WATER HYGIENE AND SAFETY


Reducing the aspiration risks of waterborne pathogens


Jonathan Waggott, an expert in sanitary infection control issues who runs his own consultancy, discusses the risks posed by airborne transmission of a variety of harmful pathogens from outlets such as taps, sinks, and showers, in hospitals and other healthcare premises, and some of the actions that can be taken to help mitigate these risks.


During the past 5-10 years healthcare- acquired infections have been the subject of very high levels of public, media, and government attention. Unacceptable levels of sickness and death have become associated with poor hand hygiene and inadequate cleaning. In many countries, initiatives addressing education, cleaning, and audit, together with compulsory reporting of infections, have brought about benefits, leading (in some cases) to the reduction of headline rates of infections, such as methicillin- resistant Staphylococcus aureus (MRSA), Clostridium difficile, and Legionnaires’ Disease. It is readily accepted now that a common mode of transmission is contact between the patient, the staff, and the environment. A number of studies have shown that outbreaks can be reduced via improved hand hygiene compliance and better cleaning of the environment. However, transmission of infection via the air has often been less well investigated, sometimes leading to complacency over this mode of transmission.


Airborne transmission It is clearly understood now that tuberculosis (TB; Mycobacterium tuberculosis) is transmitted through the air, and can be a source of outbreak in hospitals. Healthcare workers infected with TB can spread the infection widely. Similarly, norovirus can be transmitted by aerosol, and is difficult to contain in a hospital ward without sufficient single rooms with en-suite toilets. Historically, natural ventilation was seen to be beneficial in hospital wards, and was part of hospital design. With the advent of sealed, high-rise buildings and forced


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transport over long distances, and contaminate surfaces by falling down.


Penetration into the lungs It has been proven that droplets can contaminate surfaces in a range of over two metres.2


The droplets are capable


of penetrating deep into the lungs, offering a potential route of infection.3 An individual’s susceptibility to acquiring an infectious agent is determined by factors such as virulence, dose, and pathogenicity of the microorganism, and the host’s immune response.3–5 Humans generate bio-aerosols by talking, breathing, sneezing, or coughing.1


Based


on the infectious status of a person, the bio-aerosols can contain pathogens including influenza,6,7 tuberculosis,3


Mycobacterium Staphylococcus aureus,


Varicella-Zoster Virus, Streptococcus spp., or Aspergillus spp.8


Moreover, bio- Water from a tap produces aerosol.


ventilation, expensive negative pressure rooms have sometimes been introduced to house patients with infections thought likely to be transmitted by aerosol. Aerosols can be defined as liquid or solid particles suspended in the air by humans, animals, instruments, or machines. 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 airborne microorganisms by air, consist of small particles named droplet nuclei (1–5 μm), or droplets (>5 μm). Droplet nuclei can stay airborne for hours,


With the advent of sealed, high-rise buildings and forced ventilation, expensive negative pressure rooms have sometimes been introduced to house patients with infections thought likely to be transmitted by aerosol


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.4,5,9 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 Legionella pneumophila serogroup 6 was present in 9 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 2 to 10 days before the onset of disease symptoms. They also isolated the bacteria in two other hospitals, and found that 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


February 2019 Health Estate Journal 39


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