Differences In Transmission Rates Research Articles

Comparing the transmission of carbapenemase-producing and extended-spectrum beta-lactamase-producing Escherichia coli between broiler chickens.

The emergence of carbapenemase-producing Enterobacteriaceae (CPE) is a threat to public health, because of their resistance to clinically important carbapenem antibiotics. The emergence of CPE in meat-producing animals is particularly worrying because consumption of meat contaminated with resistant bacteria comparable to CPE, such as extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, contributed to colonization in humans worldwide. Currently, no data on the transmission of CPE in livestock is available. We performed a transmission experiment to quantify the transmission of CPE between broilers to fill this knowledge gap and to compare the transmission rates of CPE and other antibiotic-resistant E. coli. A total of 180 Ross 308 broiler chickens were distributed over 12 pens on the day of hatch (day 0). On day 5, half of the 10 remaining chickens in each pen were orally inoculated with 5·102 colony-forming units of CPE, ESBL, or chloramphenicol-resistant E. coli (catA1). To evaluate the effect of antibiotic treatment, amoxicillin was given twice daily in drinking water in 6 of the 12 pens from days 2-6. Cloacal swabs of all animals were taken to determine the number of infectious broilers. We used a Bayesian hierarchical model to quantify the transmission of the E. coli strains. E. coli can survive in the environment and serve as a reservoir. Therefore, the susceptible-infectious transmission model was adapted to account for the transmission of resistant bacteria from the environment. In addition, the caecal microbiome was analyzed on day 5 and at the end of the experiment on day 14 to assess the relationship between the caecal microbiome and the transmission rates. The transmission rates of CPE were 52 - 68 per cent lower compared to ESBL and catA1, but it is not clear if these differences were caused by differences between the resistance genes or by other differences between the E. coli strains. Differences between the groups in transmission rates and microbiome diversity did not correspond to each other, indicating that differences in transmission rates were probably not caused by major differences in the community structure in the caecal microbiome. Amoxicillin treatment from day 2-6 increased the transmission rate more than three-fold in all inoculums. It also increased alpha-diversity compared to untreated animals on day 5, but not on day 14, suggesting only a temporary effect. Future research could incorporate more complex transmission models with different species of resistant bacteria into the Bayesian hierarchical model.

Heterogeneous exchange rate pass-through in Mexico: What drives it?

In this paper, we focus on the pass-through of exchange rate fluctuations into prices of final goods and services and examine whether contrasting pass-through rates are associated with regional and/or product-specific characteristics. Using CPI micro-data from 2002 to 2010, we estimate industry-specific rates of pass-through across regions in Mexico. By looking at within-country price responses, we alleviate shortcomings of cross-country studies that assess pass-through determinants. The results indicate that pass-through rates differ across regions and industries: low pass-through regions exhibit nearly one-quarter of the elasticity shown by high pass-through regions after twelve months. This heterogeneity prevails at longer horizons. The findings suggest that full pass-through is rejected for all regions and industries. Most of these differences in transmission rates are explained by regional and product characteristics: demand conditions, economic development, distance to the US border, import intensity, price change dispersion and expenditure share play a clear role in increasing pass-through, whereas market density dampens pass-through rates. The evidence confirms pricing-to-market theories and has implications for the design of monetary and exchange rate policies.

How COVID-19 spread varied by resident length of stay and resident–staff transmission pathways over time in US nursing homes

