The role of air temperature in Legionella water contamination and legionellosis incidence rates in southern Italy (2018-2023)

Background

Legionnaires' disease is caused by inhalation or aspiration of small water droplets contaminated with Legionella, commonly found in natural and man-made water systems and in moist soil. Over the past 5 years, notification rates of this disease have almost doubled in the European Union (EU) / European Environmental Agency (EEA), from 1.4 in 2015 to 2.2 cases per 100,000 population in 2019. Some studies show that the greater presence of the microorganism in the water network and the increase in cases of legionellosis could be related to the variations in some environmental factors, such as air temperature, which may influence the water temperature.

Study design

Climate change is currently a prominent topic worldwide because of its significant impact on the natural environment. It is responsible for the increase in numerous waterborne pathologies. The purpose of this study was to correlate the air temperature recorded in Apulia region from January 2018 to April 2023 with the presence of Legionella in the water networks of public and private facilities and the incidence rates of legionellosis during the same period.

Methods

During the period from January 2018 to April 2023, water samples were collected from facilities involved in legionellosis cases and analyzed for Legionella. During the same period, all the cases notified to the regional epidemiological observatory (OER-Apulia) were included in this study. Statistical analyses were conducted using the Shapiro-Wilk test to determine whether the Legionella load was distributed normally, the Wilcoxon rank sum test to compare the air temperatures (average and range) of the negative and positive samples for Legionella detection, and the multivariate analysis (Poisson regression) to compare the Legionella load with the water sample temperature, average air temperature, and temperature range on the day of sampling. The Wilcoxon test for paired samples was used to compare legionellosis cases between the warmer and colder months.

Results

Overall, 13,044 water samples were analyzed for Legionella and 460 cases of legionellosis were notified. Legionella was isolated in 20.1% of the samples examined. The difference in the air temperature between negative samples and positive samples was statistically significant (p-value < 0.0001): on days when water samples tested positive for Legionella a higher temperature range was observed than on days when water samples tested negative (p-value = 0.004). Poisson regression showed a direct correlation between Legionella load, water temperature, and average air temperature. The incidence of legionellosis cases in warmer months was higher than in colder months (p-value = 0.03).

Conclusions

Our study highlights a significant increase in the load of Legionella in the Apulian water network, and an association between warmer temperatures and legionellosis incidence. In our opinion, further investigations are needed in different contexts and territories to characterize the epidemiology of legionellosis, and to explain its extreme variability in different geographical areas and how these data may be influenced by different risk factors.

Classwork and homework in early adolescence: The ecology of achievement

Recent studies have questioned whether the nation's educational system is adequately preparing children to function productively in today's society. To examine this issue, the present study utilized the Experience Sampling Method to investigate the amount of time young adolescents spent doing classwork and homework, their inner subjective experience while doing so, and their companions while doing homework. The relationship between these variables and students' academic performance was also examined. Results revealed that students spent only 15.5 hours per week engaged in school work and only 6 hours per week doing homework, with increased homework time associated with better academic achievement. In addition, students were found to complete homework primarily alone or in classes, although doing homework with their parents was associated with better academic performance. Lastly, students' affect was found to be relatively neutral when doing classwork, but comparatively more negative while doing homework, particularly when doing homework alone. The implications of these findings for understanding the socializing influence of school are discussed.

Role of 5-hydroxytryptamine in amphetamine effects on punished and unpunished behaviour

In order to assess the contribution of serotonergic (5-HT) mechanisms in the suppressant effect of amphetamine on punished responding, dose-effect curves of amphetamine on key-pecking behaviour of pigeons maintained by food presentation and punished by electric-shock were determined before and after pretreatment with methergoline, a potent and specific 5-HT receptor blocker in the central nervous system. A multiple fixed-interval 5 min, fixed-interval 5 min schedule of reinforcement in which every response, except the reinforced one, was punished in one of the two components (mult FI5 FI5-shock) was used. Effective doses of amphetamine decreased unpunished as well as punished FI response rates. However, the decreases in punished behaviour were more evident and dose-dependent. Methergoline markedly increased FI responding in the punished FI component but only slightly increased or decreased unpunished FI response rates. The most effective dose of methergoline for increasing punished responding was 0.56 mg/kg. Pretreatment with this dose of methergoline unmasked the facilitatory effects of amphetamine on unpunished responding, but did not antagonize its suppressant effect on punished responding. Therefore, although 5-HT seems to mediate punishment-induced response suppression and to inhibit the facilitatory effects of amphetamine on unpunished responding, it is not apparently involved in the suppressant effect of amphetamine on punished behaviour.

Effect of amphetamine on nondiscriminated key-pecking avoidance in pigeons

Dose-effect curves for amphetamine on key-pecking behavior of pigeons maintained by two-component multiple schedules of shock postponement were determined. During the first experimental phase the response-shock interval (RS) was held constant and the shock-shock interval (SS) varied. Under these conditions, shock rate was greater during the component with the shorter SS. However, response rates were comparable in both components. Also, the magnitude of the response rate increments caused by appropriate doses of amphetamine during both schedule components were similar. During the second experimental phase, the SS was held constant and the RS varied. As a consequence, baseline response rate was considerably lower in the component with the longer RS than in the short RS component. Shock presentations were also less frequent during the former than during the latter component, but the differences in shock rate between the components were comparable or smaller than those observed during the first experimental phase. Under these conditions, the effects of amphetamine in the two schedules components were markedly different, lower response rates being considerably more increased than higher rates.