 2020, were evaluated. Sociodemographic, clinical, and lifestyle variables were determined along with health outcomes (CD4 levels, HIV-related hospitalizations, and HIV/AIDS-related mortality). Descriptive and multi-variable analyses were performed comparing PWH with and without VBEs. Of 2096 PWH, 386 (18%) experienced one or more VBEs. A higher risk of VBEs was seen in adjusted analyses in those diagnosed age ≤40 years. Increased risk of VBE was seen with injection drug use (46%) and in heterosexuals (56%) compared with MSM. Experience of intimate partner violence, unstable housing, homelessness, and past incarceration also increased risks by 36%, 44% 79%, and 51%, respectively. PWH with VBEs experienced lower CD4 counts (median -417/mm3 vs. 576/mm3), higher rates of HIV-related hospitalizations (16% vs. 5%), and a 67% increased risk of death (95% confidence interval 1.17-2.39) over the study period. Nearly 20% of all PWH, after achieving viral suppression, experienced VBEs. Distinct clinical, lifestyle, and life experiences predict PWH at greatest risk for more than one VBEs. Serious negative health outcomes of VBEs were identified, suggesting that novel customized care programming is required for PWH at greatest risk.

382. Are errors of omission falsely inflating hospital-onset Clostridioides difficile infection numbers?

Abstract Background Identification of C. difficile infection (CDI) as community onset (CO) versus hospital onset (HO) is based upon the timing of the laboratory testing. Any lab diagnosis made after day 3 of hospitalization is classified as HO-CDI, even if there is clinical evidence that the patient had CDI before lab testing was sent on day 4 or later. Capturing CDI infection early in hospitalization is essential to proper diagnosis and management of CDI. Methods This is a single center retrospective study of all HO-CDI cases identified from January 2018 through January 2022. All cases were reviewed to determine if patients had loose stools during days 1-3 which were not tested, as these may have been missed opportunities to diagnose CO-CDI. We used nursing flowsheet determine if the patient had soft, loose, watery, liquid or pasty stool bowel movements (BM). Results We identified 302 unique patients diagnosed with HO-CDI during the 4 year study period. 181 (60%) were men. The mean age 57 (range 3-98 years), with increasing case numbers with increasing age groups: age 0-18 (19/6.3%), 19-39 (39/12.9%), 40-59 (73/24.2%), ≥ 60 (171/56.6%). Mean time of HO-CDI diagnosis was 12.4 days (range 4-122 days) with a skew towards early onset HO-CDI diagnosis as 86/302 (28.5%) testing positive on days 4-6. Overall, 119/302 (39.0%) of patients had identified missed opportunities for testing stools during days 1-3 of hospitalization. 38/86 (44.2%) of patients with HO-CDI diagnosed on days 4-6 had missed opportunities for testing. 40/302 (13.2%) patients expired during the index hospitalization. Conclusion Better tracking of patients' symptoms, number and consistency of BMs could improve recognition of patients presenting with CO-CDI. In turn, this would help to institute earlier isolation and treatment of these patients, as well as decreasing HO-CDI resulting from late recognition of CO-CDI which may falsely inflate HO-CDI case numbers, and/or lead to secondary hospital transmission from delayed isolation of patients with CDI. Our findings likely represent a significant under estimation of the magnitude of the errors of omission of missing opportunities for early diagnosis of CDI since it based on review of nursing flowsheets which often miss the number and consistency of patients' BMs. Disclosures Jorge Paiva Parada, MD MPH, Shionogi: Honoraria.

An outbreak of hepatitis A virus infection in a secondary school in England with no undetected asymptomatic transmission among students.

In June 2019 the Health Protection Team in Yorkshire and Humber, England, was notified of cases of hepatitis A virus (HAV) infection in staff at a secondary school. Investigation revealed that an earlier case worked as a food handler in the school kitchen. Indirect transmission through food from the canteen was considered the most likely route of transmission. Cases were described according to setting of exposure. Oral fluid was obtained from students for serological testing. Environmental investigations were undertaken at settings where food handling was considered a potential transmission risk. Thirty-three confirmed cases were linked to the outbreak. All of those tested (n = 31) shared the same sequence with a HAV IB genotype. The first three cases were a household cluster and included the index case for the school. A further 19 cases (16 students, 3 staff) were associated with the school and consistent with indirect exposure to the food handler. One late onset case could not be ruled out as a secondary case within the school and resulted in vaccination of the school population. Five cases were linked to a bakery where a case from the initial household cluster worked as a food server. No concerns about hygiene standards were noted at either the school or the bakery. Oral fluid samples taken at the time of vaccination from asymptomatic students (n = 219, 11-16 years-old) showed no evidence of recent or current infection. This outbreak included household and foodborne transmission but limited (and possibly zero) person-to-person transmission among secondary school students. Where adequate hygiene exists, secondary transmission within older students may not occur.