Background: Pathogen transmission among staff and residents in nursing homes can vary depending on their interactions and by the amount of time a resident receives care in the facility. Understanding the relative differences in transmission rates between and among staff and residents can identify the pathways that contributed most to the spread of SARS-CoV-2 in US nursing homes. Further exploring relative differences by categorizing facilities by residents’ lengths of stay can identify priority categories for intervention. Methods: Using US National Healthcare Safety Network (NHSN) surveillance data on resident and staff cases, vaccination, and resident deaths during June 2020–June 2022, we estimated SARS-CoV-2 transmission among and between residents and staff. We used a Bayesian inversion of a susceptible–exposed–infected–removed–virus–death (SEIRVD) compartmental model to produce the estimates. The facilities were divided into those with median length of stay (LOS) among the residents of 10 weeks. Additional inputs included the incidence and vaccination levels of the county where each facility was located. For the compartmental model, all data were averaged to form a representative facility for each category. Transmission was estimated separately for 3 periods: (1) June 2020–March 2021 as before the SARS-CoV-2 delta variant, (2) April 2021—October 2021 during SARS-CoV-2 delta variant dominance, and (3) November 2021—June 2022 during the prevalence of the SARS-CoV-2 omicron variant. Results: Regardless of facility category, transmission was highest from staff to residents or resident to resident (Fig.). These estimates of transmission were highest during the pre–SARS-CoV-2 delta variant phase. Transmission in that phase was highest in the facilities with LOS >10 weeks from staff to residents at 0.88 per week (95% credible interval [CrI], 0.06–1.85), in the facilities with LOS 6–10 weeks from staff to residents at 0.68 per week (95% CrI, 0.03–1.78), and in the facilities with LOS <6 weeks between residents at 0.47 per week (95% CrI, 0.02–0.95). Conclusions: Staff-to-resident or resident-to-resident transmission were the dominant pathways of spread of SARS-CoV-2 across the periods or the facility categories. Facilities with LOS 6 weeks or longer had higher median transmission estimates across the periods and transmission routes compared to facilities with LOS less than 6 weeks, implying that when prioritization of intervention resources is needed, facilities caring for populations with longer stays could be prioritized.Disclosures: None

Back-to-Africa introductions of Mycobacterium tuberculosis as the main cause of tuberculosis in Dar es Salaam, Tanzania.

In settings with high tuberculosis (TB) endemicity, distinct genotypes of the Mycobacterium tuberculosis complex (MTBC) often differ in prevalence. However, the factors leading to these differences remain poorly understood. Here we studied the MTBC population in Dar es Salaam, Tanzania over a six-year period, using 1,082 unique patient-derived MTBC whole-genome sequences (WGS) and associated clinical data. We show that the TB epidemic in Dar es Salaam is dominated by multiple MTBC genotypes introduced to Tanzania from different parts of the world during the last 300 years. The most common MTBC genotypes deriving from these introductions exhibited differences in transmission rates and in the duration of the infectious period, but little differences in overall fitness, as measured by the effective reproductive number. Moreover, measures of disease severity and bacterial load indicated no differences in virulence between these genotypes during active TB. Instead, the combination of an early introduction and a high transmission rate accounted for the high prevalence of L3.1.1, the most dominant MTBC genotype in this setting. Yet, a longer co-existence with the host population did not always result in a higher transmission rate, suggesting that distinct life-history traits have evolved in the different MTBC genotypes. Taken together, our results point to bacterial factors as important determinants of the TB epidemic in Dar es Salaam.

All-optical nano logical gates AND, NOR, OR, and NOT based on plasmonic waveguides with Kerr nonlinear cavity

In this paper, all-optical logical gates were designed and simulated based on Kerr nonlinear circular resonators in order to increase the computational power of an optical central processing unit (CPU) using the two-dimensional finite-difference time-domain (FDTD) method. All the logical gates were designed with a simple and single plasmonic composition in which the switch between the gates is done only by changing the intensity and location of the pumps, signal, and monitor. And this is the novelty of this study, which has been optimized by changing the offset and pulse length of the springs to achieve the maximum transmittance between the OFF and ON states. In addition to the above, a manufacturing tolerance simulation was performed for each gate, which takes into account the probability of error in the experimental production process. Overall, the results showed that the difference in transmission rate for AND, NOR, OR, and NOT was 42%, 95%, 55%, and 92% respectively with an ultrafast time response of up to about 50 fs. The benefits of the present study’s design include the number of gates, high transmission rate, manufacturing tolerance, and a smaller device footprint dimension, all of which make it a good base for the future of photonic computational circuits.

