Aviation passenger screening has been used worldwide to mitigate the translocation risk of SARS-CoV-2. We present a model that evaluates factors in screening strategies used in air travel and assess their relative sensitivity and importance in identifying infectious passengers. We use adapted Monte Carlo simulations to produce hypothetical disease timelines for the Omicron variant of SARS-CoV-2 for travelling passengers. Screening strategy factors assessed include having one or two RT-PCR and/or antigen tests prior to departure and/or post-arrival, and quarantine length and compliance upon arrival. One or more post-arrival tests and high quarantine compliance were the most important factors in reducing pathogen translocation. Screening that combines quarantine and post-arrival testing can shorten the length of quarantine for travelers, and variability and mean testing sensitivity in post-arrival RT-PCR and antigen tests decrease and increase with the greater time between the first and second post-arrival test, respectively. This study provides insight into the role various screening strategy factors have in preventing the translocation of infectious diseases and a flexible framework adaptable to other existing or emerging diseases. Such findings may help in public health policy and decision-making in present and future evidence-based practices for passenger screening and pandemic preparedness.

The SARS-CoV-2 is transmitted not only through coughing, but also through breathing, speaking or singing. We perform direct numerical simulations of the turbulent transport of potentially infectious aerosols in short conversations, involving repetitive phrases separated by quiescent intervals. We estimate that buoyancy effects due to droplet evaporation are small, and neglect them. A two-way conversation is shown to significantly reduce the aerosol exposure compared with a relative monologue by one person and relative silence of the other. This is because of the ‘cancelling’ effect produced by the two interacting speech jets. Unequal conversation is shown to significantly increase the infection risk to the person who talks less. Interestingly, a small height difference is worse for infection spread, due to reduced interference between the speech jets, than two faces at the same level. For small axial separation, speech jets show large oscillations and reach the other person intermittently. We suggest a range of lateral separations between two people to minimize transmission risk. A realistic estimate of the infection probability is provided by including exposure through the eyes and mouth, in addition to the more common method of using inhaled virions alone. We expect that our results will provide useful inputs to epidemiological models and to disease management.

This study investigated the characteristics of transmission routes of COVID-19 cluster infections (⩾10 linked cases within a short period) in Gangwon Province between 22 February 2020 and 31 May 2021. Transmission routes were divided into five major categories and 35 sub-categories according to the relationship between the infector and the infectee and the location of transmission. A total of 61 clusters occurred during the study period, including 1741 confirmed cases (55.7% of all confirmed cases (n = 3125)). The the five major routes of transmission were as follows: ‘using (staying in) the same facility (50.7%), ‘cohabiting family members’ (23.3%), ‘social gatherings with acquaintances’ (10.8%), ‘other transmission routes’ (7.0%), and ‘social gatherings with non-cohabiting family members/relatives’ (5.5%). For transmission caused by using (staying in) the same facility, the highest number of confirmed cases was associated with churches, followed by medical institutions (inpatient), sports facilities, military bases, offices, nightlife businesses, schools, restaurants, day-care centres and kindergarten, and service businesses. Our analysis highlights specific locations with frequent transmission of infections, and transmission routes that should be targeted in situations where adherence to disease control rules is difficult.

Fascioliasis is a zoonotic disease caused by liver flukes transmitted by freshwater lymnaeid snails. Donkey and horse reservoir roles have been highlighted in human endemic areas. Liver fluke infection in mules has received very limited research. Their role in disease transmission, epidemiological importance and Fasciola hepatica pathogenicity are studied for the first time. Prevalence was 39.5% in 81 mules from Aconcagua, and 24.4% in 127 from Uspallata, in high-altitude areas of Mendoza province, Argentina. A mean amount of 101,242 eggs/mule/day is estimated. Lymnaeids from Uspallata proved to belong to ribosomal DNA internal transcribed spacer (ITS) markers ITS-1 and ITS-2 combined haplotype 3C of Galba truncatula. These lymnaeids were experimentally susceptible to infection by egg miracidia from mules. Infectivity, number of cercariae/snail and shedding period fit the enhanced F. hepatica/G. truncatula transmission pattern at very high altitude. This indicates that the mule is able to maintain the F. hepatica cycle independently. Individual burdens of 20 and 97 flukes were found. Mule infection susceptibility is intermediate between donkey and horse, although closer to the latter. Anatomo-pathology and histopathology indicate that massive infection may cause mule death. Haematological value decreases of red blood cells, haemoglobin, leucocytes and lymphocytes indicate anaemia and strong immunosuppression. Strongly increased biochemical marker values indicate liver function alterations. The mule probably played a role in the past exchanges with Chile and Bolivia through Mendoza province. Evidence suggests that mules could contribute to the spread of both F. hepatica and G. truncatula to human fascioliasis-endemic areas in these countries.

