SARS-CoV-2 Surface Contamination and Viable Virus in High-Ventilation Single Rooms: Implications for Fomite...

To evaluate Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) contamination in the rooms of Coronavirus disease 2019 (COVID-19) patients by integrating RNA quantification, viral culture, and post-culture cycle threshold (Ct)-based estimation of infectious titer, and to reassess fomite transmission risk relative to the human infectious dose.

In nine high-ventilation, single-occupancy rooms, adhesive 36 cm² samplers (stickers for hard surfaces; cloth patches for textiles) were placed on 14 environmental surfaces and on the upper back of night-shift nurses' scrubs for the first 24 hours after admission. N-gene copies were quantified by quantitative reverse transcription PCR (qRT-PCR); infectivity was assessed on VeroE6/TMPRSS2 cells. For culture-positive samples, culture-supernatant Ct values were converted to estimated infectious titers using a published regression. Distance, material, and Severity classification factors were analyzed in prespecified univariable models.

Of 134 specimens, 66 (49.3%) were RNA-positive, with a maximum of 8.48 log₁₀ copies per sample, highest values on high-touch surfaces close to patients. Infectious virus was isolated from 4/134 specimens (3.0%). Estimated infectious titers were approximately 5.7 × 10²-2.6 × 10³ TCID₅₀-eq per sample. Both RNA positivity and viral RNA copy numbers declined significantly with increasing distance from the patient's mouth.

In high-ventilation rooms, environmental surface contamination was common and viable virus was occasionally present near patients. Estimated titers on some high-touch surfaces exceeded the reported human infectious dose, implying that fomite transmission may remain plausible under specific conditions. Prioritized cleaning/disinfection of high-touch surfaces near patients, along with consistent hand hygiene, are warranted, alongside ventilation/filtration measures.