Loss of smell could be a sign of milder case of coronavirus infection, UCSD Health says

An electron microscope image shows the coronavirus that causes COVID-19.
National Institute of Allergy and Infectious Diseases)

Researchers at UC San Diego Health have found that loss of smell related to the COVID-19 coronavirus suggests the resulting illness is more likely to be mild or moderate, a potential early indicator that could help health care providers determine which patients may require hospitalization.

The findings come in the wake of a similar study involving some of the same researchers, who found evidence linking loss of olfactory function to the coronavirus.

“Normosmia, or the normal sense of smell, is an independent predictor of admission in COVID-19 cases,” said Dr. Carol Yan, a rhinologist and head and neck surgeon at UCSD Health. “In previous research, we found that loss of olfactory function is a common early symptom, following fever and fatigue. What’s notable in the new findings is that it appears that loss of smell may be a predictor that a SARS-CoV-2 [coronavirus] infection will not be as severe, and less likely to require hospitalization.”

Yan’s latest study was conducted with colleagues Drs. Farhoud Faraji, Benjamin Ostrander and Adam DeConde — all physicians in the Department of Surgery at UCSD Health — and Divya Prajapati, a student in the UCSD School of Medicine.

“Patients who reported loss of smell were 10 times less likely to be admitted for COVID-19 compared to those without loss of smell,” said senior author DeConde, a rhinologist and head and neck surgeon.

Patients who were hospitalized for COVID-19 treatment were significantly less likely to report anosmia, or loss of smell (26.9% compared with 66.7% for infected people treated as outpatients).

Similar percentages were found for loss of taste, known as dysgeusia.

The researchers said the findings — published online April 24 in the journal International Forum of Allergy & Rhinology — possibly hint at some of the characteristics of the infection. If the virus initially concentrates in the nose and upper airway, where it impacts olfactory function, it may result in an infection that is less severe and sudden in onset, decreasing the risk of overwhelming the body’s immune response and causing respiratory failure and hospitalization.

A team of UC San Diego scientists is developing a COVID-19 antibody test and is hoping it will provide answers for immediate medical use against the coronavirus that causes the potentially deadly respiratory disease.

April 24, 2020

Additional, more expansive studies are needed for validation, the researchers said, but the findings can have important immediate applications for health care systems and patients.

“One of the immediate challenges for health care providers is to determine how to best treat persons infected by the novel coronavirus,” Yan said. “If they display no or mild symptoms, can they return home to self-quarantine or will they likely require hospitalization? These are crucial questions for hospitals trying to efficiently and effectively allocate finite medical resources.”

La Jolla Light staff contributed to this report.