A recent countrywide MRSA spa-type 1081 outbreak in The Netherlands predominantly affected nursing homes, generating questions on how infection spreads within and between nursing homes despite a low national prevalence. Since the transfer of residents between nursing homes is uncommon in The Netherlands, we hypothesized that staff exchange plays an important role in transmission. This exploratory study investigated the extent of former (last 2 years) and current staff exchange within and between nursing homes in The Netherlands. We relied on a questionnaire that was targeted towards nursing-home staff members who had contact with residents. We found that 17·9% and 12·4% of the nursing-home staff formerly (last 2 years) or currently worked in other healthcare institutes besides their job in the nursing home through which they were selected to participate in this study. Moreover, 39·7% of study participants worked on more than one ward. Our study shows that, in The Netherlands, nursing-home staff form a substantial number of links between wards within nursing homes and nursing homes are linked to a large network of healthcare institutes through their staff members potentially providing a pathway for MRSA transmission between nursing homes and throughout the country.

Estimation of the true incidence of tuberculosis (TB) is challenging. The approach proposed by Styblo in 1985 is known to be inaccurate in the modern era where there is widespread availability of treatment for TB. This study re-examines the relationship of incidence to prevalence and other disease indicators that can be derived from surveys. We adapt a simple, previously published model that describes the epidemiology of TB in the presence of treatment to investigate a revised ratio-based approach to estimating incidence. We show that, following changes to treatment programmes for TB, the ratio of incidence to prevalence reaches an equilibrium value rapidly; long before other model indicators have stabilized. We also show that this ratio relies on few parameters but is strongly dependent on, and requires knowledge of, the efficacy and timeliness of treatment.

Weather conditions and social contact patterns provide some clues to understanding year-round influenza epidemics in the tropics. Recent studies suggest that contact patterns may direct influenza transmission in the tropics as critically as the aerosol channel in temperate regions. To examine this argument, we analysed a representative nationwide survey dataset of contact diaries with comprehensive weather data in Taiwan. Methods we used included model-free estimated relative changes in reproduction number, R 0; relative changes in the number of contacts; and model-based estimated relative changes in mean contacts using zero-inflated negative binomial regression models. Overall, social contact patterns clearly differ by demographics (such as age groups), personal idiosyncrasies (such as personality and happiness), and social institutions (such as the division of weekdays and weekend days). Further, weather conditions also turn out to be closely linked to contact patterns under various circumstances. Fleeting contacts, for example, tend to diminish when it rains hard on weekdays, while physical contacts also decrease during weekend days with heavy rain. Frequent social contacts on weekdays and under good weather conditions, including high temperature and low absolute humidity, all might facilitate the transmission of infectious diseases in tropical regions.

Climate change has already provoked a northward shift in the geographic range of many bird species, and current climate projections favour the modification of avian distributions and migratory routes. Given that wild birds are recognised as pathogen-dispersing agents, there is concern that changes in migrant ranges and movement patterns will increase the frequency of bird-borne pathogens reaching Northern areas, such as Canada. Furthermore, climate change will likely affect vector, pathogen, and reservoir ecology, which could contribute to changes in the range limits, the intensity of disease transmission and, under some circumstances, the risk of emergence and re-emergence of pathogens affecting commercial poultry.

However, the role of wild birds in the perpetuation of disease is unclear. Even if climate change increases the introduction of zoonotic and bird-borne pathogens into Canada, it is difficult to predict whether this will increase the occurrence of diseases in poultry. It is likely that outbreaks will become more unpredictable, which will complicate efforts to identify periods and areas of high risk. Efforts to manage and control these events in the face of climate change will require proper biosecurity measures, in addition to more consistent surveillance of sentinel and high-risk carrier species to avert the potential risk of diseases dispersing into Canada.

