COVID-19, the disease caused by the new Coronavirus, generally manifests itself with symptoms such as a cold, sore throat, cough, and fever, or in more serious cases, with pneumonia and breathing difficulties.
Those who have studied such patients have detected acute alterations in both smell and taste, and in particular a reduction or loss of both senses in a large number of cases. This phenomenon has also been observed in a high number of swab-positive individuals who have had an absence of other symptoms associated with COVID-19.
But what is the relationship between SARS-CoV-2 coronavirus infection and taste and smell?
We discuss this with Professor Alberto Albanese, Head of Neurology I in Humanitas.
“The COVID-19 infection represents a new disease and we are learning new information every day. The first set of data, coming from China, South Korea and Italy, indicates a frequency of anosmia (loss of smell) in 30-60% of the affected. This phenomenon has also been reported by doctors who have been infected with the virus. Consequently, it is reasonable to believe that there could be a relationship between the increasing number of reports about the loss of smell and the current pandemic due to COVID-19”, explained the Professor.
Loss of taste and loss of sense of smell
“Most of the flavors we experience are perceived through the nose more than through the tongue. The flavors spread in the mouth produce a mixed sensation of taste and smell, responsible for the wider perception of taste. The loss of taste is therefore a natural consequence of the loss of smell.
Epidemiological studies about the loss of the sense of smell are complicated by the presence of respiratory symptoms with rhinitis, coughing, and irritation of the mucous membranes, making it difficult to create a direct link between COVID-19 and the human olfactory system”, continued Professor Albanese.
The new studies
“However, it is well known that the olfactory route is the gateway to several respiratory viruses to the central nervous system, such as herpesviruses types 1 and 6, rabies and influenza viruses. An initial study showed that the olfactory system could represent a privileged access route to our organism for some coronaviruses and this could also occur with the SARS-CoV-2 responsible for COVID-19. The olfactory epithelium, in fact, also hosts trigeminal nerve endings, through which the virus could gain access to the brain.
At Humanitas, we are developing our own project with the aim of identifying the patients where this mechanism may have occurred. The hypothesized scenarios are the following:
- In some subjects the virus could infect the olfactory system and reach the olfactory cortex of the brain.
- In other subjects the virus could infect the lungs, either through the direct action of droplets breathed in from the air, or through a “shower” mechanism, in which the viral particles fall downwards from the olfactory mucosa to the lungs.
- Finally, in a small number of patients, the virus may affect a larger part of the brain, either through diffusion from the olfactory cortex or through circulation.
Some preliminary data indicates a difference in gender and age for the loss of smell and taste caused by SARS-CoV-2: the phenomenon would preferentially affect women – who generally have more benign forms of respiratory infection – and younger people.
Scientific research is focused on understanding the different behaviours of this new virus,” Prof. Albanese concluded.