Firstly, it is important to be clear about terminology used, as there has been confusion in the media over this. Contamination, as you’ll no doubt know, is used to describe material (e.g. organic soil, infectious particles) stuck to objects, including people, making it dirty.
Infection describes the invasion of infectious organisms or proteins into a body space and causing an inflammatory response. Clothes and surfaces get contaminated, people get infected. Forearms, in the absence of a rip-roaring cellulitis, are contaminated rather than infected.
SARS-CoV-2 is spread by respiratory droplets and survives a decent amount of time in the environment. The exception is when we intervene and make the droplets smaller, generally by doing something that generates high pressure within the airways (e.g. pressurised oxygen flows, poking plastic down their throat).
The only difference here is the diameter of the particle - droplets are large and fall to the floor, aerosols are small and stay in the air for a variable length of time. As a result, droplets are likely to be within a 1m radius of the source, whereas aerosolised particles can spread well over the 1m radius. To cause infection in a new host the virions have to get from their current host to their new host’s mucosal membranes via these particles. The ones that most of us have routinely on display are within the nose, the mouth and the surface of the eyes. The others are normally covered by clothing, unless a person is literally “bare below the elbows”.
Fluid repellent disposable gowns are those used for aerosol generating procedures (AGPs) or in operating theatres. The fabric gowns do not protect the wearers' clothes completely, as large droplets, or repeated inoculations of small particles, will soak through the material. This does not happen with plastic aprons
Protecting yourself from coughs and sneezes
Under normal conditions, assume the air around a COVID-19 patient is filled with a very small number of aerosol particles and lots of droplets intermittently (coughing and sneezing produce very little in the way of aerosol but lots and lots of droplets - COVID is mainly a dry cough and rarely any sneezing). The high risk areas for that member of staff to cover are the nose and mouth and, if you are going to be face-to- face with someone who doesn’t cover their mouth when they cough or sneeze, then your eyes need protection (hence the risk assessment).
Most people do not face their patients directly, they sit at 90 degrees instead so they are out of the direct blast zone for respiratory secretions. Appropriately worn PPE and hand hygiene will prevent direct inoculation.
The next highest risk, although much more common in practice, is indirect contact through lifting the virus particles from surfaces (mainly upward-facing ones) on hands. This is why we wear gloves and decontaminate our hands using the seven step technique (which includes washing the forearms for those bare below the elbows conventionally) after each of the WHO-endorsed five moments for hand hygiene.
Walking through the room in your clothes and stuff settling on your forearms is a minimal risk, particularly if you follow the guidance recommending that you change your clothes and launder them after each shift (scrubs, normal clothes, a toga, doesn’t matter so long as you wash them) and have a wash or shower.
Unless you go around licking your forearms before performing appropriate hand hygiene the risk is minimal. If someone sneezes on your forearm then the risk is higher, but I would then expect that person to wash immediately after such an event.
Hand hygiene remains the most important protective measure
For as long as I can remember doctors questioned the evidence around hand hygiene advice (particularly bare below the elbows). Any that had the misfortune to mention it to me got a collection of papers ranging from Cochrane reviews, works by Prof Didier Pittet and a lovely recent paper published by Semmelweis et al (1895) emailed to them, showing that hand hygiene is the single most important protective measure we can take.
The mask, gloves and hand hygiene are the most important aspects and probably cover 95% of it. The visor covers another approx. 4%. What you’re wearing really accounts for precious little of this, especially when combined with the fact that you are going to be washing the rest of it in the shower or washing machine instead of preening yourself with your tongue like a cat.
About Dr David Farren
Dr Farren MB BCh BAO MSc MRCP (2007) FRCPath, is a consultant medical microbiologist and infection control doctor working for Northern Health and Social Care Trust in Northern Ireland.
He is also chair of the NHSCT LNC; chair of the BMA Northern Ireland Regional LNC Forum; deputy chair of the Northern Ireland Consultants' Committee and representative of UKCC and NIC.