One case of Covid-19 was considered mild if there was no evidence of viral pneumonia or loss of oxygen and the patient could recover at home.
The sense of smell reappeared after an average of 18 to 21 days, the study found, but about 5% of people had not recovered olfactory function in six months.
Covid-19 moderate to severe
By comparison, the study found that only 4% to 7% of people with moderate to severe symptoms of Covid-19 lost the ability to smell and taste.
People with moderate Covid-19 had “clinical signs of pneumonia,” the study said, such as cough, fever and difficulty breathing. Those with critical cases of the disease suffered from severe respiratory distress and were more likely to be older and have “hypertension, diabetes, gastric, renal, respiratory, cardiac, liver and neurological disorders”.
The study, published on Monday in the Journal of Internal Medicine, found a higher rate of olfactory dysfunction in younger patients compared to the elderly, but this association needs further analysis, the researchers said.
How to test your smell
Is there anything you can do at home to test if you are suffering from loss of smell? The answer is yes, using the “jellybean test”.
“You put the jujube in your mouth and chew it. Let’s say it’s a fruit flavored jujube: if you take the flavor plus the sweetness of the jujube, you’ll know it has a functional flavor, ”said Munger.
“Then, while you’re still chewing, suddenly release your nose. If you have a smell, you will suddenly smell all the odors and say ‘Oh! This is lemon gum’ or ‘Oh! This is cherry.’ It’s really kind of a very dramatic, quick and ‘wow’ response, “he explained.
“So if you can go from sweet and sour to full flavor and know what it tastes like,” said Munger, “then your sense of smell is probably in very good condition.”
The scientific name for this process is retro nasal smell, where odors flow from the back of the mouth, through the nasal pharynx and through the nasal cavity.
But what if you don’t have a jujube? You can also use other foods, said ear, nose and throat specialist Dr. Erich Voigt, director of NYU Langone Health’s sleep otorhinolaryngology division, in an earlier interview.
“The sense of pure smell would be if you could smell a specific substance that does not stimulate other nerves,” said Voigt. “If you can smell ground coffee or coffee being brewed, or if you can smell someone peeling an orange – that’s the smell.”
You have to be careful, though, because it’s easy to think you’re using your nose when you’re not, said Voigt.
“For example, ammonia or cleaning solutions, stimulate the trigeminal nerve, which is an irritating nerve,” he said. “And then people will think, ‘Oh, I can smell Clorox, I can smell ammonia, which means I can smell it.’ But no, that is not correct. They are not really smelling, they are using the trigeminal nerve. ”
Still not sure if you’re getting it right? Check the internet for medical based scratch and sniff tests.
Smell loss is common
Of course, not everyone who fails a smell test will get coronavirus. Any respiratory virus, such as a cold or flu, will temporarily affect your sense of smell and taste, sometimes even permanently.
“The amount of swelling that can occur in the nose due to the viral effect can prevent the smell particles from reaching the top of the nose, where the olfactory nerve is,” said Voigt. “When that swelling subsides, the sense of smell can come back.”
But there are also neurotoxic viruses, some of which are in the category of the common cold, said Voigt.
“If they are neurotoxic, that means they damage the olfactory nerve and it becomes essentially non-functional,” he added. “Many of these cases can recover the smell over time, but sometimes it is a permanent loss.”
A chronic partial or complete loss of smell is incredibly common, said Munger, affecting millions of Americans long before the new coronavirus broke out on the scene.
“About 13% of the population has a significant impairment in smell or taste,” he said.
In addition to the cold and flu, other causes of loss of smell include nasal polyps, tumors, neurodegenerative diseases such as Alzheimer’s or Parkinson’s and traumatic brain injury or head trauma, including whiplash.
“If someone was in a car accident or had a neck or head injury, it can also affect the small nerves that run from the brain to the nose,” said Voigt. “Therefore, a neck injury can also cause a permanent loss of smell.”
Loss of taste is commonly associated with loss of smell, because we depend on smell to identify flavors. But there can also be medical reasons: some medications can affect the taste; chemotherapy and radiotherapy can certainly disturb the taste; and there is physical damage, such as nerve damage during dental surgery.