Some COVID-19 coronavirus patients are reporting an unusual symptom: anosmia, or loss of smell, with recently published research and guidance from professional societies indicating this may be an early or overlooked symptom of the infection.
The Royal College of Surgeons of England noted data from where patients developed anosmia or hyposmia. And they said two out of three confirmed cases in Germany developed the symptom and, for 30% of mild cases in South Korea, it was the major presenting symptom.
Some of this data was recently published in the medical literature, with a letter to the editor in Clinical Infectious Diseases by Andrea Giacomelli, MD, of the University of Milan, and colleagues, noting hospitalized patients admitted for COVID-19 "complained of ."
They interviewed 59 patients and found 20 reported at least one taste or olfactory disorder, while 11 patients reported both. Moreover, 12 patients said they reported this symptom prior to hospital admission, while eight said it developed during the hospital stay. Taste alterations were more likely to be reported prior to hospitalization, and women were more likely to report this than men. They also found patients with at least one olfactory or taste disorder were younger (median age 56 vs 66 without, respectively).
"Our survey shows that [olfactory and taste disorders] are fairly frequent in patients with [COVID-19] infection and may precede the onset of full-blown clinical disease," they wrote, adding further research is necessary to determine if these unspecific symptoms could represent a "clinical screening tool" for patients with few symptoms.
The American Academy of Otolaryngology-Head and Neck Surgery also recently proposed anosmia and dysgeusia, or loss of taste, be added to the for COVID-19 infection.
Eric Holbrook, MD, of Massachusetts Eye and Ear and Harvard Medical School in Boston, who was not involved with the research, noted this is a common symptom of a cold or upper respiratory infection, where nasal congestion results in enough swelling to result in an obstruction in nerves responsible for sense of smell. But this data has not yet been explored in COVID-19 patients.
"Is it an early sign; is it that it jumps out to people more because they don't have other symptoms, but notice their sense of smell," he told 鶹ý. "We don't know how many patients have true smell loss, we don't know where it starts in the whole disease process or how long it lasts."
Holbrook said other viral infections can cause anosmia, and in a small subgroup of patients, that loss of smell can be long-lasting or even permanent. But he added for mild COVID-19 infection, "a lot of reports" say this resolves after 2 weeks.
However, given these patient reports, he agreed anosmia should be recognized as a potential indicator of COVID-19 infection, and patients with these symptoms should be directed to their primary care physician or a COVID-19 testing area or hotline in their region.
"If I get called and asked to respond to a patient with a sudden smell loss, I would ask about fever, chills, or muscle aches" and if that is the case, Holbrook said he recommends follow-up with a primary care physician, as well as doing "measures for isolation" when patients have these symptoms, and then testing to prevent the spread of the virus.
Holbrook added reports of anosmia have not been widely documented in more severe cases of COVID-19, especially patients requiring mechanical ventilation, so data has tended to skew towards the milder cases.
In the future, he said he would like to see research on whether COVID-19 patients have smell loss at a greater frequency than people with the same symptoms, without COVID-19, as well as tracking patients to see if it only occurs in mild cases or if it occurs in all patients.