The War Against Germs

Jun 23, 2020

While the business has been closed for the pandemic, I’ve been brushing up on health and safety. Cleaning has an important role in protecting against all kinds of biohazards, including SARS-Cov2, the virus that causes Covid19.

Does cleaning kill bacteria, fungi and viruses? No, but it removes the dirt that harbours the germs. Bacteria and fungi don’t just grow in dirt, they feed on it. What we call “dirt” includes all kinds of things: soil, food remnants, human skin, animal hair, human and animal body secretions… Obviously, dirt is a party palace for microbes. Some microbes create bad smells and some cause diseases. The first step in getting rid of them is to clean!

Sanitising is a step up from cleaning. Sanitising reduces the number of microbes on a surface, i.e. it kills a lot of them, but some will remain. We often clean and sanitise at the same time, by cleaning with products that contain antibacterial agents. Toilet gel and antibacterial surface spray are example of products we use to clean and sanitise. If you choose a perfumed product, the bottle label will probably also say it “deodorises”.

Disinfecting is more extreme than sanitising: disinfecting kills all or most of the microbes on a surface. Disinfectants are not cleaning agents, they are killing agents. It is recommended that we always clean before disinfecting. This is because dirt prevents disinfectants from working properly. Spraying disinfectant onto a dirty surface simply disinfectants the top layer of the dirt, and there will be plenty of germs hiding underneath. Another problem is that disinfectant reacts with organic material in the dirt, effectively using up its “killing power” on the dirt instead of on the microbes.


The only way to be sure everything on a surface is dead is to sterilize it. In laboratories autoclaves are used to sterilize equipment, but at home you can sterilize in a pressure cooker.

Disinfection is the next best thing to sterilizing. When used properly, some disinfectants will kill up to 99.9999% of microbes (which for practical purposes means all of them). A disinfectant that kills 99.9999% is a Log Kill 6 product – a powerful beast that probably won’t be available in your local supermarket. You might be able to buy one that claims to kill 99.99% of bacteria, a Log Kill 4 product, which is still very strong. Most sanitisers are only Log Kill 3, capable of killing 99.9% of bacteria.

Dettol Laundry Cleanser is a sanitiser you can add to your load of washing. If you know something in there is germ-ridden, put some of this in the fabric softener dispenser, and you’ll feel much better!

On the back label of the bottle, it says this product will kill coronavirus (it doesn’t specify which coronavirus). The instructions for anti-virus action are different: pre-soaking with a stronger concentration of the sanitiser.


Although bacteria, fungi, protozoans and viruses are all tiny, at the microscopic level they’re very different. A virus is technically not a living organism at all because it can’t grow or replicate outside of a living cell. Bacteria and fungi can grow in dirt on surfaces, whereas viruses just survive on surfaces until they die. The survival time for a virus outside a host (for SARS-Cov2 the host is a human being or possibly a bat) can vary – it depends on the type of surface, the temperature, the humidity.

When we use a sanitiser or disinfectant, we can’t assume it will be effective against every kind of germ. An antibacterial product will kill bacteria, though not necessarily all bacteria. These products are usually tested against some common types of disease-causing bacteria. You have to check the bottle to see if the product kills viruses and fungi as well as bacteria. “Broad spectrum” products are effective against many things. Bleach (hypochlorite) is broad spectrum: it is an oxidising agent and will indiscriminately attack any type of organic matter, including bacteria, fungi and viruses.

The virus everyone is worried about is SARS-Cov2, a coronavirus. These days when people talk about Coronavirus they invariably mean SARS-Cov2, although it isn’t the only coronavirus (the virus that causes the common cold is also a coronavirus). If you want to be absolutely sure of killing SARS-Cov2 of your surfaces, you need to buy a disinfecting product that has been tested against this virus. It will have this code on the container: EN14476:2013+A2:2019 Annex A*.

The specialist antiviral disinfectants are being used in hospitals and in some factories, schools and public areas. They leave a residue on surfaces that will continue killing viruses for at least 24 hours. As chemicals go, these products aren’t particularly toxic to humans – some of them can be sprayed onto food contact surfaces.

In our homes we have many items we don’t want to expose to disinfectant. You probably don’t want to put chemicals on your silk scarf or your antique furniture. Luckily direct sunlight is a fantastic disinfecting agent – so hanging things on the clothesline is a great option. In any case, viruses can’t replicate outside of a living thing, and will eventually die on surfaces. As a general rule of thumb, if you leave an object for 3 days before handling it, then it should be safe.