Experience in emergency response to 2019-nCoV positive cases in an international test competition

Objective: To analyze the performance of emergency response to 2019 novel coronavirus (2019-nCoV) positive cases in an international test competition in an Winter Olympic Game venue and provide evidences for the COVID-19 prevention and control in similar competitions. Methods: A retrospective analysis on the epidemiological investigation and nucleic acid test results of the cases, the implementation of prevention and control measures, including the communication with sport teams and others, was conducted. Results: The positive cases of 2019-nCoV among entering people were detected before entry, at airport, hotel and venue. Two positive cases were reported before entry, 2 positive cases infected previously and 3 asymptomatic cases were reported after the entry. The venue public health team and local CDC conducted epidemiological investigation and contact assessment jointly in a timely and efficient manner. No local secondary transmission occurred, but the nucleic acid test results of positive persons fluctuated, posing serious challenges to the implementation of prevention and control measures. Conclusion: In large scale international competition, there is high risk of imported COVID-19. It is necessary to fully consider the fluctuation of nucleic acid test results, the criteria for determination and cancellation of positive results and give warm care to positive cases in the emergency response.

Risk of transmission of COVID-19 from healthcare workers returning to work after a 5-day isolation, and kinetics of shedding of viable SARS-CoV-2 variant B.1.1.529 (Omicron)

There have been limited data on the risk of onward transmission from individuals with Omicron variant infections who return to work after a 5-day isolation. We evaluated the risk of transmission from healthcare workers (HCWs) with Omicron variant who returned to work after a 5-day isolation and the viable virus shedding kinetics. This investigation was performed in a tertiary care hospital, Seoul, South Korea. In a secondary transmission study, we retrospectively reviewed the data of HCWs confirmed as COVID-19 from March 14 to April 3, 2022 in units with 5 or more COVID-19-infected HCWs per week. In the viral shedding kinetics study, HCWs with Omicron variant infection who agreed with daily saliva sampling were enrolled between February and March, 2022. Of the 248 HCWs who were diagnosed with COVID-19 within 5 days of the return of an infected HCW, 18 (7%) had contact with the returned HCW within 1 to 5 days after their return. Of these, 9 (4%) had an epidemiologic link other than with the returning HCW, and 9 (4%) had contact with the returning HCW, without any other epidemiologic link. In the study of the kinetics of virus shedding (n=32), the median time from symptom onset to negative conversion of viable virus was 4 days (95% CI, 3 to 5 days). Our data suggest that the residual risk of virus transmission after 5 days of isolation following diagnosis or symptom onset is low.

Prevalence of Late Presenters and Advanced HIV Disease in HIV Patients and Their Related Factors in Iran: Results from 19 Years of National Surveillance HIV Data.

