A small study out of Europe is the first to look at how smell loss associated with COVID-19 differs from that caused by a severe cold or the flu—and the findings bolster the theory that the coronavirus infects the brain and central nervous system, per a press release. A group of smell disorder experts conducted smell and taste tests on a group of 30 participants: Ten of them had had COVID-19 for about two weeks, 10 had had bad colds, and 10 served as controls. The goal, per study lead Carl Philpott of Norwich Medical School, was to figure out how a symptom common to both illnesses actually differs. Per their study in the journal Rhinology, they found three main deviations, in addition to the fact that the smell loss tended to be more severe: With COVID-19 smell loss, the patient can breathe freely, typically doesn't have a stuffed or runny nose, and can't detect sweet or bitter tastes.
Philpott explains that "it has previously been suggested that the COVID-19 virus affects the central nervous system, based on the neurological signs developed by some patients. There are also similarities with SARS, which has also been reported to enter the brain, possibly via smell receptors in the nose. Our results reflect, at least to some extent, a specific involvement at the level of central nervous system in some COVID-19 patients." And he calls the results "very exciting," because they suggest smell and taste tests could be put to use in a diagnostic manner. Though they wouldn't be precise enough to replace the common swab test, "they could provide an alternative when conventional tests are not available or when rapid screening is needed, particularly at the level of primary care, in emergency departments, or at airports," he says. (Read more coronavirus stories.)