Differential microRNAs expression during ex vivo infection of canine and ovine placental explants with Trypanosoma cruzi and Toxoplasma gondii

Trypanosoma cruzi and Toxoplasma gondii are two zoonotic parasites that constitute significant human and animal health threats, causing a significant economic burden worldwide. Both parasites can be transmitted congenitally, but transmission rates for T. gondii are high, contrary to what has been observed for T. cruzi. The probability of congenital transmission depends on complex interactions between the pathogen and the host, including the modulation of host cell gene expression by miRNAs. During ex vivo infection of canine and ovine placental explants, we evaluated the expression of 3 miRNAs (miR-30e-3p, miR-3074-5p, and miR-127-3p) previously associated with parasitic and placental diseases and modulated by both parasites. In addition, we identified the possible target genes of the miRNAs by using computational prediction tools and performed GO and KEGG enrichment analyses to identify the biological functions and associated pathologies. The three miRNAs are differentially expressed in the canine and ovine placenta in response to T. cruzi and T. gondii. We conclude that the observed differential expression and associated functions might explain, at least partially, the differences in transmission rates and susceptibility to parasite infection in different species.

The Influence of Foureye Butterflyfish (Chaetodon capistratus) and Symbiodiniaceae on the Transmission of Stony Coral Tissue Loss Disease

Marine diseases have caused large scale decreases in coral cover across the Caribbean and are unfortunately projected to increase as sea surface temperatures rise. Identifying the main drivers of disease transmission is essential for our understanding and response to diseases in the future. This study investigates the effects of direct-contact, waterborne, Symbiodiniaceae composition, and butterflyfish foraging on the transmission rates of stony coral tissue loss disease (SCTLD) across Montastraea cavernosa (MCAV) coral fragments. M. cavernosa fragments were placed in direct contact with diseased Orbicella and Montastraea colonies with the purpose of creating disease MCAV fragments for experimental trials with butterflyfish. Three treatments were used to investigate waterborne transmission (control), mechanically injury to a healthy coral (limited), and direct contact feeding across a diseased and healthy coral (unlimited). After the experimental trials, the composition of Symbiodiniaceae was analyzed for every MCAV fragment. Direct contact transmission took on average 3.9 days in 2019 and 11.9 days in 2020 with significantly quicker rates of transmission between donor diseased Orbicella and Montastraea than Montastraea to Montastraea. The composition of Symbiodiniaceae differed significantly between the fragments used in 2019 (dominated by Durusdinium) than in 2020 (dominated by Cladocopium spp.). The limited treatment had the quickest time to transmission compared to the unlimited and control treatments. Symbiodiniaceae differences between 2019 and 2020 might explain differences in transmission rates and overall susceptibility between the years. The species of Symbiodiniaceae may play a role in the susceptibility of corals to the transmission of SCTLD. Additionally, we also have some suggestive evidence that butterflyfish do not directly increase infection rates, but instead might be increasing infection recovery.

Household Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Alpha Variant-United States, 2021.

BackgroundIn Spring 2021, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.7 (Alpha) became the predominant variant in the United States. Research suggests that Alpha has increased transmissibility compared with non-Alpha lineages. We estimated household secondary infection risk (SIR), assessed characteristics associated with transmission, and compared symptoms of persons with Alpha and non-Alpha infections.MethodsWe followed households with SARS-CoV-2 infection for 2 weeks in San Diego County and metropolitan Denver, January to April 2021. We collected epidemiologic information and biospecimens for serology, reverse transcription–polymerase chain reaction (RT-PCR), and whole-genome sequencing. We stratified SIR and symptoms by lineage and identified characteristics associated with transmission using generalized estimating equations.ResultsWe investigated 127 households with 322 household contacts; 72 households (56.7%) had member(s) with secondary infections. SIRs were not significantly higher for Alpha (61.0% [95% confidence interval, 52.4–69.0%]) than non-Alpha (55.6% [44.7–65.9%], P = .49). In households with Alpha, persons who identified as Asian or Hispanic/Latino had significantly higher SIRs than those who identified as White (P = .01 and .03, respectively). Close contact (eg, kissing, hugging) with primary cases was associated with increased transmission for all lineages. Persons with Alpha infection were more likely to report constitutional symptoms than persons with non-Alpha (86.9% vs 76.8%, P = .05).ConclusionsHousehold SIRs were similar for Alpha and non-Alpha. Comparable SIRs may be due to saturation of transmission risk in households due to extensive close contact, or true lack of difference in transmission rates. Avoiding close contact within households may reduce SARS-CoV-2 transmission for all lineages among household members.

