"The extremely fast transmission capability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has aroused concern about its various transmission routes,” according to a report published by the Centers for Disease Control and Prevention (CDC). SARS-Co-V-2 is thought to be transmitted through two main routes: breathing in the virus or coming into close contact with respiratory droplets from an infected person. Understanding the contamination conditions of the virus in hospital wards is “critical for improving safety practices for medical staff.”
Previous studies have detected the virus on object surfaces in a symptomatic patient’s room and toilet area, as well as on surgical masks for up to a week and on plastic for up to 72 hours. But whether the novel coronavirus can be transmitted through aerosols is still controversial, notes the CDC.
In order to determine how far SARS-CoV-2 can spread, researchers tested air and surface samples in an intensive care unit (ICU) and a general COVID-19 ward at Huoshenshan Hospital in Wuhan, China, between February 19 and March 2. The ICU contained 15 patients with severe disease and the general ward had 24 patients with milder disease. Collected swab samples were taken from objects that may have been contaminated, as well as from indoor air and air outlets.
Viral contamination was found to be greater in the ICU (43.5 percent) than in general wards (less than 8 percent). Floor samples also tested positive for the virus, which could be because gravity causes most virus droplets to sink to the ground or medical staff are accidentally tracking the virus around with their shoes – a possibility that is evidenced by a 100 percent positive rate for samples taken from the pharmacy where no patients were present. Additionally, nearly half of the samples from ICU medical staff shoe soles tested positive, suggesting that shoes could serve as carriers.
A high presence of the virus was also found on items that were frequently touched by medical staff or patients, including computer mice, trash cans, sickbed handrails, and doorknobs.
The authors point out several limitations to the study. First, sample testing found the presence of the virus but did not determine whether it was viable and could be contracted. Second, it is not clear what amount of the virus must be present in aerosol form to be considered an “infectious dose”.
Even so, the findings can be used to improve safety practices in a variety of settings, including hospitals. The CDC highly recommends people disinfect their shoe soles before walking out of wards containing COVID-19 patients and adds that stricter safety measures should be applied to medical staff and those working in close contact with patients in the ICU. Masks were also shown to have a high presence of the virus, which means that users should sanitize them before discarding.
The study is not in final print and may be updated between now and when the finalized version is released in July.