Relative contributions of transmission routes for COVID-19 among healthcare personnel providing patient care

• Published in: Journal of occupational and environmental hygiene Vol. 17; no. 9; pp. 408 - 415
• Main Author: Jones, Rachael M.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 01.09.2020; Taylor & Francis LLC
• Subjects: Air sampling; Animals; Betacoronavirus; Coronavirus Infections - epidemiology; Coronavirus Infections - transmission; Coronaviruses; COVID-19; Disease transmission; Droplets; Emission; Emissions; exposure modeling; Health care; Health Personnel; Humans; Infection Control - instrumentation; Infections; Infectious Disease Transmission, Patient-to-Professional - prevention & control; Infectivity; Inhalation; Markov Chains; Medical personnel; Mice; Microorganisms; Models, Theoretical; Pandemics; Personal protective equipment; Personal Protective Equipment - statistics & numerical data; Personnel; Pneumonia, Viral - epidemiology; Pneumonia, Viral - transmission; Protective equipment; quantitative microbial risk assessment; Respiration; Respiratory protection; Respiratory Protective Devices - statistics & numerical data; Risk assessment; Sampling methods; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2; viral aerosol; Viral diseases; Viruses; exposure modeling; Respiratory protection; personal protective equipment; viral aerosol; quantitative microbial risk assessment
• ISSN: 1545-9624; 1545-9632; 1545-9632
• DOI: 10.1080/15459624.2020.1784427

The routes of COVID-19 transmission to healthcare personnel from infected patients is the subject of debate, but is critical to the selection of personal protective equipment. The objective of this paper was to explore the contributions of three transmission routes-contact, droplet, and inhalation-to the risk of occupationally acquired COVID-19 infection among healthcare personnel (HCP). The method was quantitative microbial risk assessment, and an exposure model, where possible model parameters were based on data specific to the SARS-CoV-2 virus when available. The key finding was that droplet and inhalation transmission routes predominate over the contact route, contributing 35%, 57%, and 8.2% of the probability of infection, on average, without use of personal protective equipment. On average, 80% of inhalation exposure occurs when HCP are near patients. The relative contribution of droplet and inhalation depends upon the emission of SARS-CoV-2 in respirable particles (<10 µm) through exhaled breath, and inhalation becomes predominant, on average, when emission exceeds five gene copies per min. The predicted concentration of SARS-CoV-2 in the air of the patient room is low (< 1 gene copy per m 3 on average), and likely below the limit of quantification for many air sampling methods. The findings demonstrate the value of respiratory protection for HCP, and that field sampling may not be sensitive enough to verify the contribution of SARS-CoV-2 inhalation to the risk of occupationally acquired COVID-19 infection among healthcare personnel. The emission and infectivity of SARS-CoV-2 in respiratory droplets of different sizes is a critical knowledge gap for understanding and controlling COVID-19 transmission.