Anosmia, or the loss of one’s sense of smell, has previously been identified as an early warning sign of the mild cognitive impairment that can lead to Alzheimer’s disease. Now, along with ageuisa—the loss of taste—it’s been cited as one of the most common symptoms experienced by those who have contracted COVID-19.
While they weren’t commonly reported in Wuhan, China, during the early stages of the pandemic, these conditions are often the only symptoms experienced by people with mild cases. However, they can develop after other symptoms appear and remain after most signs of illness are gone.
In the United Kingdom, anosmia and ageuisa have been stronger predictors
of COVID-19 than fever. As of April 1 out of 400,000 people reporting one or
more symptoms on a mobile tracking app developed at King’s College London, 18% had lost their sense of smell or taste and 10.5% were experiencing fever.
Dr. Zara Patel, a Stanford associate professor who researches olfactory disorders, explains that COVID-19 is just one of a variety of viruses that can attack the trigeminal and olfactory nerves and their surrounding tissue. This type of inflammation, either occurring directly around the nerve in the nasal lining or within the nerve itself, is what causes the complete or partial loss of smell.
According to Patel, people who have a family history of neurological diseases
are more vulnerable to damage from viral-induced inflammation and may be
less capable of recovering from anosmia, ageusia, or hyposmia, the decreased ability to taste certain types of foods. For this reason, Patel urges seeking treatment, which could include olfactory training as well as medication, as early as possible for symptoms that persist after recovery.
Anyone who has experienced loss of smell or has recently recovered from an upper respiratory infection is encouraged to participate in the Global Consortium for Chemosensory Research survey at gcchemosensr.org. A joint effort between 500 clinicians, neurobiologists, data scientists, cognitive scientists, sensory researchers, and technicians from 38 countries, the survey aims to help uncover how the virus is transmitted—and how to prevent its spread—by asking participants to rate their ability to smell and taste before, during, and after their illness.
A similar survey called SmellTracker has been developed in neurobiologist Noam Sobel’s laboratory at the Weizmann Institute of Science in Israel. Participants are asked to pick five household items from a list that includes vanilla, peanut butter, mustard, garlic, and toothpaste and rate the intensity of their odor and taste over time.
The algorithm then creates an “olfactory fingerprint” that measures olfactory
perception and mirrors an individual’s unique genome. Such fingerprints predict genetic features linked to the olfactory system, such as aspects of immune regulation.
Scientists estimate that there are currently eight active strains of COVID-19, and Sobel and his colleagues believe that anosmia may be a differentiating symptom. While the specter of losing our senses of smell and taste, even for a short time, is anxiety-inducing for any wine professional, keep in mind that those who have experienced these symptoms report recovery times spanning ten days to several weeks, with two-thirds of surveyed patients at King’s College London reporting improvement in three weeks.