WHAT'S NEW - Disinfecting Hands and Surfaces
Disinfecting Hands and Surfaces
There is a lot of advice out there concerning how to kill coronavirus and its quality and utility varies widely. This bulletin is intended to strip away some of the myths and offer some sensible, real-life, practical advice.
For the pedants out there you can’t really kill a virus, technically it’s not ‘alive’ but for our purposes we’ll stick to ‘killing’ it. And we mean outside the body, this isn’t medical advice.
The good news is that the virus isn’t too tough to kill. People often conflate how serious an infectious agent can be if you catch it with how difficult it is to kill outside the body. Coronaviruses are ‘enveloped’ viruses and these are the easiest to kill; they have a protective, fatty envelope and because it’s a fat the virus gets ripped apart by detergents and soaps quickly rendering it harmless.
Hand Hygiene - Washing
Because the virus is so susceptible to soap and water, hand washing (as opposed to hand rubs / gels / foams) is always the gold standard. Take your time, lather the soap up well and don’t forget the most commonly neglected areas: the tips of the fingers, palm of the hand, and the thumb. And always dry your hands properly; wet hands are far more efficient at spreading germs. It doesn’t need to be antibacterial soap either; plain soap is fine.
Disposable paper has long been the preferred option of infection control specialists (including ours) but there is conflicting advice about warm air dryers and COVID. Manufacturers insist there’s no proof of any risk but what we do know is the air will definitely not be warm enough for long enough to kill the virus - and previous research has shown dryers are quite good at blasting germs around. While there is no hard evidence of a hand dryer being involved in someone having caught COVID-19 an abundance of caution suggests switching to paper if possible.
Hand Hygiene – Gels and Foams
Hygienic hand rubs are not as good as soap and water but if hand washing is not an option you need to look for either 60%+ isopropanol (propan-2-ol), 70%+ ethanol in a formulation. Non- alcohol rubs / foams are available too; it’s a myth that ‘only alcohol kills it’. Look for the magic number EN1500 on the label – this means it’s just as good as alcohol at killing germs.
The Government advice is to thoroughly clean first with a general-purpose detergent, then disinfect with a solution of at least 1,000 parts per million active chlorine. This is advice is based on how they do it in the NHS, is well-meant but not really very practical. How do you know if the bleach solution (that’s where the chlorine comes from) has over 1,000ppm? Is a two-stage clean really practical? Do you mind everywhere smelling like a swimming pool?
Help is at hand. There are some very common EN standards for disinfectants and there are single-stage cleaning products that both clean and kill germs in a single action. That said, if a surface is filthy you need to clean it first then disinfect - because you can’t disinfect dirt – but for most cleaning a single stage is fine. Look for the magic numbers EN1276 or EN13697 on a cleaning product. Technically these are tests for activity against bacteria but if a product passes these it’ll kill coronaviruses easily. Also these are the two standards required for food surface sanitisers so many products carry this certification. The proper standard for virucidal activity is EN14476 so if you see that the product is fine too. Make sure you follow the instructions re any dilution or dwell times.
How to Clean Equipment
Obviously you need to take care using water-based chemicals on kit. Can you spray it on cloth / paper first? You might wish to consider an alcohol like isopropanol which will kill the virus but flashes off quickly and leaves no residue. But don’t use a hand gel – these usually contain various other ingredients such as aloe to stop skin drying out and will leave kit rather sticky.
This sounds like a plausible way to disinfect large areas and indeed it can be. But make sure you assess the need properly. The ‘fog’ is still water droplets – the machine doesn’t magically turn a dilute chemical into something else. ‘Dry’ fogging just means the droplets are smaller. It’s still water. If you’re thinking about fogging – say – a gallery or somewhere else full of sensitive equipment you might want to think twice and use a reputable supplier who understands this.
Also don’t forget the virus doesn’t fly around the air like a demented mosquito. It’s non-living and falls to the ground or other surfaces in respiratory droplets under gravity. Fogging is a way to disinfect surfaces efficiently, not the air.
A variation on this is electrostatics – where tiny droplets of disinfectant are electrically charged and ‘seek out’ surfaces. This can use 70% less chemical so it’s safer and more efficient.
UV kills germs. But it needs to be a certain type and intensity of UV (the proper term for the UV dose is the fluence – a term you’ll never need but we’ve included it for fun). Point is the type of UV that will definitely kill germs is also the type that will definitely cause serious eye damage and destroy skin. There are also practical questions such as what about areas in shadow?
We have seen clients using a proper UV cabinet designed for dental instruments as an extra step to disinfect earpieces and mics after they’ve been cleaned with an alcohol wipe but the sort of UV ‘wands’ you might see out there are basically novelty items that add very little to a disinfection process.
Heat kills germs too. And different types of germ are more or less susceptible to different temperatures and exposure time. Quite a lot of work has been done on the vulnerability of the coronaviruses to heat including the 2003 SARS so we’re not in the dark about this.
There are heat cabinets available for thermally disinfecting costume and most of these seem to go up to 60°C. Beware of reading science papers on this; a test tube in a lab water bath gets to temperature very quickly so careful interpretation is needed.
A costume in a cabinet takes far longer to heat through because air is a poor conductor of heat - that‘s why you can put your hand in a hot oven briefly but you get a burn instantly you touch the metal. We recommend at least two hours at 60°C to make sure garments get up to the correct temperature throughout.
Yes, steam kills germs too. But not any old steam. In hospitals and labs there are steam ovens called autoclaves and these run at very specific temperatures. They use superheated steam at a minimum of 121°C and 15psi to guarantee disinfection. This is not the same as wafting a steam wand at something. Yes, the coronavirus is not particularly hardy but unless it’s in an autoclave we suggest steam shouldn’t be your principal disinfection strategy.
How Long Does It Last?
This is a really difficult question. There are lots of studies which are seized upon by journalists and usually misinterpreted. How long the virus remains viable depends on the type of surface - but is hugely influenced by temperature, humidity, light and other factors. It’s complicated. Also some studies are looking for the presence of viral genetic material which is not the same as the presence of viable virus. And even if the study is testing for viable virus (as opposed to RNA in a PCT test), that doesn’t mean there’s enough to actually infect someone.
If you follow the common sense hygiene advice above the viability of the virus on a surface doesn’t really matter; you’ll kill the virus easily and needn’t worry about how long it takes to die of boredom.