Stepped‐Wedge Randomized Clinical Trial of Social Marketing Strategies to Improve Adherence to Remote Monitoring Among Veterans with Pacemakers and Implantable Cardioverter‐Defibrillators

Research ObjectiveRemote monitoring of pacemakers and implantable cardioverter‐defibrillators (ICDs) is a Class 1, Level of Evidence A professional society recommendation and considered standard‐of‐care because it is associated with reduced hospitalizations, death, and need for in‐person pacemaker and ICD checks. However, only 2/3 of patients are adherent to remote monitoring; non‐adherent patients do not receive any benefits of remote monitoring. We sought to compare the effect of two social marketing implementation strategies (protect/warn vs encourage/reward) on improving adherence to remote monitoring among Veterans with pacemakers and ICDs who were non‐adherent to remote monitoring.Study DesignFirst, we designed two informational postcards: 1) a protect/warn postcard describing risks of non‐adherence to remote monitoring (such as delayed notification of heart problems and increased risk of death) and 2) an encourage/reward postcard that framed the same content with a positive/beneficial message. Both postcards contained patient instructions on how to send remote monitoring transmissions. We then conducted a stepped‐wedge randomized controlled trial (RCT). In the first wave, patients were randomized to be mailed a postcard with either one of two messages (protect/warn vs encourage/reward) or no postcard. In the second wave, all patients were mailed a postcard with one of the two messages. In both waves, patients who did not transmit within 1 month were mailed a second postcard with the identical message approximately 1 month later. The primary outcome was the proportion of Veterans who sent a remote monitoring transmission at 10 weeks.Population StudiedWe included Veterans with pacemakers and ICDs who had sent at least one remote monitoring transmission within the past 2 years, but who had missed their last transmission by at least 10 days.Principal FindingsThere were 6331 patients randomized to be mailed a postcard (3166 to a protect/warn message and 3165 to an encourage/reward message) and 2400 controls who were not mailed a postcard (first wave only). The mean age was 73.3 years (standard deviation, 10.3), 98% were men, 76% were White, and 17% were Black or African‐American. Roughly one‐third (37%) had a pacemaker and two‐thirds (62%) had an ICD. A total of 324 postcards (5.1%) were returned as undeliverable. Overall, 2974 patients (49.5%) who received a postcard sent a remote monitoring transmission at 70 days, compared to 565 patients (23.5%) who did not receive a postcard (absolute difference 26.0%, p < 0.001). There was no significant difference in transmission rates between patients randomized to the protect/warn versus the encourage/ reward message (p = 0.51). Twenty‐six percent of patients who sent a transmission did so only after the second postcard was mailed.ConclusionsThis stepped‐wedge RCT found that informational postcards can significantly improve adherence to remote monitoring among patients with pacemakers and ICDs. There was no difference between a protect/warn and encourage/reward social marketing implementation strategy.Implications for Policy or PracticeMailing informational postcards to patients with pacemakers or ICDs who are non‐adherent with remote monitoring can improve adherence. This intervention could improve patient outcomes and reduce the need for avoidable in‐person visits, which is particularly important during the COVID‐19 pandemic.Primary Funding SourceDepartment of Veterans Affairs.

Effects of Interspecific Interactions on Infracommunities of Helminths Parasitizing Creek Chub (Semotilus atromaculatus)

Natural infections of Allocreadium lobatum Wallin, 1909 (Trematoda), Proteocephalus sp. (Cestoda), Rhabdochona canadensis Moravec and Arai, 1971 (Nematoda), Paulisentis missouriensis Keppner, 1974 (Acanthocephala), and Schyzocotyle acheilognathi (Yamaguti, 1934) (Cestoda) in the intestine of creek chub (Semotilus atromaculatus) were analyzed to determine whether patterns of interspecific competition were evident. Data from nearly 2 decades of sampling from the same system were analyzed for patterns of co-occurrence and abundance consistent with negative interactions. Co-occurrence analyses (null models and logistic regression) did not detect negative associations among parasite species. Positive associations among species were more common in null model comparisons. Correlation analyses demonstrated some significant negative correlations between the abundances of pairs of parasite species in some samples, but the overwhelming majority of correlations were insignificant or positive. Previous work did not detect negative microhabitat interactions among the most common helminths studied herein, and together, these results suggest the parasite communities of creek chub in the study area are absent any substantial effect of antagonistic or other negative interspecific interactions. Differences in transmission rate, mode, and spatiotemporal variation are likely dominant processes explaining the patterns observed in the present investigation.

