SARS-CoV-2 Not Found on PPE After Health Worker Contact With Infected Patients: Pilot Study

By Lisa Rapaport

March 27, 2020

(Reuters Health) - Healthcare workers treating patients infected with SARS-CoV-2 did not appear to have traces of the virus on their personal protective equipment (PPE) when they exited patient rooms, a pilot study in Singapore found.

To evaluate the safety of extended PPE use, researchers conducted a one-day PPE sampling study on doctors, nurses and cleaners caring for confirmed SARS-CoV-2 infected patients to ascertain the per-contact-episode risk of PPE contamination.

Samples were collected using a standardized technique with pre-moistened sterile swabs from the entire front of goggles, front surface of N95 respirator, and front surface of shoes from 30 healthcare workers exiting patient rooms. Gloves and gowns were not swabbed because they were discarded after each use, Sean Wei Xiang Ong, of the National Centre for Infectious Diseases and Tan Tock Seng Hospital in Singapore, and colleagues note in Infection Control & Hospital Epidemiology.

All 90 samples were negative for SARS-CoV-2, the pilot study found. The workers spent a median of 6 minutes in patient rooms (interquartile range 5-10 minutes). Activities ranged from casual contact, like administering medicine or cleaning, to closer contact, such as physical exams or collection of respiratory samples

"This provides assurance that extended use of N95 and goggles with strict adherence to environmental and hand hygiene while managing SARS-CoV-2 patients could be a safe option," the study team writes.

All of the patients in the study had a positive test for SARS-CoV-2 within the previous 48 hours. None required respiratory support, and no aerosol-generating procedures were carried out prior to or during sampling.

One limitation of the study is the use of surface swabs for sampling the surface of N95 masks, rather than processing masks in extraction buffers with detergents, which is a method that has been used for isolation of influenza from N95 respirators, the authors note.

Surface swabbing may be insufficient for detection of entrapped viral particles, the researchers write.

In addition, all patients were in airborne-infection isolation rooms with 12 air exchanges per hour, and results under these conditions may not be generalizable to other room configurations.

Researchers did not assess the concomitant level of viral contamination of the environment in this study to correlate with the level of PPE contamination.

Even so, local transmission of SARS-CoV-2 infection in Singapore has been reported, and as the pandemic spreads globally, increased utilization and shortages of PPE are expected, the authors note. While extended PPE use would mitigate utilization rates, its safety is unknown, and the pilot study offers some preliminary findings to inform additional research, they write.

At the National Centre for Infectious Diseases, recommendations for healthcare workers in contact with known or suspected patients are in concordance with the U.S. Centers for Disease Control and Prevention, which recommends gloves, gown, respiratory protection (e.g. disposable N95respirator), and eye protection (e.g. goggles or disposable face shield), without use of shoe covers.

A spokesperson for the National Centre for Infectious Diseases said the study authors were not immediately available to comment.

SOURCE: Infection Control & Hospital Epidemiology, online March 26, 2020.