Loss of Taste and Smell in COVID-19: Association with Flu-Like Symptoms

Background

The rapid spread of the SARS-CoV-2 virus and concerns about viral transmission by outpatients with minimal or no symptoms underscore the importance of identifying early or subclinical symptoms of Covid-19 infection.

Two of these candidate symptoms include anecdotally reported loss of smell and taste . Understanding the timing and association of smell/taste loss in Covid-19 may help facilitate early detection and isolation of cases.

Introduction:

The Covid-19 pandemic caused by the SARS-CoV-2 virus continues to spread at an exponential rate with recent concerns of significant viral transmission through asymptomatic or mildly symptomatic patients.

A preliminary study from Iran showed a significant increase in new-onset anosmia since the Covid-19 outbreak. 2 An Italian report of 59 patients hospitalized with Covid-19 found that 33% reported a chemosensory disorder .

However, it is unclear whether these findings are unique to Covid-19 infections requiring hospitalization, causally related to Covid-19 infection, or simply due to a more widespread recognition of post-viral anosmia.

Understanding the timing and association of smell/taste loss and Covid-19 is critical, as patients with acute anosmia may be asymptomatic carriers of infection who may inadvertently facilitate the spread of the disease.

Methods

A single-institution cross-sectional study assessing patient-reported symptoms with a focus on smell and taste was conducted using an internet-based platform in adult subjects undergoing Covid-19 testing. Logistic regression was used to identify symptoms associated with Covid-19 positivity.

Results

A total of 1,480 patients with influenza-like symptoms underwent Covid-19 testing between March 3 and 29, 2020. Our study captured 59 of 102 (58%) Covid-19-positive patients and 203 of 1,378 (15%) Covid-19 - Negative patients.

Discussion

This study demonstrates the prevalence and unique presentation of chemosensory impairment in Covid-19 positive compared to Covid-19 negative individuals, both with flu-like symptoms.

We found a significant association between loss of smell/taste and Covid-19 infection, as these chemosensory alterations were at least 10 times more common in Covid-19 positive cases.

Of those who reported olfactory dysfunction , the loss was typically profound rather than mild. Despite the slightly higher incidence of ageusia compared with anosmia, we know that loss of taste is related to loss of smell and differences in reporting may be attributable to the few patients with basal rhinosinusitis-induced anosmia.

We have also shown that the majority of patients reported improved smell and taste at the time of the survey, usually less than two weeks after diagnosis. Likewise, overall disease symptoms improved or resolved during that time period. In selected cases (10%), patients reported early resolution of clinical symptoms without return of smell.

Overall, these findings may offer reassurance that patients with outpatient Covid-19 infection and associated anosmia/hyposmia can recover olfactory function within weeks, in parallel with the resolution of other disease-related symptoms. Of the Covid-19 positive respondents in this study, the majority did not require hospitalization and none required intubation, suggesting that a relatively mild subset of Covid-19 infection was captured.

This is in contrast to the hospital survey of Covid-19 infections by Giacomelli et al3, who reported rates of chemosensory loss at half the level of our subjects. This suggests that outpatient and inpatient cases of Covid-19 may follow fundamentally different clinical courses.

We hypothesize that perhaps outpatient cases are in part the result of viral shedding centered in the nose , while patients requiring hospitalization may be experiencing a more lung- centered viral infection leading to a higher rate of respiratory failure and the need of hospitalization.

Future studies are warranted to investigate this hypothesis because, if found to be true, beyond potential markers for detecting positivity for Covid-19 infection, anosmia/ageusia may have some prognostic potential for disease severity. disease.