Background: The burden of COVID-19 was extremely severe in Northern Italy, an area characterized by high concentrations of particulate matter (PM), which is known to negatively affect human health. Consistently with evidence already available for other viruses, we initially hypothesized the possibility of SARS-CoV-2 presence on PM, and we performed a first experiment specifically aimed at confirming or excluding this research hyphotesys. Methods: We have collected 34 PM10 samples in Bergamo area (the epicenter of the Italian COVID-19 epidemic) by using two air samplers over a continuous 3-weeks period. Filters were properly stored and underwent RNA extraction and amplification according to WHO protocols in two parallel blind analyses performed by two different authorized laboratories. Up to three highly specific molecular marker genes (E, N, and RdRP) were used to test the presence of SARS-CoV-2 RNA on particulate matter. Results: The first test showed positive results for gene E in 15 out of 16 samples, simultaneously displaying positivity also for RdRP gene in 4 samples. The second blind test got 5 additional positive results for at least one of the three marker genes. Overall, we tested 34 RNA extractions for the E, N and RdRP genes, reporting 20 positive results for at least one of the three marker genes, with positivity separately confirmed for all the three markers. Control tests to exclude false positivities were successfully accomplished. Conclusion: This is the first evidence that SARS-CoV-2 RNA can be present on PM, thus suggesting a possible use as indicator of epidemic recurrence.

The study of any intervention able to counteract SARS‐CoV‐2 pandemic is considerably envisaged. It was previously shown, in in vitro models of infections, that the LED blue light is able to decrease the viral load of HSV‐1 and ZIKV. In our study, LED photobiomodulation therapy (PBMT) at blue wavelengths (450, 454 and 470 nm) was tested in an in vitro model of SARS‐CoV‐2 infection, employing three experimental settings: SARS‐CoV‐2 was irradiated and then transferred to cells; already infected cells were irradiated; cells were irradiated prior to infection. A decrement of the viral load was observed when previously infected cells were irradiated with all three tested wavelengths and relevant effects were registered especially at 48 hours post‐infection, possibly suggesting that the blue light could interfere with the intracellular viral replication machinery. Our in vitro findings could represent the starting point for translational applications of PBMT as a supportive approach to fight SARS‐CoV‐2.

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Chlamydia trachomatis and HPV coinfections in the male population are often a disregarded issue. We performed a study to evaluate the prevalence of such infections in heterosexual HIV negative men from a Northern Italy multi-ethnic area at high prevalence for cervical malignancies. Urethral swabs (US) or first-voided urine were evaluated retrospectively from 1317 patients attending Sexually Transmitted Infections (STI) clinic and from 3388 outpatients attending private clinics. Informations about participants' demographic characteristics and attributes of C. trachomatis, including chronic infection, and HPV genotypes testing, were collected. Exact Fisher test, bivariate, and multivariate logistic regressions were carried out. The prevalence of C. trachomatis was 1.7% in the outpatients and 16.9% in the STI group (P < 0.0001) in which the highest frequency was observed in men of age ≤25 years. Among patients with C. trachomatis, asymptomatic HPV co-infection was detected in 33% of men from the STI clinic and in 2% of the outpatients. Out of all coinfections, 56% were due to single HPV, with a prevalence of 73% in young STI men. The distribution of HPV genotypes confirmed the increased circulation of LR-HPV42, HR-HPV51, HR-HPV52 and prHR-HPV82, and the decreasing of HR-HPV16. African nationalities and leucorrhea were significantly associated risk factors, while the regular condom use offered an effective protection. This study highlights the high prevalence of C. trachomatis and HPV asymptomatic co-infection in young HIV negative men attending the STI clinic, representing a reservoir of new HPV genotypes with potential oncogenic risk.

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is mainly transmitted through respiratory droplets from positive subjects to susceptible hosts or by direct contact with an infected individual. Our study focuses on the in vitro minimal time of viral absorption as well as the minimal quantity of virus able to establish a persistent infection in Vero E6 cells. We observed that 1 min of in vitro virus exposure is sufficient to generate a cytopathic effect in cells after 7 days of infection, even at a multiplicity of infection (MOI) value of 0.01. Being aware that our findings have been obtained using an in vitro cellular model, we demonstrated that short-time exposures and low viral concentrations are able to cause infection, thus opening questions about the risk of SARS-CoV-2 transmissibility even following short contact times.

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is mainly transmitted through respiratory droplets, aerosols, or direct contact with fomites from an infected subject. It has been reported that SARS-CoV-2 is stable and viable in aerosol up to 16 h in controlled laboratory conditions. However, the aerosolization conditions varied a lot between the studies. In this work, an experimental laboratory model of SARS-CoV-2 aerosolization was established, employing an impinger nebulizer, a cylindrical chamber for aerosol travel, and a SKC biosampler for the collection of particles. The efficiency of the system was assessed based on the molecular determination of the viral load in the nebulizer after the aerosolization and in the aerosol collected at the end of the travel. Moreover, the residual infectivity was tested in vitro on the Vero E6 cell line, through the observation of the cytopathic effect (CPE), and the quantification of the viral load in the supernatants at 7 days post inoculation (dpi). A high RNA viral load was found in the SKC biosampler after aerosolization, indicating that it was possible to transport a high virus titer through the 30-cm chamber with all the dilutions (initial 105, 104, 103 plaque forming unit—PFU/mL). At the 7 dpi, an increment of the RNA viral load was determined for the dilutions 105 and 104 PFU/mL tested, while only the initial 105 PFU/mL resulted in visible CPE. Our findings allowed us to achieve the resilience of SARS-CoV-2 in aerosol form, at a concentration comparable to those reported for clinical samples. This mode of transmission should be considered for the mitigation and preventive measures to counteract SARS-CoV-2 spreading.

Blue light has been already reported as able to counteract different types of microorganisms including Gram‐positive and Gram‐negative bacteria, fungi and viruses, especially the enveloped ones. It has been reported that both blue and visible light can efficiently impact SARS‐CoV‐2 by affecting its ability to replicate in in vitro cellular models of infection. In this study, blue light at 450, 454 and 470 nm was tested on SARS‐CoV‐2 to evaluate the residual viral infectious potential on Vero E6, Caco‐2 and Calu‐3 cells, after the irradiation of viral particles. Following 12' of irradiation at 40 mW/cm2, a drastic block of viral amplification was observed. Indeed, at 7 days post‐irradiation/infection the viral load was the same as the one measured 1 day post‐irradiation/infection, and cellular viability was maintained showing similar levels to the noninfected control cells. Taken together our results indicate that blue LED lamps can be considered as a cheap and convenient tool for SARS‐CoV‐2 disinfection.

Coronavirus disease 19 (COVID-19) clinical manifestations include the involvement of the gastrointestinal tract, affecting around 10% of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected children. In the present work, the consequence of a short time of viral absorption (5, 15, 30 and 60 min) was tested on the Caco-2 intestinal epithelial cell line. Our findings show that Caco-2 cells are highly permissive to SARS-CoV-2 infection, even after 5 min of viral inoculation at a multiplicity of infection of 0.1. No cytopathic effect was evident during the subsequent 7 days of monitoring; nevertheless, the immunofluorescence staining for the viral nucleocapsid confirmed the presence of intracellular SARS-CoV-2. Our findings highlight the very short time during which SARS-CoV-2 is able to infect these cells in vitro.