Loss of the sense of smell is most likely to occur by the third day of infection with the novel coronavirus, according to a study of over 100 COVID-19 patients which may help public health experts better identify those carrying the virus without adverse symptoms.
The telephonic study, whose results were published in the journal Otolaryngology-Head and Neck Surgery, examined characteristics and symptoms of 103 patients who were diagnosed with COVID-19 over a six-week period.
The patients from Aarau, Switzerland provided data on the number of days they had COVID-19 symptoms, and the timing and severity of their loss of smell, said study co-author, Ahmad Sedaghat from the University of Cincinnati in the US.
Of the 103 patients, at least 61 per cent reported reduced or lost sense of smell, Sedaghat said, adding that the mean onset for reduction or loss in the sense of smell was 3.4 days.
"We also found in this study that the severity of the loss of smell is correlated with how bad your other COVID-19 symptoms will be," Sedaghat said.
"If the anosmia, also known as loss of smell, is worse, the patients reported worse shortness of breath, and more severe fever and cough," he added.
According to the scientist, the relationship between decreased sense of smell and the rest of the COVID-19 is something to be aware of.
"If someone has a decreased sense of smell with COVID-19, we know they are within the first week of the disease course, and there is still another week or two to expect," he added.
The findings indicated that a decreased sense of smell may be an indicator of patients early in the disease course as well as those who may go on to develop more severe symptoms, like shortness of breath, Sedaghat said.
He cautioned that while the loss of smell is an indicator of COVID-19, it's not the only factor.
"When you start to experience serious symptoms of COVID-19 which include shortness of breath and respiratory distress, that's when you should become alarmed," he said.
Younger patients and women in the study were also more likely to experience a decreased loss of smell, the study noted.
About 50 per cent of study patients experienced a stuffy nose and 35 per cent experienced a runny nose.
According to Sedaghat, this is important since previous studies indicated that these nasal symptoms were rare in COVID-19, and these symptoms were attributed to allergy and not the novel coronavirus.
"This just means that greater awareness is needed of COVID-19's nasal symptoms so people are not running around sneezing in public and thinking it is okay since this is just allergies," Sedaghat said.
"It very well could be COVID-19 and wearing masks as protective gear for others you encounter is a good idea," he added.
Understanding more about loss of smell and COVID-19 is important for a public health perspective, the scientist cautioned.
"No one is going to die because of a loss of the sense of smell and it's not the symptom that will kill anyone," he said, but adding that, "it is important because it helps us to identify these COVID-19 patients as asymptomatic carriers so they don't spread the disease to others."