A new study supports the notion that loss of either smell or taste may be an early warning sign of COVID-19.
Anecdotal accounts of smell and taste loss associated with COVID-19 have been reported worldwide, but without formal studies, scientists could not determine how common the symptom was among those infected. Now, a new study published online April 12 in the journal International Forum of Allergy & Rhinology has found that smell and taste loss appear to be common initial symptoms in patients with mild infections.
People with smell loss can often still sense different tastes, like saltiness or sweetness, but cannot identify specific flavors, according to the medical reference site Merck Manual. Therefore, people with smell loss often report losing their sense of taste, as well.
"Based on our study, if you have smell and taste loss, you are more than 10 times more likely to have COVID-19 infection than other causes of infection," Dr. Carol Yan, an otolaryngologist and head and neck surgeon at the University of California, San Diego Health, said in a statement.
While fever is still the most common first symptom of COVID-19, "this study supports the need to be aware of smell and taste loss as early signs of COVID-19," Yan said. Along with fatigue, smell and taste loss appear to be common first symptoms in a sizable group of patients, she added.
Yan and her colleagues screened data from 1,480 patients with flu-like symptoms who underwent COVID-19 testing at UC San Diego Health in March. Of 102 patients who tested positive for the virus, 59 participated in the smell-loss study. An additional 203 people who tested negative also participated in the study, allowing the researchers to discern whether smell loss was fairly unique to COVID-19 patients.
Of the COVID-19-positive patients in the study, about 68% said they experienced smell loss and 71% reported taste loss, as compared with 16% and 17% of negative patients, respectively. Among the COVID-19 patients with smell or taste loss, the decrease in sensation was often "profound, not mild," according to the UC San Diego statement. However, the majority of patients recovered their sense of smell and taste within about 2 to 4 weeks, around the time they'd recovered from infection.
"Among the COVID-19 patients with smell loss, more than 70 percent had reported improvement of smell at the time of survey and of those who hadn't reported improvement, many had only been diagnosed recently," Yan said.
No participants in the study required hospitalization or invasive breathing support, such as intubation. If social-distancing measures were not in place, such individuals could potentially spread the infection to others in their communities, despite not experiencing intense symptoms. Smell and taste loss should be noted as potential signs of COVID-19 in people who otherwise feel well, given that those with mild symptoms contribute heavily to the virus' spread, Yan said.
"It is our hope that with these findings other institutions will follow suit and not only list smell and taste loss as a symptom of COVID-19, but use it as a screening measure for the virus across the world," she said.
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Originally published on Live Science.
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