The use of shared common water points (WPs) and grazing points (GPs) at two different levels of administrative aggregation (village and kebelle) in a region of the Highlands of Ethiopia was explored by means of a questionnaire survey and social network analysis. Despite GPs being more abundant than WPs (208 and 154, respectively), individual GPs provide more contact opportunities for animals. There was great variability in the contact structure of the selected villages within kebelles for both networks, with this variability being higher in the GP networks for each kebelle. Contrary to the commonly held view that WPs are critical for the potential transmission of infectious diseases, intervention at GPs in the Ethiopian Highlands may have greater impact on contacts and thereby opportunities for transmission of infectious diseases between flocks. Some villages appear naturally at much lower risk of introducing disease. These findings could help the design of surveillance and control activities for directly transmitted infectious diseases.

Background/Objective. Multiple factors affect schistosomiasis transmission in distributed meta-population systems including age, behaviour, and environment. The traditional approach to modelling macroparasite transmission often exploits the ‘mean worm burden’ (MWB) formulation for human hosts. However, typical worm distribution in humans is overdispersed, and classic models either ignore this characteristic or make ad hoc assumptions about its pattern (e.g., by assuming a negative binomial distribution). Such oversimplifications can give wrong predictions for the impact of control interventions. Methods. We propose a new modelling approach to macro-parasite transmission by stratifying human populations according to worm burden, and replacing MWB dynamics with that of ‘population strata’. We developed proper calibration procedures for such multi-component systems, based on typical epidemiological and demographic field data, and implemented them using Wolfram Mathematica. Results. Model programming and calibration proved to be straightforward. Our calibrated system provided good agreement with the individual level field data from the Msambweni region of eastern Kenya. Conclusion. The Stratified Worm Burden (SWB) approach offers many advantages, in that it accounts naturally for overdispersion and accommodates other important factors and measures of human infection and demographics. Future work will apply this model and methodology to evaluate innovative control intervention strategies, including expanded drug treatment programmes proposed by the World Health Organization and its partners.

We developed an individual-based (IB) model to explore the stochastic attributes of state transitions, the heterogeneity of the individual interactions, and the impact of different network structure choices on the poliovirus transmission process in the context of understanding the dynamics of outbreaks. We used a previously published differential equation-based model to develop the IB model and inputs. To explore the impact of different types of networks, we implemented a total of 26 variations of six different network structures in the IB model. We found that the choice of network structure plays a critical role in the model estimates of cases and the dynamics of outbreaks. This study provides insights about the potential use of an IB model to support policy analyses related to managing the risks of polioviruses and shows the importance of assumptions about network structure.

Most cases of measles in Australia are associated with travel or acquired from travellers from overseas. This study presents a series of three secondary cases of measles acquired through contact with a case of infectious measles acquired in China. Two of the cases were fully immunized siblings sitting eight rows behind the index case on a 4½-h flight from Singapore. The third case was acquired in the airport where the index case was in transit. The report highlights the travel-associated risk of measles and discusses the heredity of vaccine-induced measles immunity.

This article studies how our understanding of population-level disease transmission has evolved over time. The main question is: what happens to ‘facts’ in the course of their life history? The concept of life history captures the process that shapes the facts of disease transmission, mobilizes them via mathematical and graphical representations, and allows them to evolve and change over time. Hence, this concept provides continuity from knowledge production to utilization. Life history is developed through phases in the ‘lives’ of ‘facts’: birth and youth, adulthood and reproductive years, and old age. The life-history approach consists of a set of ‘facts’ binding together knowledge of a disease, its routes of transmission, and the susceptibility of the exposed population; it thus provides an adequate framework to explore the complex nature of population-level disease transmission. The analytical focus of this article is concerned with how these ‘facts’ are disseminated via model-based or mathematical representations. Just as life histories are stories full of interactions, surprises and struggles, this article highlights the underlying contingencies in the dissemination and accumulation of factual knowledge.

