Contaminazione da SARS-CoV-2 delle superfici delle ambulanze ed efficacia della procedura di sanificazione di routine: una classica lezione di igiene per un nuovo patogeno.

Background Shortly after the onset of the COVID-19 pandemic, efficacy of routine ambulance sanification (i.e. sodium hypochlorite 0.1% and 20-minute ozone saturation of cabin) against SARS-CoV-2 was debated. Commonly, a differential use of ambulances was promoted, with a number of vehicles exclusively transporting COVID-19 confirmed/suspected cases. The present study investigated the presence of SARS-CoV-2 on selected surfaces of COVID-19 ambulances to detect possible contamination dynamics and evaluate the effectiveness of the sanification procedure. Methods Two Emergency Medical Services (EMS) teams attended a training on WHO surface sampling methods for SARS-CoV-2. Four high-touch surfaces were sampled for each transport event, before and after sanification (T0, T1): sliding door handle; touch-screen monitor; oxygen-flow knob; stretcher handles. Gloves of the leading EMS nurse were also sampled, although uniquely at T0. Sigma Virocult® swabs were used for surface sampling. Swabs were kept at 4°C and processed within 48hrs from collection. RNA extraction was performed with the QIAamp viral RNA mini kit (Qiagen). Molecular detection of SARS-CoV-2 RNA was performed with a RT qPCR assay, targeting the N gene. Positivity was qualitatively attributed to reactions with cycle threshold (Ct) <40. Transported patients were also tested for SARS-CoV-2 upon arrival at the hospital. Results Eleven transport services were sampled, with 9 confirmed COVID-19 cases. One patient resulted negative; 1 swab result could not be retrieved. Seven transports had at least 1 positive sample: all were related to a confirmed COVID-19 case. Among the 4 negative transports, 3 dealt with a confirmed COVID-19 case and 1 with the negative patient. One door handle and 1 oxygen knob were positive at T0, with all of the respective T1 swabs being negative. The monitor was positive in 5 transports at T0, yet never at T1. Three stretcher-handles tested positive at T0 and 2 of them maintained positivity at T1, possibily bypassing sanification due to dismounting from the ambulance. Gloves resulted contaminated in 5 transports: among these, 1 to 3 additional samples (monitor, knob, stretcher) resulted positive. Conclusions The effectiveness of routine sanification for ambulances was confirmed, although highlighting the stretcher dismounting as a critical step, at least under the unprecedented burden conditions of the COVID-19 emergency. Rather than an upgrade of sanification procedures, the importance of correct hand-hygiene and glove-disposal should be emphasized through dedicated training of EMS personnel. Beside COVID-19, microbial contamination in ambulances should especially be addressed to prevent any healthcare-associated infection.