Seven out of ten patients were affected by each of these two symptoms, concludes the study published in the Journal of Intern Medicine and carried out on more than 1,400 patients with an infection by the new coronavirus confirmed by a screening test.
The other most common symptoms were stuffy nose (67.8%), cough (63.2%), and fatigue (63.3%), followed by muscle pain (62.5%), runny (60.1%) and loss of taste (54.2%). In contrast, fever was only reported by less than half of patients (45.4%).
This first epidemiological survey on European patients with a non-severe form of COVID-19 was launched by the International Federation of ENT Societies (IFOS), to assess the frequency of symptoms of loss of smell (anosmia) and taste (ageusia), reported by some patients since the arrival of the pandemic on the European continent.
Their preliminary results published in early April had shown the frequency of these symptoms, little described until then by studies carried out in Asia.
Their comprehensive study carried out in five European countries (France, Belgium, Italy, Spain and Switzerland) confirms that loss of smell is “a specific symptom” of COVID-19, and not just the consequence of nasal obstruction.
“The ability of COVID-19 to invade the olfactory bulb and, therefore, the central nervous system, is probably a lead” to explain anosmia, points out the Foch hospital.
Anosmia and ageusia have been poorly described in studies of Chinese patients, which mainly reported fever, cough, and respiratory discomfort as symptoms of COVID-19.
The study conducted by IFOS believes that this difference can be explained by the fact that the Chinese studies involved hospitalized patients, with more severe forms of infection.
The authors also hypothesize that successive genetic mutations in the coronavirus could be the cause of different symptoms, and that European populations have a higher level of angiotensin 2 converting enzyme, or ACE2, which acts as a receptor for the coronavirus.
They also point out that the frequency of symptoms varies according to age and gender.
Thus, young patients more often present with ENT disorders (ear, nose and throat) while elderly patients often present with fever, fatigue and loss of appetite.
Cough and fever are found more in men, with women being more affected by loss of smell, headaches and a stuffy nose.