An in vitro feeding method using rabbit or cattle skin membranes, applied successfully to all stages (larvae, nymphae and adults) of the ixodid tick, Amblyomma variegatum, is described. The feeding apparatus consisted of a blood container with a membrane placed on top of a tick containment unit. A carbon dioxide atmosphere of between 5 and 10% and a temperature of 37 °C were used as stimulants for the attachment of the ticks. High CO2 concentrations in the atmosphere improved the feeding success of all instars. The effect of anticoagulation methods for the bloodmeal was investigated, and heparinized blood was found to be the most suitable for tick feeding. When the bloodmeal was replaced by tissue culture medium for feeding nymphs the subsequent moulting success was reduced. Adult ticks of both sexes remained attached for up to 16 days, until completion of their bloodmeals. All stages of the tick fed on whole blood in the artificial feeding system and all reached engorged weights less than those achieved by control ticks fed on experimental animals. A large proportion of ticks, fed artificially on whole blood, moulted or laid eggs successfully. The method was successfully applied for the transmission of Theileria mutans and Cowdria ruminantium to cattle.

Leukoreduction, filtering white blood cells from transfusion blood, effectively avoids leukocyte-related complications of blood transfusion. The technology has proven its relative cost-effectiveness for specific patient populations. With the advent of variant Creutzfeldt–Jakob disease, a transmittable spongiform encephalopathy caused by mad cow disease (bovine spongiform encephalopathy), the hard hit United Kingdom introduced universal leukoreduction for all patients as a precaution for transmission of prions in 1999. This costly policy was followed by many other countries, in the absence of much evidence of an actual health problem or of a more than presumed effectiveness of leukoreduction in preventing prion transmission. The core problem proved to be legal. The blood banks are legally accountable for blood safety. This accountability is absolute, based on avoidance of all possible risks, regardless of costs. This strategy leads to inefficiencies in health care: (i) blood safety management is guided by available rather than cost-effective technology, and (ii) private insurance premiums for civil liability are sharply increasing, while they are in no way related to the expected returns and the high and increasing blood safety. A rational safety policy is to be optimal, taking into account costs and effects of the safety procedures. This issue will need an open discussion with the general public of the real risks and a clear and unambiguous definition of proportionality in the precautionary principle, based on the European law.

Summary

Introduction: We tested the hypothesis that repeated autoclaving removes protein deposits from the classic laryngeal mask airway (LMA). Methods: Twenty previously used LMAs were hand washed, machine washed, dried, autoclaved and randomly allocated into four equal-sized groups for repeat autoclaving on 0 (control), 1, 2 and 3 occasions. After the final autoclave cycle, the LMAs were immersed in a protein-staining solution, rinsed, dried and a high-resolution digital image taken of the dorsal and ventral surfaces. The severity of staining was scored by two blinded observers. Results: All LMAs were stained. There was no reduction in staining with repeat autoclaving. Conclusions: Repeat autoclaving does not remove protein deposits from the LMA.

Introduction. Beginning in 1994, vanilla vines grown under shade houses in Reunion Island have developed disorders mainly due to the cymbidium mosaic potexvirus (CymV) and potyviruses. To reduce damage and avoid viral epidemics, we considered developing a vanilla nursery to supply farmers with virus-free plant material and to provide prophylactic advice. Accordingly, we determined the relationship between symptoms on vanilla leaves and viral diagnosis. We also determined the temporal and spatial distribution patterns of viral diseases. Materials and methods. Symptom assessment and serological tests were carried out on vanilla leaves (Vanilla fragrans) at various times. The relationship between symptoms and viral infection data was analyzed with Statistica software. Spatial distribution patterns of infected plants were generated with two-dimensional distance class analysis (2DClass). Results and discussion. Results showed that symptoms do not correlate well with serological diagnosis. Plants in all shade houses in the survey were infected mainly by CymV which spreads in the row according to cultural practices. Potyviruses could be transmitted both by insect vectors and mechanically, but for the latter case less efficiently than CymV. Conclusion. Results from this study can be used to develop control measures, including the production of healthy planting materials to manage plant disease epidemics. Further studies will involve the characterization of vanilla potyviruses so that reliable serological techniques and better molecular tools can be developed.