Late presenters (LP) and Advanced HIV Disease (AHD) represent important missed opportunities to reduce secondary transmission and undesirable HIV outcomes. Despite efforts, the diagnoses are still delayed for the majority of patients. This cross-sectional study was conducted using the Iranian national HIV surveillance database from 2001 to 2019, to determine the factors affecting AHD and LP in Iran. To determine LP (CD4 ≤ 350 cells/μL) and AHD (CD4 ≤ 200 cells/μL), the first patients' CD4 at baseline were used. To examine the relationship between the covariates and LP or AHD, a Logistic Regression was applied. The adjusted odds ratio (AOR) stated to report the relationship. Totally, 13,571 patients were included in the study. Of these, 4,060 (29.92%) were AHD and 7,161 (52.77%) LP. Female gender [AOR = 0.88, 95% confidence interval (CI): 0.80-0.97], higher education (AOR = 0.80, 95% CI: 0.69-0.93), and having a positive HIV spouse (AOR = 0.75, 95% CI = 0.66-0.85) significantly decreased odds of LP (p < .05). However, older age (AOR = 2.53, 95% CI: 2.20-2.91) was a risk factor for LP. For AHD, years of detection (AOR = 1.16, 95% CI: 1.06-1.27), older age (AOR = 2.49, 95% CI: 2.12-2.92), and having a spouse with high-risk behavior (AOR = 1.23, 95% CI: 1.02-1.49) led to higher odds. (p < .05). Also, female (AOR = 0.82, 95% CI: 0.73-0.92) and having a positive HIV spouse (AOR = 0.67, 95% CI: 0.58-0.78) were protective factors for ADH. The present study estimated that approximately two-thirds of HIV patients are LP and one-third are AHD in Iran. Older age, male gender, lower education, and having a spouse with high-risk behavior were the factors affecting LP and AHD. Thus, to reduce the percentage of patients with LP and AHD in Iran, improvements in knowledge and periodic screening programs are necessary for these groups.

Decrease in overdispersed secondary transmission of COVID-19 over time in Japan.

Coronavirus disease 2019 (COVID-19) has been described as having an overdispersed offspring distribution, i.e. high variation in the number of secondary transmissions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) per single primary COVID-19 case. Accordingly, countermeasures focused on high-risk settings and contact tracing could efficiently reduce secondary transmissions. However, as variants of concern with elevated transmissibility continue to emerge, controlling COVID-19 with such focused approaches has become difficult. It is vital to quantify temporal variations in the offspring distribution dispersibility. Here, we investigated offspring distributions for periods when the ancestral variant was still dominant (summer, 2020; wave 2) and when Alpha variant (B.1.1.7) was prevailing (spring, 2021; wave 4). The dispersion parameter (k) was estimated by analysing contact tracing data and fitting a negative binomial distribution to empirically observed offspring distributions from Nagano, Japan. The offspring distribution was less dispersed in wave 4 (k = 0.32; 95% confidence interval (CI) 0.24-0.43) than in wave 2 (k = 0.21 (95% CI 0.13-0.36)). A high proportion of household transmission was observed in wave 4, although the proportion of secondary transmissions generating more than five secondary cases did not vary over time. With this decreased variation, the effectiveness of risk group-focused interventions may be diminished.

Lassa fever. Part 2. Laboratory diagnostics, treatment, development of medications

Globalization and high-speed means of transportation contribute to the spread of infections dangerous to humans. Airborne pathogens have pandemic potential as currently shown in case of the novel coronavirus SARS-CoV-2. Natural focal Lassa fever (LF) common in West African countries, in 35 cases was registered in non-endemic geographical areas because any person infected with Lassa virus (LASV) is a long-term source of infection (up to two months). Cases of person-to-person infection in endemic territories are described. In Germany, the facts of secondary virus transmission from patients to doctors have been recorded during the examination and blood collection from an apparently healthy person as well as during the autopsy of a deceased subjects due to severe LF course. Nonspecific malaise symptoms in LF are also characteristic of numerous other diseases common on the African continent, e.g., malaria and typhoid fever or viral infections such as yellow fever, Chikungunya, dengue and Zika, monkey pox and Ebola virus disease. In this regard, there may be similar dermatological manifestations. Timely detection of cases and differential diagnosis are crucial to ensure safe patient care and use of affordable antiviral therapy for LL provided by the drug Ribavirin. Research methods for studying LASV use polymerase chain reaction (PCR) for detecting viral RNA, electron microscopy, isolation of infectious virus cultured sensitive cells, indirect immunofluorescence reaction, enzyme immunoassay (ELISA) and immunochromatographic assays for the detection of antibodies and/or antigen as well as immunoblotting. Currently, test kits based on molecular and genetic methods are mainly used for LF laboratory diagnostics. Since the 1980s, ribavirin has been used to treat patients with LF. The serum accumulation of the drug in large quantities causes hemolysis, development of anemia and impaired renal function. In this regard, treatment options are being considered with decline in its concentration due to combined use with other antiviral drugs. A search for new therapeutic agents capable of inhibiting viral replication at disease early stage has been in progress due to lack of any approved vaccines.

