Have you ever been sick and attempted to take comfort in your favorite foods, before realizing the sad truth: There's no point, because you can't taste them? Same goes with smell — you might not even be congested, but sometimes a sickness can just render you unable to smell even perfume right out of the bottle. This condition is called anosmia — otherwise known as "smell blindness" — and doctors think it might be a key to diagnosing the novel coronavirus (COVID-19) in people who aren't displaying other symptoms.
Since the COVID-19 outbreak began, a lot has been made of the fever and dry cough, the headaches and muscle aches associated with the illness. But as more cases crop up, one thing doctors all over the world — not to mention the Covid-stricken citizens of the Twitterverse — have noticed is that this coronavirus completely obliterates many patients' sense of smell, even if they aren't experiencing other symptoms. According to the New York Times, of 2,000 patients testing positive for coronavirus in South Korea, a third reported anosmia, whereas German doctors have communicated that, out of a group of 100 coronavirus patients, a full two-thirds of them experienced anosmia.
Anosmia (and its close associate ageusia, the complete loss of the tongue's ability to taste, and dysgeusia, the distortion of the sense of taste) is a common symptom in upper respiratory viruses. There are other causes for anosmia, too: Some people are mysteriously born without the ability to smell, and it's also normal for the olfactory system to go on the fritz as we age. Anosmia can be associated with head injuries or sinus conditions like rhinitis, nasal polyps and bacterial infections, but the reason for the loss of smell can vary depending on the root cause. For instance, a head injury can sever olfactory nerve fibers that act as pathways for smell information to get to the brain, whereas swelling in the sinuses from something like a bacterial infection or polyps can actually block the way of molecules carrying scent to the olfactory receptor cells. In the case of COVID-19 (and other, lesser bugs), the virus damages the smell receptor cells in the nose that help us detect odors, rendering the sense of smell very weak or completely useless, depending on the extent of damage.
Those who have anosmia also report a weakening of the ability to taste, which is normal. Although smell and taste are separate senses — our smell receptors are located high up in our nasal cavity and our taste receptors are found on our tongue — they are very closely tied. Our taste buds are pretty sturdy while our smell receptors are relatively delicate, but a lot of what we're experiencing when something has a distinctive flavor is the smell of the food rather than the taste. For instance, we can taste that mangos, bananas and raspberries are all sweet, but their distinctive flavors are the function of the smell of each fruit rather than anything our taste buds are picking up. When we lose our delicate smell receptors to an attacking virus, it's a bummer for a while, but our sense of smell almost always recovers.
According to a press release issued by the American Academy of Otolaryngology on March 22, 2020, anosmia and dysgeusia seem to be significant symptoms associated with the COVID-19 pandemic, even in those for whom no other symptoms are present. This means that, if in the course of the coming weeks, you notice your morning coffee tasting flat or smelling unimpressive, it might be time to self-quarantine.