A new study looking at the data of people who tested positive for COVID-19 backs up recent claims that the loss of the senses of smell and taste can be a symptom of the disease.
Earlier this month, preliminary findings in a preprint started making headlines because they suggested that the list of possible COVID-19 symptoms should include the loss of smell and taste.
That study assessed symptoms in 579 people who reported having tested positive for COVID-19 and 1,123 who reported having tested negative.
It found that 59% of those with COVID-19 said that they experienced the loss of smell and taste.
However, experts commenting on the study noted that more work was necessary to confirm that these sensory impairments could be a sign of COVID-19.
For example, according to Jane Parker, Ph.D., who is an associate professor in flavor chemistry at the University of Reading in the United Kingdom, “[t]his paper shows good preliminary (non-peer-reviewed) evidence that loss of smell and taste is likely to be a symptom of COVID-19, but its role as an early warning signal has not been confirmed.”
However, now, a new study that appears in the International Forum of Allergy & Rhinology seems to confirm that a significant number of people with COVID-19 experience loss of smell and taste as symptoms.
In the present study, researchers from the University of California (UC) San Diego Health in La Jolla evaluated data from 1,480 individuals who presented with influenza‐like symptoms and underwent testing for COVID‐19 between March 3 and March 29, 2020. All of these tests took place at UC San Diego Health.
The final analyses referred to information that 262 people provided, including 59 of the 102 people who tested positive for COVID-19 and 203 of the 1,378 who tested negative.
In general, the participants with COVID-19 had a mild form of the disease, and most of them did not require hospitalization.
Among the individuals who tested positive for COVID-19, 68% experienced loss of smell, and 71% experienced loss of taste.
In comparison, 16% of those who tested negative experienced smell loss, and 17% reported loss of taste.
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“Based on our study, if you have smell and taste loss, you are more than 10 times more likely to have [SARS-CoV-2] infection than other causes of infection,” says first author Dr. Carol Yan.
“We know [SARS-CoV-2] is an extremely contagious virus. This study supports the need to be aware of smell and taste loss as early signs of COVID-19.”
– Dr. Carol Yan
The researchers also found that, among the people with COVID-19 who experienced loss of smell and taste, the sensory impairment was usually “profound to complete.”
However, they also note that the recovery rate for these symptoms was high and that it tended to occur within 2–4 weeks of diagnosis.
“Our study not only showed that the high incidence of smell and taste is specific to COVID-19 […], but we fortunately also found that for the majority of people, sensory recovery was generally rapid,” Dr. Yan says.
“Among the COVID-19 patients with smell loss, more than 70% had reported improvement of smell at the time of survey, and of those who hadn’t reported improvement, many had only been diagnosed recently,” she continues.
The team also points out that people with loss of smell or taste tended to recover full use of these senses in about the same timeframe in which they recovered from COVID-19.
A separate observation also revealed another potentially interesting association, namely that individuals with flu-like symptoms who said that they were experiencing a sore throat usually tested negative for COVID-19.
Following on from these findings, staff at UC San Diego Health have decided to start including loss of smell and taste as potential indicators of COVID-19 when screening employees and visitors to the institutions and deciding which patients to test for a SARS-CoV-2 infection.
“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,” says Dr. Yan.