Coronavirus affects the body in a plethora of different ways. It infects the upper respiratory tract leading to a cough and shortness of breath, it causes congestion that blocks sinus drainage passages and leads to headaches, it triggers the body’s production of cytokines leading to fever and inflammation and for many people, it messes around with their sense of smell and taste.
Our ability to detect smells and odours comes from a little, specialised piece of tissue in our nasal cavities known as the olfactory epithelium. This patch, whilst it appears small, actually contains around 50 million nerve cells covered in tiny hairs. These are called cilia and they have receptors that can bind the molecules that enter your nose and dissolve into the mucus that lines your nasal passages. This binding triggers an electrical signal that travels to the olfactory bulb, which is a sort of neuron relay station. They are then passed along the olfactory nerve, which carries the signal to your brain. Every odour we experience produces a unique firing pattern of neurons, allowing us to distinguish between similar smells.
A lot of cases of anosmia are caused by malfunctions in some part of this olfactory system. There are many known respiratory viruses that interfere with our ability to smell and it seems that coronavirus is able to do this not by attacking the olfactory nerve cells directly but the cells that support them.
The researchers at Harvard who discovered this are encouraged by their findings as it suggests the virus is unlikely to cause permanent damage. “I think it’s good news” said Sandeep Robert Datta, one of the co-authors of the Harvard paper, “because once the infection clears, olfactory neurons don’t appear to need to be replaced or rebuilt from scratch.” That means anosmia should be temporary, disappearing once the infection has been cleared.
But if coronavirus affects the olfactory neurons, why is that so many people find they can’t taste either? Well, only some of what we taste comes from our taste buds. There are hundreds of these taste buds found in each of the thousands of the little bumps, or papillae, on your tongue. These are able to detect the sensations of bitterness, sweetness, sourness, saltiness and umami. However, most of what we taste actually comes from the aroma of food. These odours travel down our nasal passages, where we detect them, rather than coming from your mouth. If you bite into a strawberry, your tongue will detect that it is sweet, but it is the aromas in your nose that tell you it’s strawberry flavoured.
It was about three days after my positive test result that I noticed I couldn’t taste or smell things as well as I normally could. I stopped being able to taste cups of tea (a realisation that any British person will find deeply upsetting) and I didn’t notice the burning toast that nearly set off our fire alarm. Soon I couldn’t taste or smell anything much at all. Ageusia, the scientific term for partial or complete loss of the ability to taste, is a pretty perplexing experience.
Once you lose your ability to taste, what do you eat? I had a lot of people in my house joking that it would be the perfect time to go on a health kick. “Eat nothing but kale,” one of them laughed, “you won’t be able to tell how bad it is.” That is one potential strategy, but it disregards the multifaceted role that food plays in our modern lives. Most of us are fortunate enough to be able to select what we eat largely based on what we feel like and what we will enjoy; food is not simply a fuel, but is instead a means of socialising, a response to emotions, a way to fill the time (and once you’re in isolation – you really aren’t short on time). And on top of that food is a multisensory experience. Especially if you can’t smell, as I couldn’t, the texture of the foods and the way they look becomes a whole lot more important. Just because you can’t taste it, that doesn’t mean you will be satisfied after eating a big bowl of kale.
So, what did I eat? Everyone who I have spoken to has had a slightly different experience of losing their taste and smell, but I personally found that the foods I wanted to eat were low on flavour and big on texture. This might sound counter-intuitive when your tasting capacity is reduced, but I found something comforting about eating foods that didn’t taste of much even when I could taste everything. I particularly liked foods with very distinctive textures; things like crisp iceberg lettuce, airy rice cakes, buttery toast, crunchy bowls of cereal and creamy avocado (I was very surprised to find out that even at my lowest tasting ability, I could also still taste avocado – I found my middle-class silver lining).
Now it has been a week since my other coronavirus symptoms stopped, but I still cannot taste or smell much at all. In spite of that, I am still hopeful. The research does seem to suggest that it will come back eventually. If not, I’ll have to eat my words. Luckily, they won’t taste of much.