Loss of smell may be best predictor of Covid-19: Research

Loss of smell may be the best predictor of Covid-19 among patients with symptoms of respiratory diseases, according to new research.

The findings of two new international studies, published in the journal Chemical Senses, show that there is frequent loss of smell in Covid-19 patients which often lasts for a long time.

Over 4,500 Covid-19 patients from a total of 23 nationalities responded to the researchers' questionnaire.

The studies found that the average loss of the sense of smell was 79.7 on a scale from 0-100, indicating a large to complete sensory loss.

"This emphasises how important it is to be aware of this symptom, as it may be the only symptom of the disease," said Alexander Wieck Fjaeldstad from Aarhus University in Denmark.

The research found that only around half of patients with a loss of smell got their sense of smell back after forty days.

Read: Could a smell test screen people for Covid-19?

"This differs from the picture we see with other viral infections and causes long-term discomfort for patients, both in relation to food and social contact, while at the same time causing them worry," Fjaeldstad said.

The researchers also found that the sense of taste was also significantly reduced, to 69.0 on a scale from 0-100, adding the remaining sense of feeling in the mouth was also reduced to 37.3 on a scale from 0-100.

"While the loss of smell in itself removes the ability to sense the aroma of food, the simultaneous loss of the other senses make it difficult to register what you're eating. Putting food in your mouth can therefore become a decidedly unpleasant experience," Fjaeldstad added.

The study is of interest both to patients suffering sensory loss as well as clinicians and researchers who work with diagnostics and following-up on Covid-19, the researchers said.

"It shows that the loss of smell is specific to Covid-19, which is both relevant in relation to recognising the infection, and because it indicates that the sense of smell is closely linked to how SARS-CoV-2 infects the body," Fjaeldstad said.

Previously, researchers have based the correlation between Covid-19 and the loss of the chemical senses on smaller studies,. The new studies collected large amounts of data from countries all over the world.

"The results are in line with our own national studies and pave the way for future studies on risk factors for permanent sensory loss, along with a better understanding of the consequences of these sensory losses for the patients,” Fjaeldstad said.