Results of a single-center observational study showed that SARS-CoV-2 transmission via fomites was possible but unlikely to occur in real-life scenarios. These findings were published in the Journal of Infectious Diseases.

Adults (N=15) hospitalized with COVID-19 infection at a Hospital Bochum in Germany between November 2020 and April 2021 were enrolled in this study. At baseline, reverse-transcriptase polymerase chain reaction testing of nasopharyngeal and oropharyngeal swab specimens showed that all patients had a high SARS-CoV-2 viral load. None of the patients required ventilation support. Patients were instructed to forcefully cough twice on predefined surfaces containing 9 standardized steel carriers and to then excessively moisten the carriers with their saliva for 10 seconds. After 1, 5, 15, 30, 45, 90, 120, and 240 minutes, the steel-carriers were transported on ice for laboratory testing, and viral abundance and transmissibility were quantified.

Among patients included in the study, the mean age was 70.5 (range, 39-89) years, 33.3% were women, 66.7% had arterial hypertension, 46.7% had chronic obstructive pulmonary disease, and 53.3% were active smokers. Of note, none of the patients were vaccinated against COVID-19 infection.


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At baseline, 60% of the patients had mild COVID-19-related symptoms. During the follow-up period, worsening symptoms were observed in 10 patients and mortality occurred in 3. On hospital admission, patients with severe disease were more likely to have increased concentrations of lactate dehydrogenase (r, 0.53; P =.044), leukocytes (r, 0.69; P =.0056), and C-reactive protein (r, 0.54; P =.035).

Infectious virus, defined as 50% tissue culture infective dose (TCID50/mL), was recovered from the swab samples of 6 (46.2%) patients.

After patients moistened the steel carriers with their saliva, detectable viral RNA was observed in 46.2% of the carriers, and infectious virus was recovered from 38.5%. Among the carriers with infectious virus, viral titers ranged from 5.59´101 to 8.68´105 TCID50/mL.

For the steel carriers that were evaluated after 240 minutes, infectious virus was recovered from 3, emphasizing the environmental stability of the SARS-CoV-2 virus.

After patients forcefully coughed onto the steel carriers, analysis showed that only 5 carriers had detectable SARS-CoV-2 viral RNA. Of these 5 carriers, none contained infectious virus.

This study was limited by potential selection bias, and the possibility that repeat coughing may have resulted in more effective viral transmission.

According to the researchers, “[these] findings suggest that fomites contaminated with coughing are unlikely to be an important source of SARS-CoV-2 transmission.”

Reference

Meister TL, Dreismeier M, Blanco EV, et al. Low risk of SARS-CoV-2 transmission by fomites – a clinical observational study in highly infectious COVID-19 patients. J Infect Dis. 2022;jiac170. doi:10.1093/infdis/jiac170