COVID-19 Mathematical Epidemic Model for Impact Analysis of Large Scale Social Restriction: The Case Study of Indonesia

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by Severe Acute Respiratory Syndrome Coronavirus 2. There have been 218,382 confirmed cases of COVID-19, including 8,723 deaths in Indonesia till September 15, 2020. To fight Covid-19, the Indonesian Government modified the lockdown policy to become a large-scale social restriction (LSSR) according to the pandemic level in each region. The LSSR was implemented in DKI Jakarta on April 10, 2020, the epicenter of the Covid-19 outbreak in Indonesia. In this article, we propose the Susceptible-Infected-Hospitalized-Recovered (SIHR) epidemic model for impact analysis of LSSR on epidemic conditions and predict the long-term dynamic COVID-19 in Indonesia. This study extends the SIR model by adding a hospitalized compartment. Finally, we analyze the results of our mathematical model, estimate the model of essential parameters, and predict the disease by considering the real Indonesian cases from March 2 to September 6, 2020. Based on the result, LSSR has a good enough impact on solving the pandemic in Indonesia. One of the factors is because there is a significant difference in transmission rate (β) values. The new normal transmission rate is 75% higher than the LSSR’s.

Seasonal Abundance and Infectivity of Philaenus spumarius (Hemiptera: Aphrophoridae), a Vector of Xylella fastidiosa in California Vineyards.

The meadow spittlebug, Philaenus spumarius (Linnaeus) (Hemiptera: Aphrophoridae), is a vector of the plant pathogen Xylella fastidiosa; however, its role in recent outbreaks of Pierce's disease of grapevine (PD) in California is unclear. While the phenology and ecology of P. spumarius can help determine its contributions to PD epidemics, both remain poorly described in the North Coast vineyards of California. We assessed the phenology of P. spumarius in the region. Spittlemasses were first observed in February or March, while the emergence of adult spittlebugs did not occur until April or May depending on the year. Analysis of sweep and trap data from 2016 to 2018 revealed significant effects of survey month, vineyard site, and year on adult abundance in sweep and trap surveys. Spittlebug adults were present in the vineyards from April until December, with the greatest number of adults by sweep net in May or June, whereas adults on traps peaked between July and November. Analysis of natural infectivity in groups of field-collected spittlebug adults showed significant difference in transmission rates among months. Spittlebugs successfully transmitted Xylella fastidiosa (Wells) (Xanthomonadales: Xanthomonadaceae) to potted grapevines between July and December. The greatest risk of X. fastidiosa transmission by P. spumarius was in December (60%) followed by October (30%). However, the infectivity patterns of the meadow spittlebug did not align with the historical paradigm of California North Coast PD. We discuss alternative hypotheses in which P. spumarius could play a role in the epidemiology of this disease.

Ex vivo infection of canine and ovine placental explants with Trypanosoma cruzi and Toxoplasma gondii: differential activation of NF kappa B signaling pathways

Chagas disease and toxoplasmosis, caused by Trypanosoma cruzi and Toxoplasma gondii, respectively, are important zoonotic diseases affecting humans, companion animals, and livestock, responsible for major health and economic burden. Both parasites can be transmitted vertically in different mammalian species through the placenta. Of note, the transmission rate of T. cruzi is low in dogs, whereas that of T. gondii is high in sheep. The probability of congenital infection depends on complex parasite-host interactions; parasite factors, maternal and fetal immune responses and placental responses all have a role in infection establishment. Since the innate immune response is regulated, at least partially, by NF-κB signaling pathways, our main objective was to determine the effect of ex vivo infection of canine (CPE) and ovine (OPE) placental explants with both parasites, on the activation of canonical and non-canonical NF-κB pathways and its relation to infection. Here, we show that T. cruzi activates both the NF-κB canonical and non-canonical pathways in CPE and OPE, unlike T. gondii, that activates only the canonical pathway in CPE and has no effect on the non-canonical pathway in both explants. Moreover, the inhibition of either or both NF-κB pathways increases the DNA load of T. cruzi in both explants, modulates, on the other hand, T. gondii infection in a differential fashion. Overall, we conclude that the differential modulation of the NF-κB pathways by both pathogens in placental explants might explain, at least partially, the differences in transmission rates of T. cruzi and T. gondii in different mammalian species.

