## 3 Results  
SARS-CoV-2 RNA was detected on 41/686 (6%) students' desks (Table 1), while all the other surface types were negative. Figure 2 shows the daily distribution of positive samples, restricted to the period ranging from June to November 2022. SARS-CoV-2 RNA was detected during a written exam (43.9%), followed by lessons and a medicine test (17.1% each), a graduation session (14.6%), and a workshop (7.3%). In the positive samples, the mean Ct was 38.04, and the median Ct was 38.09 (range 35.79-39.29). The positive sample with the lowest Ct (35.79 Ct), examined by the WGS, yielded a genome sequence that passed Nextclade's quality control. In silico analysis of the data obtained with WGS data allowed us to assign this sample to lineage BA.5.1.30 (clade 22B). The genomic sequence has been deposited in the GISAID database and is available under Accession ID EPI_ISL_17716776. The sequencing data obtained from the other positive samples did not meet the quality requirements due to insufficient genomic coverage and a high number of missing nucleotides along the sequence. No cytopathic effect was observed in any of the positive samples subjected to the viral viability test. Table 2 shows the presence of SARS-CoV-2 RNA on student desks by type of material. \begin{table}
\begin{tabular}{c c c c} \hline
**Tested Surface (No.)** & **Positive** & **Negative** & **\%** \\  & **(No.)** & **(No.)** & **\%** \\ \hline Students’ desks (686) & 41 & 645 & 6 \\ \hline Handles (20) & 0 & 20 & 0 \\ \hline Handrail (11) & 0 & 11 & 0 \\ \hline Mouse (7) & 0 & 7 & 0 \\ \hline Keyboard (7) & 0 & 7 & 0 \\ \hline Teachers’ desks (6) & 0 & 6 & 0 \\ \hline Others (26) & 0 & 26 & 0 \\ \hline Total (763) & 41 & 722 & 5.4 \\ \hline \end{tabular}
\end{table} 
Table 1: Number of samples positive and negative for SARS-CoV-2 RNA by type of surface and rate of positivity. Figure 2: Temporal distribution (%) of positive swab specimens for SARS-CoV-2 RNA during academic events (May–December 2022). The application of the chi-square statistic with Yates correction or the Fisher exact test statistic to the sampling results by type of surface and material did not lead to statistically significant results in either case. Analyzing the results according to the degree of crowding of university staff (students, teachers, administrators, etc.) in the environments (Table 3), a higher level of contamination was found in the larger classrooms (>50 students) than in the smaller ones (less than 50 students) (7.1% vs. 1.5%--chi-square statistic with Yates correction is 7.3304, \(p\)-value = 0.006). Regarding the seasonal trend of SARS-CoV-2, higher contamination was found in the spring-summer period (May-September 2022) than in the autumn (October-December 2022), with a statistically significant difference (7.3% vs. 2.4%--chi-square test with Yates correction = 7.6003; \(p\)-value = 0.006). The mean atmospheric monthly temperatures in Apulia from May to December 2022 differed significantly between seasons (spring-summer 24.1 \({}^{\circ}\)C [19.3-22.3 \({}^{\circ}\)C] and autumn 14.1 \({}^{\circ}\)C [10.2-18.1 \({}^{\circ}\)C], Mann-Whitney U test \(p<\) 0.05). The Poisson regression model (Table 4) showed that there was an inverse proportional association between the percentage of SARS-CoV-2 positive swabs on the day of sampling and seasonality (e.g., the number of positive swabs decreases from spring-summer to autumn). Instead, a direct proportional association was found between the percentage of SARS-CoV-2 positive swabs on the day of sampling and the average number of COVID-19 cases among university students in the seven days following sampling. The regression analysis reported in Table 5 showed a directly proportional association between average COVID-19 cases among university students in the seven days postsampling (Figure 3) and % of positive swabs for SARS-CoV-2, as well as between average COVID-19 cases in the seven days after and before sampling.