“The nose contains about 400 receptors that work like keys on a piano. A specific smell, like coffee, is like a tune across multiple keys. It’s a pattern of responses across those receptors, which we learn to associate with a particular smell. With damage, these receptors sometimes get cross-wired—like a switchboard operator putting cables in the wrong hole. Many viral illnesses cause temporary loss of smell—anosmia. But because of COVID-19, many millions of people have suffered sudden and complete smell loss. Roughly 85% recover in a few weeks, but there’s a fraction of people for whom the loss lasts much longer. This has drawn attention to the importance of smell and how smell loss can severely impact quality of life.
“COVID-19 seems to cause smell loss in a unique way that involves the ACE2 receptor. Since the CDC added smell loss to the official symptom list, there has been a race to better understand smell perception and loss. Here at Penn State, we have launched a smell awareness campaign; we’ve distributed single-odor peel-and-sniff cards across the university for students, faculty, and staff to do a quick smell check. Our team also has a separate research study with eight different odors that might work as a comprehensive diagnostic test, but that would need to be FDA-approved before it is ready for use by health providers.
“As new expertise and smell-testing tools are developed, one hope is that doctors might routinely check smell in your annual checkup in the same way they now check hearing and sight, even when this pandemic ends and SARS-CoV-2 becomes an endemic virus.” —SI