The host contact network structure results from the movement and behaviour of hosts (e.g. degree of sociability; vagility and greater or lesser fidelity of shelters), which can generate heterogeneity in the transmission of parasites and influence the parasitic burden of individual hosts. In the current study, we tested the hypothesis that the burdens of Gigantolaelaps oudemansi mites are related to the characteristics of the transmission networks of individuals of Oecomys paricola, a solitary rodent. The study was carried out in a savannah habitat in north-eastern Brazil. In the dry season, the rodent network presented sub-groups of rodent individuals interacting with each other, whereas in the wet season, no modules were formed in the network. Mite burden was positively related to the number of connections that an individual host had with other host individuals in the dry season. The pairwise absolute difference between the mean mite burdens among individual rodents was negatively correlated with the similarities of node interactions. No relationships were observed during the wet season. There was a higher heterogeneity of mite burden among hosts in the dry season compare to that in the wet season. In solitary species, spatial organization may show seasonal variation, causing a change in the opportunities of host contacts, thereby influencing the transmission and dispersion of their ectoparasite burdens.

Vaccination has reduced the disease burden of vaccine-preventable diseases. However, the extent to which seasonal cycles of immunity could influence vaccine-induced immunity is not well understood. A national cross-sectional serosurveillance study performed in the Netherlands (Pienter-2) yielded data to investigate whether season of vaccination was associated with antibody responses induced by DT-IPV (diphtheria, tetanus and poliomyelitis), MMR (measles, mumps and rubella) and meningococcus C (MenC) vaccines in children. In total, 434 children met the inclusion criteria to study DT-IPV immunity, 811 for MMR and 311 for MenC. Differences in log(antibody levels) by season of vaccination were investigated with linear multivariable regression analyses. Seroconversion rates varied according to season of vaccination for rubella (90% of autumn-vaccinated children vs. 99% of winter-vaccinated had concentrations above cut-off levels). Summer-vaccinated boys showed a slower decline of tetanus antibodies (6% per month), in comparison with winter-vaccinated boys. In conclusion, season of vaccination showed little association with immunological protection. However, a number of associations were seen with a P-value of about 0.03; and adding data from a just-completed nationwide serological study might add more power to the current study. Further immunological and longitudinal investigations could help understand the mechanisms of seasonal influence in vaccine-induced responses.

The goal of this article is to demonstrate the value of a global perspective on pandemics for understanding how global pandemics caused by novel viruses can unfold. Using the example of the 1918 influenza pandemic, two factors that were central to the evolving pattern of global pandemic waves, connectivity and seasonality, are explored. Examples of the influences of these factors on pandemic waves in different locations are presented. Viewing the 1918 pandemic through the lens of compartmental models of infectious diseases, our analysis suggests that connectivity played a dominant role in the initial stages. With the passage of time and the progressive infection and consequent immunization of more and more people, however, the role of seasonality increased in importance, ultimately becoming the driving force behind the emergence of future waves of infection. Implications of these observations for pandemics caused by novel viruses such as the ongoing COVID-19 pandemic are discussed.

Purpose: The novel coronavirus (severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)) first appeared in Wuhan, China, in December 2019, and rapidly spread across the globe. Since most respiratory viruses are known to show a seasonal pattern of infection, it has been hypothesised that SARS-CoV-2 may be seasonally dependent as well. The present study looks at a possible effect of atmospheric temperature, which is one of the suspected factors influencing seasonality, on the evolution of the pandemic. Basic procedures: Since confirming a seasonal pattern would take several more months of observation, we conducted an innovative day-to-day micro-correlation analysis of nine outbreak locations, across four continents and both hemispheres, in order to examine a possible relationship between atmospheric temperature (used as a proxy for seasonality) and outbreak progression. Main findings: There was a negative correlation between atmospheric temperature variations and daily new cases growth rates, in all nine outbreaks, with a median lag of 10 days. Principal conclusions: The results presented here suggest that high temperatures might dampen SARS-CoV-2 propagation, while lower temperatures might increase its transmission. Our hypothesis is that this could support a potential effect of atmospheric temperature on coronavirus disease progression, and potentially a seasonal pattern for this virus, with a peak in the cold season and rarer occurrences in the summer. This could guide government policy in both the Northern and Southern hemispheres for the months to come.