Correlation between times to SARS-CoV-2 symptom onset and secondary transmission undermines epidemic control efforts

Severe acute respiratory coronavirus 2 (SARS-CoV-2) infections have been associated with substantial presymptomatic transmission, which occurs when the generation interval—the time between infection of an individual with a pathogen and transmission of the pathogen to another individual—is shorter than the incubation period—the time between infection and symptom onset. We collected a dataset of 257 SARS-CoV-2 transmission pairs in Japan during 2020 and jointly estimated the mean incubation period of infectors (4.8 days, 95 % CrI: 4.4–5.1 days), mean generation interval to when they infect others (4.3 days, 95 % credible interval [CrI]: 4.0–4.7 days), and the correlation (Kendall’s tau: 0.5, 95 % CrI: 0.4–0.6) between these two epidemiological parameters. Our finding of a positive correlation and mean generation interval shorter than the mean infector incubation period indicates ample infectiousness before symptom onset and suggests that reliance on isolation of symptomatic COVID-19 cases as a focal point of control efforts is insufficient to address the challenges posed by SARS-CoV-2 transmission dynamics.

Molecular identification of vivax malaria relapse patients in the Yunnan Province based on homology analysis of the Plasmodium vivax circumsporozoite protein gene

More than 85% of the malaria burden in the Yunnan Province is caused by imported vivax malaria, and Yunnan is also where the majority of vivax malaria patients are diagnosed in China. Timely removal of the infection sources of Plasmodium vivax and its breeding environment remains the key to eliminating the secondary transmission of imported malaria. To that end, blood samples were collected from cases diagnosed and revalidated as single species infection with P. vivax in the Yunnan Province from 2013 to 2020. Specifically, samples from vivax malaria patients with suspected relapses episodes were subjected to PCR amplification, product sequencing, and analysis of the P. vivax circumsporozoite protein (pvcsp) gene. In total, 77 suspected relapse patients were identified out of 2484 cases infected with P. vivax, with a total of 81 recurrent episodes. A total of 156 CDS (coding DNA sequence) chains were obtained through PCR amplification and sequencing of the pvcsp gene from 159 blood samples, 121 of which can be matched to the paired sequences of 59 vivax malaria patients with both primary attack and recurrent experience. Of the 59 pairs of pvcsp gene sequences, every one of 31 pairs showed only one haplotype and no variant sites (VS), meaning every two paired sequence was completely homologous. Every one of the remaining 28 paired sequences had two haplotypes but no length polymorphism, indicating that the paired sequences was “weakly heterologous” with no fragment insertions (or deletions). All 59 vivax malaria patients with recurrences were caused by the activation of P. vivax hypnozoites originated from the same population as the primary infection. The paired analysis of the similarity between high variant genes allowed the identification of relapse episodes caused by P. vivax homologous hypnozoites and also demonstrated pvcsp gene as one of the candidate molecular markers for tracing infection origin.

Animal Models Used in Monkeypox Research.

Monkeypox is an emerging zoonotic disease with a growing prevalence outside of its endemic area, posing a significant threat to public health. Despite the epidemiological and field investigations of monkeypox, little is known about its maintenance in natural reservoirs, biological implications or disease management. African rodents are considered possible reservoirs, although many mammalian species have been naturally infected with the monkeypox virus (MPXV). The involvement of domestic livestock and pets in spillover events cannot be ruled out, which may facilitate secondary virus transmission to humans. Investigation of MPXV infection in putative reservoir species and non-human primates experimentally uncovered novel findings relevant to the course of pathogenesis, virulence factors and transmission of MPXV that provided valuable information for designing appropriate prevention measures and effective vaccines.

Dealing with Hidden Threats: The Antimicrobial Effect of the Embalming Process.