Relationships of virus titers and transmission rates among sympatric and allopatric virus isolates and thrips vectors support local adaptation

Plant viruses rely on insect vectors for transmission among plant hosts, but many of the specifics of virus-vector interactions are not fully understood. Thrips tabaci, which transmits Tomato spotted wilt virus (TSWV) in a persistent and propagative manner, varies greatly in its ability to transmit different isolates of TSWV. Similarly, TSWV isolates are transmitted at different efficiencies by different populations of T. tabaci. This study characterizes differences in virus titers in the vector among TSWV isolate-T. tabaci isoline pairings in relation to differences in transmission rates, and demonstrates that although transmission rates were higher for sympatric than allopatric TSWV isolate-T. tabaci isoline pairings, virus titers in the thrips vector were significantly lower in the sympatric pairings. Results further demonstrate that TSWV titers in the vector were unrelated to virus titers in the leaf tissue from which they acquired the virus and provide evidence for the importance of specific vector-virus interactions and local adaptation in determining transmission efficiency of TSWV by T. tabaci.

Heterogeneous susceptibility to rotavirus infection and gastroenteritis in two birth cohort studies: Parameter estimation and epidemiological implications

Cohort studies, randomized trials, and post-licensure studies have reported reduced natural and vaccine-derived protection against rotavirus gastroenteritis (RVGE) in low- and middle-income countries. While susceptibility of children to rotavirus is known to vary within and between settings, implications for estimation of immune protection are not well understood. We sought to re-estimate naturally-acquired protection against rotavirus infection and RVGE, and to understand how differences in susceptibility among children impacted estimates. We re-analyzed data from studies conducted in Mexico City, Mexico and Vellore, India. Cumulatively, 573 rotavirus-unvaccinated children experienced 1418 rotavirus infections and 371 episodes of RVGE over 17,636 child-months. We developed a model that characterized susceptibility to rotavirus infection and RVGE among children, accounting for aspects of the natural history of rotavirus and differences in transmission rates between settings. We tested whether model-generated susceptibility measurements were associated with demographic and anthropometric factors, and with the severity of RVGE symptoms. We identified greater variation in susceptibility to rotavirus infection and RVGE in Vellore than in Mexico City. In both cohorts, susceptibility to rotavirus infection and RVGE were associated with male sex, lower birth weight, lower maternal education, and having fewer siblings; within Vellore, susceptibility was also associated with lower socioeconomic status. Children who were more susceptible to rotavirus also experienced higher rates of rotavirus-negative diarrhea, and higher risk of moderate-to-severe symptoms when experiencing RVGE. Simulations suggested that discrepant estimates of naturally-acquired immunity against RVGE can be attributed, in part, to between-setting differences in susceptibility of children, but result primarily from the interaction of transmission rates with age-dependent risk for infections to cause RVGE. We found that more children in Vellore than in Mexico City belong to a high-risk group for rotavirus infection and RVGE, and demonstrate that unmeasured individual- and age-dependent susceptibility may influence estimates of naturally-acquired immune protection against RVGE.

A charge-transfer resistance model and Arrhenius activation analysis for hydrogen ion transmission across single-layer graphene

Transmission rates for protons and deuterons across single-layer graphene embedded in Nafion | graphene | Nafion sandwich structures are measured as a function of temperature in electrochemical hydrogen pump cells. Rates of ion transmission through graphene are obtained in the form of area-normalized ion-transfer resistances, and are interpreted in terms of ion-exchange current densities and standard heterogeneous ion-transfer rate constants. An encounter pre-equilibrium model for the ion-transfer step is then used to provide rate constants for the fundamental microscopic step of ion (proton or deuteron) transmission across graphene. Application of this rate model to interpret variable-temperature data on proton and deuteron transmission rates provides values for the activation energy and pre-exponential factor for the fundamental ion transmission step across graphene. Activation energies obtained from the Arrhenius plots for proton and deuteron transmission are as follows; for proton, Eact = 48 ± 2 kJ/mole (0.50 ± 0.02 eV) and for deuteron, Eact = 53 ± 5 kJ/mole (0.55 ± 0.05 eV). The difference between these two values of approximately 5 kJ/mole is in good agreement with the expected difference in vibrational zero-point energies for OH and O-D bonds, albeit with some uncertainty given the uncertainties in the activation energy values. Pre-exponential frequency factor values of 8.3 ± 0.4 × 1013 s−1 and is 4.7 ± 0.5 × 1013 s−1 were obtained for proton and deuteron transmission respectively across graphene. These pre-factor values are both quite large, on the order of the values predicted from the Eyring – Polanyi equation with a transmission coefficient near one. The ratio of 1.8 for the rate pre-factors (H/D) is in reasonable agreement with the value of 1.3 for the ratio of bond vibrational frequencies for OH and O-D stretching, respectively. Taken together, these data support a model in which proton and deuteron transmission across graphene are largely adiabatic processes for which the differences in transmission rate at room temperature are due largely to differences in activation energies.

