Loss of smell was a symptom which was only later added to the official list of symptoms despite the large number of people declaring it as a possible warning.
However, one of the commonly reported symptoms by many patients infected with the novel coronavirus is the loss of smell. Most patients had reported being unable to distinguish scents during their battle with the infection.
Scientists have now discovered why coronavirus causes some patients to lose their sense of smell.
The study included 145 individuals aged between one month and 65 years with mild to moderate Covid-19 who were studied in three groups: children younger than five years, children five to 17 years, and adults 18 to 65 years. Health experts also said that anosmia could be a reliable and batter way to predict whether a person has the disease, other than other prevalent symptoms such as cough and fever.
Their data suggest that a temporary loss of function of supporting cells in the olfactory epithelium (tissue in the nasal cavity involved in smell), which indirectly causes changes to olfactory sensory neurons, is what may cause Covid-19-related anosmia.
"Biopsies of infected tissue that show the virus does indeed infect and replicate in sustentacular cells would be more helpful". However, the researchers wrote that although they observed a "response" to the coronavirus infection among patients with high levels of the virus in the muscles surrounding their hearts, "this was not associated with an influx of inflammatory cells". An global team of researchers led by neuroscientists at Harvard Medical School (HMS) recently identified the olfactory cell types that are most vulnerable to infection by SARS-CoV-2 (the virus that causes Covid-19). Also, olfactory sensory neurons do not express the gene that encodes the angiotensin-converting enzyme 2 (ACE2) receptor protein, which is used by the novel coronavirus to enter human cells.
"Our findings indicate that the novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of supporting cells", said senior study author Sandeep Robert Datta, a Harvard Medical School neurobiology professor.
But the news is still good, as it implies that in most cases, indirect neural damage caused by coronavirus is highly unlikely to be permanent or lead to long-lasting consequences, as "once the infection clears, olfactory neurons don't appear to need to be replaced or rebuilt from scratch", the researcher noted.
Some countries have been successful such as Norway and Denmark but many, including South Korea, have had to close schools after reopening due to spikes in infections.
The first new study investigated 100 recovered COVID-19 patients (median age of 49 years old), an average of 71 days after initial diagnosis. The team utilized a machine-learning algorithm to study data from more than 1,600 patients in the United States and the United Kingdom.
Of the 100 patients recently recovered from COVID-19, 67 (67%) recovered at home, while 33 (33%) required hospitalization. The team added the entries of an additional 1,047 patients in the U.S., U.K., and Sweden in May. In April, the symptom was officially added to the Centers for Diseases Control and Prevention's list of Covid-19 symptoms. The third cluster composed of headaches, loss of appetite, loss of smell, diarrhea, sore throat, chest pain, but without cough.