Individuals naturally carry bacteria and other microbes as part of their natural flora, with some being opportunistic pathogens. Approximately 30% of the population is known to carry Staphylococcus aureus in their nasal cavity, an organism that causes infections ranging from soft tissue abscesses to toxic shock syndrome. This problem is compounded by the presence of antibiotic-resistant strains such as Methicillin-Resistant Staphylococcus aureus (MRSA). Commensal bacteria present on cadavers pose a risk to those who handle the body. As a Medical School Anatomy laboratory that performs hands-on cadaveric dissection, we wanted to know whether the embalming process is sufficient to kill all commensal bacteria that pose a risk to staff and students. Even if these strains do not cause disease in these individuals, secondary transmission could occur to friends and family, who may be at higher risk of acquiring an infection. Embalming is assumed to eliminate all microbial contamination on the body. However, there are limited studies to confirm this. This study characterises the incidence of antibiotic sensitive and resistant bacteria in cadavers donated for medical teaching and research. We have screened for Methicillin-Resistant Organisms (MRO) and Extended-Spectrum Beta-Lactamase (ESBL) producing bacteria. In this study group of cadavers, approximately 46% (16/35) carry an MRO, while 51% (18/35) carry an ESBL positive organism prior to embalming. By determining the organisms' presence pre- and post-embalming, we can evaluate the embalming procedure's effectiveness. Our results show embalming eliminates detectable microbes in about 51% (18/35) of the cadavers. MRO dropped by 75% (16 to 4 positive cadavers), while ESBL organisms went down by almost 95% (from 18 to 1 positive cadaver). There was a further decrease in the number of positive cadavers after storage at 4 °C to 6% (2/32). Thus, although the embalming process does not immediately sterilise all the cadavers, prolonged storage at 4 °C can further reduce the number of viable bacteria.

One health genomic surveillance and response to a university-based outbreak of the SARS-CoV-2 Delta AY.25 lineage, Arizona, 2021.

Genomic surveillance and wastewater tracking strategies were used to strengthen the public health response to an outbreak of the SARS-CoV-2 Delta AY.25 lineage associated with a university campus in Arizona. Epidemiologic and clinical data routinely gathered through contact tracing were matched to SARS-CoV-2 genomes belonging to an outbreak of AY.25 identified through ongoing phylogenomic analyses. Continued phylogenetic analyses were conducted to further describe the AY.25 outbreak. Wastewater collected twice weekly from sites across campus was tested for SARS-CoV-2 by RT-qPCR, and subsequently sequenced to identify variants. The AY.25 outbreak was defined by a single mutation (C18804T) and comprised 379 genomes from SARS-CoV-2 positive cases associated with the university and community. Several undergraduate student gatherings and congregate living settings on campus likely contributed to the rapid spread of COVID-19 across the university with secondary transmission into the community. The clade defining mutation was also found in wastewater samples collected from around student dormitories a week before the semester began, and 9 days before cases were identified. Genomic, epidemiologic, and wastewater surveillance provided evidence that an AY.25 clone was likely imported into the university setting just prior to the onset of the Fall 2021 semester, rapidly spread through a subset of the student population, and then subsequent spillover occurred in the surrounding community. The university and local public health department worked closely together to facilitate timely reporting of cases, identification of close contacts, and other necessary response and mitigation strategies. The emergence of new SARS-CoV-2 variants and potential threat of other infectious disease outbreaks on university campuses presents an opportunity for future comprehensive One Health genomic data driven, targeted interventions.

A matching game framework for users clustering and resource allocation with wireless power transfer in a CR‐NOMA network

SummaryThis paper investigates the resource allocation in a massively deployed user cognitive radio enabled non‐orthogonal multiple access (CR‐NOMA) network considering the downlink scenario. The system performance deteriorates with the number of users who are experiencing similar channel characteristics from the base station (BS) in NOMA. To address this challenge, we propose a framework for maximizing the system throughput that is based on one‐to‐one matching game theory integrated with the machine learning technique. The proposed approach is decomposed to solve users clustering and power allocation subproblems. The selection of optimal cluster heads (CHs) and their associated cluster members is based on Gale‐Shapley matching game theoretical model with the application of Hungarian method. The CHs can harvest energy from the BS and transfer their surplus power to the primary user (PU) through wireless power transfer. In return, they are allowed to access the licensed band for secondary transmission. The power allocation to the users intended for power conservation at CHs is formulated as a probabilistic constraint, which is then solved by employing the support vector machine (SVM) algorithm. The simulation results demonstrate the efficacy of our proposed schemes that enable the CHs to transfer the residual power while ensuring maximum system throughput. The effects of different parameters on the performance are also studied.