Potential of Aedes aegypti populations in Madeira Island to transmit dengue and chikungunya viruses

BackgroundAedes spp. mosquitoes mainly transmit the arboviruses dengue virus (DENV) and chikungunya virus (CHIKV) in urban areas, causing a severe public health problem. In 2012–2013, a major dengue outbreak occurred on Madeira Island where the mosquito Aedes aegypti was the only vector. Up to now, the competence of Ae. aegypti populations from Madeira to transmit DENV or CHIKV remains unknown. This study aimed to assess experimentally the ability of Ae. aegypti populations from Madeira to transmit these viruses.ResultsBy orally exposing mosquitoes to CHIKV (NC/2011-568) and DENV-2 (Bangkok), the vector competence of two field-collected Ae. aegypti populations, i.e. Funchal and Paúl do Mar, was evaluated. We found that both populations were similarly infected and ensured the dissemination and transmission of CHIKV at the same rates. With DENV-2, viral dissemination was significantly higher in the Funchal population compared to Paúl do Mar. We found no significant differences in transmission rates between populations.ConclusionsTo our knowledge, this study has demonstrated for the first time the ability of temperate European Ae. aegypti populations from Madeira to transmit DENV and CHIKV. As our results suggest, there is a potential risk for the local transmission of DENV and CHIKV if introduced to Madeira or continental Europe where Aedes albopictus is present. Our results highlight the need for continuing vector surveillance and control on Madeira Island to future-proof the Island against mosquito-borne epidemics.

Inferring within-herd transmission parameters for African swine fever virus using mortality data from outbreaks in the Russian Federation.

SummaryMortality data are routinely collected for many livestock and poultry species, and they are often used for epidemiological purposes, including estimating transmission parameters. In this study, we infer transmission rates for African swine fever virus (ASFV), an important transboundary disease of swine, using mortality data collected from nine pig herds in the Russian Federation with confirmed outbreaks of ASFV. Parameters in a stochastic model for the transmission of ASFV within a herd were estimated using approximate Bayesian computation. Estimates for the basic reproduction number varied amongst herds, ranging from 4.4 to 17.3. This was primarily a consequence of differences in transmission rate (range: 0.7–2.2), but also differences in the mean infectious period (range: 4.5–8.3 days). We also found differences amongst herds in the mean latent period (range: 5.8–9.7 days). Furthermore, our results suggest that ASFV could be circulating in a herd for several weeks before a substantial increase in mortality is observed in a herd, limiting the usefulness of mortality data as a means of early detection of an outbreak. However, our results also show that mortality data are a potential source of data from which to infer transmission parameters, at least for diseases which cause high mortality.

Modeling the Impact of Retention Interventions on Mother-to-Child Transmission of HIV: Results From INSPIRE Studies in Malawi, Nigeria, and Zimbabwe.

