NEW YORK (Reuters) –
Of the 347 individual samples collected from the rooms of 20 patients infected with SARS-CoV-2, less than 6% were positive via RT-PCR, and only one demonstrated cytopathic effect (CPE), researchersin Clinical Infectious Diseases.
“The presence of SARS-CoV-2 genetic material on health care surfaces is not necessarily an indicator of live infectious virus,” said lead author Dr. Bobby Warren, lab director of the DiRTE (Disinfection, Resistance, and Transmission Epidemiology) lab in the Duke Center for Antimicrobial Stewardship and Infection Prevention (DCASIP), Durham, N.C.
“The amount of environmental contamination that is considered an infectious dose of SARS-CoV-2 has not been established,” Dr. Warren told Reuters Health by email. “Although, samples only contaminated with genetic material are unlikely to cause illness.”
The findings might not apply everywhere, Dr. Warren said.
“This study is only generalizable to the specific setting it was completed in (an acute health care setting in patient rooms located on a dedicated COVID-19 inpatient unit), not other health care, community, or personal settings,” Dr. Warren said. “On this dedicated COVID-19 unit, PPE, routine disinfection, and special airborne precautions were taken by all staff, likely reducing the amount of SARS-CoV-2 surface contamination.”
To explore the question of how often surfaces in COVID-19 patients’ hospital rooms become contaminated with the SARS-CoV-2 virus, Dr. Warren and his colleagues conducted a prospective study of inpatient rooms occupied by COVID-19 patients between October 2020 and June 2021.
The single-occupancy rooms included in the study housed COVID-19–positive patients who had a first positive test within 24 hours of enrollment. The researchers note that a previous study found that the air in these rooms was exchanged about 14 times every hour.
The researchers collected environmental samples on study day one and again on days three, six, 10 and 14. The sample swabs were vortexed 10 seconds to remove viral particles. Then the swabs were discarded and RNA extractions completed. Samples that were positive for the virus via RT-PCR were inoculated into Vero E6 cells in two passages, and the cells were monitored for CPE every 48 hours.
The 21 patients enrolled in the study spent a median of six days in the hospital and five in the study room, and 16 (80%) of the study rooms had been previously occupied by a COVID-19 patient. Three-quarters of the patients were actively symptomatic.
Overall, 19 (5.5%) of the samples were positive via RT-PCR: nine from bedrails, four from sinks, four from room computers, one from the medical prep area, and one from the exit door handle. Nursing station computer samples were negative.
Of the positive samples, six were from day one, 10 from day three, two from day six and one from day 10. All the positive samples were screened for infectious virus via cell culture, with just one, which had been obtained on day three from the bedrails of a symptomatic patient with diarrhea and fever, demonstrating CPE, and the harvested inoculates were SARS-CoV-2 RT-PCR positive, which indicated viral growth.
Reuters Health Information © 2022