The Potential Role of an Adjunctive Real-Time Locating System in Preventing Secondary Transmission of SARS-CoV-2 in a Hospital Environment: Retrospective Case-Control Study

BackgroundThere has been an increasing demand for new technologies regarding infection control in hospital settings to reduce the burden of contact tracing.ObjectiveThis study aimed to compare the validity of a real-time locating system (RTLS) with that of the conventional contact tracing method for identifying high-risk contact cases associated with the secondary transmission of SARS-CoV-2.MethodsA retrospective case-control study involving in-hospital contact cases of confirmed COVID-19 patients, who were diagnosed from January 23 to March 25, 2022, was conducted at a university hospital in South Korea. Contact cases were identified using either the conventional method or the RTLS. The primary endpoint of this study was secondary transmission of SARS-CoV-2 among contact cases. Univariate and multivariable logistic regression analysis comparing test positive and versus negative contact cases were performed.ResultsOverall, 509 and 653 cases were confirmed by the conventional method and the RTLS, respectively. Only 74 contact cases were identified by both methods, which could be attributed to the limitations of each method. Sensitivity was higher for the RTLS tracing method (653/1088, 60.0%) than the conventional tracing method (509/1088, 46.8%) considering all contact cases identified by both methods. The secondary transmission rate in the RTLS model was 8.1%, while that in the conventional model was 5.3%. The multivariable logistic regression model revealed that the RTLS was more capable of detecting secondary transmission than the conventional method (adjusted odds ratio 6.15, 95% CI 1.92-28.69; P=.007).ConclusionsThis study showed that the RTLS is beneficial when used as an adjunctive approach to the conventional method for contact tracing associated with secondary transmission. However, the RTLS cannot completely replace traditional contact tracing.

The role of depression in secondary HIV transmission among people who inject drugs in Vietnam: A mathematical modeling analysis.

Among people who inject drugs (PWID), depression burden is high and may interfere with HIV prevention efforts. Although depression is known to affect injecting behaviors and HIV treatment, its overall impact on HIV transmission has not been quantified. Using mathematical modeling, we sought to estimate secondary HIV transmissions and identify differences by depression among PWID. We analyzed longitudinal data from 455 PWID living with HIV in Vietnam during 2009-2013. Using a Bernoulli process model with individual-level viral load and behavioral data from baseline and 6-month follow-up visits, we estimated secondary HIV transmission events from participants to their potentially susceptible injecting partners. To evaluate differences by depression, we compared modeled transmissions per 1,000 PWID across depressive symptom categories (severe, mild, or no symptoms) in the three months before each visit. We estimated a median of 41.2 (2.5th, 97.5th percentiles: 33.2-49.2) secondary transmissions from all reported acts of sharing injection equipment with 833 injecting partners in the three months before baseline. Nearly half (41%) of modeled transmissions arose from fewer than 5% of participants in that period. Modeled transmissions per 1,000 PWID in that period were highest for severe depressive symptoms (100.4, 80.6-120.2) vs. mild (87.0, 68.2-109.4) or no symptoms (78.9, 63.4-94.1). Transmission estimates fell to near-zero at the 6-month visit. Secondary transmissions were predicted to increase with depression severity, although most arose from a small number of participants. Our findings suggest that effective depression interventions could have the important added benefit of reducing HIV transmission among PWID.

A scabies outbreak in an inpatient rehabilitation setting

BackgroundScabies is a skin infection transmitted by close person-to-person contact. Crusted scabies is a more severe type which is more contagious. Delayed diagnosis of scabies could lead to an outbreak. MethodsThe outbreak occurred at a 435-bed academic medical center with 76 inpatient rehabilitation beds. The index patient was incarcerated and admitted to our hospital in February 2022. The patient developed crusted scabies after steroids treatment. ResultsThe patient was treated with oral ivermectin (200 mcg/kg, maximum dose 15 mg) and topical permethrin 5%. All units were followed for 6 weeks since diagnosis of the index patient. A total of 46 healthcare workers (20 nurses and 26 physical therapists) were exposed. Twenty-nine presented symptoms and were treated with ivermectin and permethrin or only ivermectin. No physicians, other patients, or prison guards were affected. There was no secondary household transmission of those exposed healthcare workers. ConclusionsScabies is highly contagious in high-risk patients. Early diagnosis and effective infection control are of vital importance.