Among the long list of instructive COVID-19 symptoms, is the loss of taste and smell.
Although fever, labored breathing, and a dry cough are more commonly reported indicators of seasonal illness, neuropathies actually occur in over 60% of general upper respiratory infections and about 38% of the time in coronavirus infections specifically. The latter occurs even more regularly among younger populations. The reasons behind this correlation haven’t been thoroughly explored until now.
It has been suggested in the past that anosmia, or the loss of smell, may diminish one’s ability to distinguish between flavors. Recent research literature suggests that oral cavities are ideal locations for SARS-CoV-2 to inject host cells.
According to a new paper uploaded to the preprint service journal, medRxiv, COVID-19 causes damage to cells in the mouth. In addition to affecting our senses, this process further impacts a carrier’s transmissibility.
More directly, the salivary glands, tonsils, and tongue contain RNA and proteins epicentral to successful novel coronavirus transmission—serving as an “incubator” of sorts. This is why saliva is a viable route to infection and why receptors on the tongue responsible for taste are ineffective before viral clearance.
“Despite signs of infection, the involvement of the oral cavity in COVID-19 is poorly understood. To address this, single-cell RNA sequencing data-sets were integrated from human minor salivary glands and gingiva to identify 11 epithelial, 7 mesenchymal, and 15 immune cell clusters,” the authors wrote in the new paper. “Analysis of SARS-CoV-2 viral entry factor expression showed enrichment in epithelia including the ducts and acini of the salivary glands and the suprabasal cells of the mucosae. COVID-19 autopsy tissues confirmed in vivo SARS-CoV-2 infection in the salivary glands and mucosa. Saliva from SARS-CoV-2-infected individuals harbored epithelial cells exhibiting ACE2 expression and SARS-CoV-2 RNA.”
When samples were collected from participants experiencing a loss of taste, it became apparent that viral shedding and viral burden in saliva shared a doubt relationship with COVID-19 severity.
Patients eventually regained their sense of taste, but recovery time var drastically. For some, a complete recovery came after a few weeks, while others struggled for several months.
“Loss of smell or taste due to COVID-19 appears to last slightly longer compared to other upper respiratory infections. For example, loss of these senses due to a cold typically lasts for 3 to 7 days,“ Healthline reports
“A report by the Centers for Disease Control and Prevention (CDC) assessed the duration of symptoms in 274 adults that had mild COVID-19 symptoms. The median reported duration of loss of smell or taste was 8 days.“
Upon recovery, patients who had loss their sense of smell evidenced salivary antibodies against SARS-CoV-2 proteins.
“Saliva from SARS-CoV-2-infected individuals harbored epithelial cells exhibiting ACE2 expression and SARS-CoV-2 RNA. Matched nasopharyngeal and saliva samples found distinct viral shedding dynamics and viral burden in saliva correlated with COVID-19 symptoms including taste loss, the authors concluded.
“Our study shows that the mouth is a route of infections as well as an incubator for the SARS-CoV-2 virus that causes COVID-19.”
There are a host of other factors studied to contribute to the loss of taste or smell in COVID-19 patient samples. These include but are not limited to neurological conditions, including parkinson’s disease, smoking, blood pressure medications, antibiotics, and antihistamines.
“With COVID-19, a loss of taste or smell can come on suddenly and occur early, sometimes before other COVID-19 symptoms develop. Unlike other upper respiratory infections, a loss of smell or taste isn’t always associated with a runny or stuffy nose,”Healthline adds. “Most people who experience loss of smell or taste due to COVID-19 find that these symptoms resolve within a few weeks.”