Sampling Methods and Risk Stratification Regarding Environmental Contamination by SARS-CoV-2

Area of Science:

• Infectious Diseases
• Environmental Microbiology
• Public Health

Background:

• COVID-19 transmission via droplets is known, but aerosol and surface contamination require further investigation.
• Limited and inconsistent literature exists on viable virus particle distance and surface swabbing methods.
• Understanding environmental contamination is crucial for infection control strategies.

Purpose of the Study:

• To identify the most sensitive method for assessing surface contamination.
• To categorize environmental contamination risk zones based on proximity to patients.
• To compare surface contamination levels between different oxygenation and ventilation support methods.

Main Methods:

• Collected swabs from surfaces in a COVID-19 ward with patients receiving various respiratory supports.
• Compared three different swab types to determine the most sensitive collection method.
• Defined risk zones based on distance from the infected patient.

Main Results:

• 17 out of 63 (27%) swabs tested positive for SARS-CoV-2.
• The highest positivity rate (48%) was found in high-risk zones, one meter from the patient.
• Rooms of patients on non-invasive ventilation (45%) and high-flow nasal cannula (27%) showed significant bedroom contamination.

Conclusions:

• Sterile premoistened swabs without transport medium are favored for surface contamination assessment.
• Risk zones should be classified based on patient distance, with higher risk closer to the patient.
• Ventilatory support strategies significantly influence surface contamination, likely due to increased particle dispersion.