Nuestro objetivo es estudiar las estrategias de uso del espacio por parte de sociedades humanas móviles en un paisaje andino de Patagonia caracterizado por una marcada heterogeneidad topográfica, climática y ecológica (localidad de Barrancas-Buta Ranquil, provincia del Neuquén, Argentina). Inicialmente, se analiza la estructura del paisaje desde una perspectiva biogeográfica, desarrollando un modelo de estacionalidad mediante sistemas de información geográfica. Nuestro enfoque distribucional combina una prospección sistemática para caracterizar la estructura espacial del registro en superficie y evidencias que han sido obtenidas bajo otras estrategias de muestreo. Sobre la base de la distribución de artefactos líticos y cerámicos y de motivos rupestres, se evalúan patrones de intensidad ocupacional, diversidad funcional y circulación de información en sectores del espacio con propiedades biogeográficas diferentes. Los resultados sugieren una delimitación funcional del espacio en escala temporal promediada, en la cual los espacios intermedios habrían funcionado como lugares centrales desde donde se articulan movimientos logísticos hacia otros sectores del paisaje. Dado que la unidad de muestreo captura variación biogeográfica que se expresa en forma regional más amplia, el modelo de uso del espacio propuesto es relevante para la comprensión de la arqueología del noroeste de Patagonia en general.

Wildlife species are often host to a diversity of parasites, but our knowledge of their diversity and ecology is extremely limited, especially for reptiles. Little is known about the host-parasite ecology of the Australian lizard, the King's skink (Egernia kingii). In spring of 2015, we carried out a field-based study of a population of King's skinks on Penguin Island (Western Australia). We documented five species of parasites, including two ectoparasitic mites (an undescribed laelapid mite and Mesolaelaps australiensis), an undescribed coccidia species, and two nematode species (Pharyngodon tiliquae and Capillaria sp.). The laelapid mite was the most abundant parasite, infesting 46.9% of the 113 captured lizards. This mite species increased in prevalence and abundance over the course of the study. Infection patterns of both mites varied with lizard life-stage; sub-adults were more commonly infested with laelapid mites than adults or juveniles, and sub-adults and adults were infested by more laelapid mites than juveniles. By contrast, adults had a higher prevalence of M. australiensis than juveniles or sub-adults. Among the gastrointestinal parasites, P. tiliquae was relatively common among the sampled lizards (35.3%). These results give new important information about reptiles as parasite hosts and what factors influence infection patterns.

For species with environmental sex determination, understanding the relationship between reproduction and environmental factors is important for predicting their reproductive output. Here, we study intra-annual variation in green turtle nesting during the 2010–2016 seasons at Penang Island (5°16′28″–5°28′15″N 100°10′52″–100°11′55″E), Malaysia. The additive modelling on a monthly-basis number of nests shows that fluctuation in the number of nests relates to temperature in addition to month of year, rather than precipitation. The number of nests tended to be higher in response to higher temperature during March–July, whereas the lower temperature during August–February also tended to result in a relatively higher number of nests. Concentration of nests during March–July resulted from a shorter inter-nesting interval during warm temperatures, whereas relatively low temperatures may homogenize the temporal distribution of the number of nests. This study provides fundamental information for green turtle nesting seasonality in response to environmental change.

The aim of the present study is to evaluate the seasonal pattern of recurrences and the concordance among first episode (index episode) versus the subsequent recurrences in a sample of 210 patients affected by mood disorders, referred to the Mood Disorder Unit of San Raffaele Hospital. The most depressive recurrences are in spring for unipolar subjects and in fall for bipolars. Manic episodes are more frequent in summer. Patients presented a high concordance rate between the first and the second episode, female patients were more concordant than male subjects, and patients with low cycle of illness (one episode every six or more years) were the most concordant ones.

Although genetic and environmental factors operating before or around the time of birth have been demonstrated to be relevant to the aetiology of the major psychoses, a seasonal variation in the rates of admission of such patients has long been recognised. Few studies have compared first and readmissions. This study examined for seasonal variation of admission in the major psychoses, and compared diagnostic categories by admission status. Patients admitted to Irish psychiatric inpatient facilities between 1989 and 1994 with an ICD-9/10 diagnosis of schizophrenia or affective disorder were identified from the National Psychiatric Inpatient Reporting System (NPIRS). The data were analysed using a hierarchical log linear model, the chi-square test, a Kolmogorov-Smirnov (KS) type statistic, and the method of Walter and Elwood. The hierarchical log linear model demonstrated significant interactions between the month of admission and admission order (change in scaled deviance 28.77, df = 11, P < 0.003). Both first admissions with mania, and readmissions with bipolar affective disorder exhibited significant seasonality. In contrast, only first admissions with schizophrenia showed significant seasonal effects. Although first admissions with mania and readmissions with bipolar disorder both show seasonality, seasonal influences appear to be more relevant to onset of schizophrenia than subsequent relapse.