Six implementation research studies in Malawi, Nigeria, and Zimbabwe tested approaches for improving retention in care among women living with HIV. We simulated the impact of their interventions on the probability of HIV transmission during pregnancy and breastfeeding. A computer-based state-transition model was developed to estimate the impact of the retention interventions. Patient-level data from the 6 studies were aggregated and analyzed, and weighted averages of mother-to-child transmission (MTCT) of HIV probabilities were presented. The average MTCT probability of the more successful interventions was applied to national estimates to calculate potential infections averted if these interventions were taken to scale. Among the total cohort of 5742 HIV-positive women, almost 80% of all infant infections are attributed to the roughly 20% of HIV-positive pregnant and breastfeeding women not retained on antiretroviral therapy. Higher retention in the arms receiving interventions resulted in an overall lower estimated MTCT probability of 9.9% compared with 12.3% in the control arms. In the 2 studies that showed a statistically significant effect, Prevention of MTCT Uptake and Retention (PURE) and Mother Mentor (MoMent), the difference in transmission rates between intervention and control arms was 4.1% and 7.3%, respectively. Scaling up retention interventions nationally in the 3 countries could avert an average of almost 3000 infant infections annually. Linking HIV-positive pregnant women to antiretroviral therapy and retaining them is essential for addressing the remaining gaps and challenges in HIV/AIDS care and the elimination of MTCT. At national level, even modest improvements in retention translates into large numbers of infant infections averted.

Influence of Citrus Source and Test Genotypes on Inoculations with Candidatus Liberibacter asiaticus

Assessments of the resistance of citrus germplasm to huanglongbing (HLB) can be expedited by inoculating plants under laboratory or greenhouse settings with the HLB bacterium, Candidatus Liberibacter asiaticus (CLas). Consistent rapid screening is critical to efficiently assess disease resistance among plant materials; however, a number of factors may govern the efficacy of such inoculations. Despite the rapidity at which HLB can spread in a grove, it often takes 8 to 10 months for high levels of CLas and HLB symptoms to develop even in highly susceptible sweet orange. Therefore, two experiments were conducted to assess factors that might influence efficiency in screening for HLB resistance. In one experiment, three test citrus genotypes (‘Kuharske’, previously shown to be HLB resistant; rough lemon, previously shown to be HLB tolerant; and ‘Valencia’, HLB susceptible) were bud grafted using CLas-infected buds from four different source genotypes. All bud source genotypes had similar levels of CLas titer, but citron, rough lemon, and Volkamer lemon were hypothesized to be better bud inoculum sources as they are more tolerant of HLB than ‘Valencia’. Among the three test genotypes over all sources of infected buds, inoculations of ‘Kuharske’ resulted in lower CLas titers and fewer HLB symptoms than inoculations of rough lemon or ‘Valencia’. Inoculations of rough lemon resulted in higher CLas titers and more pronounced HLB symptoms when it was inoculated using infected buds from rough lemon or ‘Valencia’. Grafting ‘Valencia’ with infected buds from Volkamer lemon resulted in less disease than when ‘Valencia’ was grafted with infected citron, rough lemon, or ‘Valencia’ buds. Overall, these results suggest that the source of CLas-infected buds used to graft-inoculate some genotypes will influence disease development. Trunk cross-sectional area increase for the year following infection was 3× higher in ‘Kuharske’ and rough lemon, compared with ‘Valencia’. ‘Kuharske’ had very low levels of CLas (30 CLas/µg DNA), whereas ‘Valencia’ (43,000 CLas/µg DNA) and rough lemon (6700 CLas/ µg DNA) had relatively high levels. As an alternative to graft-inoculating plants with CLas-infected buds, plants can be subjected to infestations of CLas-infected Asian citrus psyllid (ACP) as occurs naturally. Of interest is if transmission rates of CLas and the development of HLB in a genotype are greater when the ACP have been feeding on the same host genotype. An experiment was therefore conducted to assess transmission of CLas by ACP reared on CLas-infected rough lemon to five different genotypes (‘Carrizo’, ‘Flame’ grapefruit, rough lemon, ‘Temple’, and ‘Valencia’). These assessments were made using a detached leaf assay recognized as a faster method of gauging transmission rates of CLas than using whole plants. Higher percentages of ACP died when they were transferred from infected rough lemon to healthy ‘Carrizo’, and lower percentages died when they were transferred to rough lemon or ‘Flame’. However, CLas transmission by infected ACP occurred to at least some leaves of each genotype in each of the five different assays, with 70% or more leaves of each genotype becoming infected in at least one assay. Over all assays, there was relatively little variation among genotypes in the percentage of leaves becoming CLas infected and in the titer of CLas developing in infected leaves. However, there were relatively large differences in transmission rates among individual assays unrelated to differences among test genotypes. Because of the rapidity of the detached leaf assay, efforts are merited to improve consistency of this inoculation method.