INF ECTION P R EVENTION
Bio-aerosols are aerosols consisting of particles of any kind of organism.1, 2 The characteristics of bio-aerosols differ depending on environmental influences such as humidity, air flow, and temperature. Aerosols, which are responsible for the transmission of micro-organisms by air, consist of small particles (droplet nuclei; 1–5µm) or droplets (>5µm). Droplet nuclei can stay airborne for hours, transport over long distances and contaminate surfaces by falling down. In a review article from 2006,5 the authors found for SARS-CoV-1 that “particles of diameters 1–3 µm remained suspended almost indefinitely, 10 µm took 17 min, 20 µm took 4 min, and 100 µm took 10 seconds to fall to the floor”.5
This
article notes that aerosol transmission is a well-known and important exposure pathway for infectious agents such as influenza and other viruses including coronaviruses. As discussed in this article, SARS-CoV-1 viral RNA was found in air samples, and long- range aerosol transport was implicated as the cause of the spread of the disease in several studies.6
It has been proven that droplets can contaminate surfaces in a range of over 2 metres.7
of penetrating deep into the lungs, offering a potential route of infection.8
The droplets are also capable The
susceptibility of acquiring an infectious agent is determined by factors such as: virulence; dose; and pathogenicity of the micro-organism; and the host’s immune response. 8-10
It has been proven already that Norovirus can be transmitted by aerosol and is difficult to contain in a hospital ward without sufficient single rooms with en-suite toilets. Now with the additional battle against COVID-19, the transmission by aerosol now needs to be urgently considered and the risks substantially reduced.
including influenza,11, 12 Mycobacterium tuberculosis,8 Staphylococcus aureus,
Varicella Zoster Virus, Streptococcus spp. or Aspergillus spp.12
Moreover, bio-aerosols
can be generated by devices such as ventilation systems, showers, taps and toilets. Showers and tap water are also able to spread environmental microbes such as Legionella spp..9, 10, 14
It is now commonly accepted that
bio-aerosols containing harmful pathogens are very much a common and serious contributor to healthcare-acquired infections but are these connections new and what was known of such threats in the past? In 1981 Cordes et al found that
Humans generate bio-aerosols
by talking, breathing, sneezing or coughing.6 Based on the infectious status of a person, the bio-aerosols can contain pathogens
Legionella pneumophila serogroup 6 was present in nine of 16 shower heads in a Chicago hospital ward where three patients had contracted Legionnaires’ disease caused by serogroup 6 L. pneumophila. Each patient had showered there two to 10 days before the onset of disease
symptoms. They also isolated the bacteria in two other hospitals and found the same serogroups as had been causing Legionnaires’ disease in those hospitals: serogroup 1 in Pittsburgh and serogroups 1 and 4 in Los Angeles. However, showers from hospital wards where no patients had contracted Legionnaires’ disease also yielded L. pneumophila. The question of whether aerosols of shower water or other exposures to potable water containing L. pneumophila may cause nosocomial Legionnaires’ disease was not proven but they suggested that is definitely deserved further study.16 In 1985, Meenhorst et al conducted an investigation into an outbreak of nosocomial legionella pneumonia. It revealed that the potable water of the hospital was contaminated with a distinctive strain of Legionella pneumophila (designated the Le-l strain), which was by culture and serology linked with human illness. To examine the possible role of this water in
Water from a tap produces significant aerosol dispersal. 34 l
WWW.CLINICALSERVICESJOURNAL.COM SEPTEMBER 2020
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