We compared the rate of DST non-suppression in two samples of 26 Brazilian and 26 Belgian female depressive patients, matched for age, diagnostic subtype and severity of depression. This rate was significantly lower in São Paulo than in Liège (P = 0.04). The differences observed in DST can be explained by the complexity of familial, personal and clinical factors. A role of a latitude effect through melatonin secretion on adrenocortical function of depressed patients is also suggested.

Far from being a simple annual round determined by the calendar, seasonality in human societies is a complex system of interdependence between humans and non-humans. It requires close attentiveness to the variability of soils, weather, topography, plants, and animals across both time and space. In this article, the author investigates mobile systems of interdependence that take advantage of topographical and seasonal variation. He uses a range of case studies from early modern Scotland and Cyprus, focusing on summer grazing in the uplands and lowland agriculture carried out by mountain communities. After a comparative discussion of seasonality, the article examines the role of topography and movement, and then puts the ‘margins at the centre’ in order to highlight the central role played by seasonal activity and movement in rural society.

Rough-toothed dolphins (Steno bredanensis) are regularly present in continental shelf areas of the South-western Atlantic. However, there is little information on the natural history and ecology of these delphinids. This study evaluated the occurrence, habitat use and individual movements of the species in coastal waters off Rio de Janeiro, south-eastern Brazil. Data were obtained from boat surveys between August 2011 and May 2018, during which rough-toothed dolphins were sighted in 21 distinct events, predominantly in autumn and winter. The mean group size was 29 individuals. Rough-toothed dolphins were usually recorded 130 to 2300 m from the coast, between 7.6 and 28 m depths. In total, 115 individuals were catalogued through dorsal fin marks and 61 (53%) were resighted between one (47.5%) and four (9.8%) occasions. The interval between resightings ranged from seven to 2087 days (mean = 268). Agglomerative hierarchical clustering indicated 30 individuals (49.2%) in low degree, 12 (19.7%) in medium degree and 19 (31.1%) in high degree of site fidelity. Dolphins showed a higher frequency of low degree of habitat use, despite the presence of multiyear recaptures, which may be related to the prevalence of dolphin occurrence in autumn and winter, a large home range and/or the abundance and distribution of food resources. Dedicated surveys and regional collaboration are needed to evaluate the home range and population status of this species for their effective conservation. Our findings enhanced knowledge of this little studied species facing increasing anthropogenic threats in coastal waters off Rio de Janeiro.

Infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are often preceded by asymptomatic carriage. Higher incidences in enteric infectious diseases during summer have been reported. Here, we assessed whether the presence of seasonality in intestinal ESBL-Escherichia coli/Klebsiella pneumoniae (ESBL-E/K) carriage in the general Dutch population exists. From 2014 to 2017, the faecal carriage of ESBL-E/K in healthy individuals was determined in three cross-sectional studies in the Netherlands, including 5985 subjects. Results were pooled to identify seasonal trends in prevalence (by month of sampling). Multivariate logistic regression analysis was used to calculate pooled odds ratios and 95% confidence intervals. Results were adjusted for age, sex, antibiotic use and travel. Overall prevalence of ESBL-E/K carriage was 4.3% (n = 260 ESBL-E/K-positive), with differences between months ranging from 2.6% to 7.4%. Compared to January, the monthly prevalence of ESBL-E carriage was highest in August (OR 1.88, 95% CI 1.02–3.49) and September (OR 2.25, 95% CI 1.30–3.89). The observed monthly differences in ESBL-E/K carriage rates suggest that there is seasonal variation in exposure to ESBL-E/K other than due to travelling and antibiotic use. This should be taken into account in designing future ESBL-E prevalence studies in temperate regions.

We present a time series of 13 years (2003–2016) of continuous monthly data on the prevalence and mean abundance of the trematode Oligogonotylus mayae for all the hosts involved in its life cycle. We aimed to determine whether annual (or longer than annual) environmental fluctuations affect these infection parameters of O. mayae in its intermediate snail host Pyrgophorus coronatus, and its second and definitive fish host Mayaheros urophthalmus from the Celestun tropical coastal lagoon, Yucatan, Mexico. Fourier time series analysis was used to identify infection peaks over time, and cross-correlation among environmental forcings and infection parameters. Our results suggest that the transmission of O. mayae in all its hosts was influenced by the annual patterns of temperature, salinity and rainfall. However, there was a biannual accumulation of metacercarial stages of O. mayae in M. urophthalmus, apparently associated with the temporal range of the El Niño-Southern Oscillation (five years) and the recovery of the trematode population after a devasting hurricane. Taking O. mayae as an example of what could be happening to other trematodes, it is becoming clear that environmental forcings acting at long-term temporal scales affect the population dynamics of these parasites.