Dubai, United Arab Emirates (CNN)–Imagine waking up one morning after recovering from “Covid-19” to find that your coffee smells like unwashed socks, and orange juice has a metallic taste.
This is a good thing, as it indicates that your sense of smell is still working.
And your ability to smell can completely disappear in a condition called anosmia.
Taste and smell are related to each other, so food may be flavorless.
Your appetite and enjoyment of life may decrease, and previous studies have shown that this can lead to nutritional deficiencies, cognitive decline, and depression.
And without smells, you probably wouldn’t notice fires, natural gas leaks, toxic chemicals, or spoiled food and drink.
This is the case for the roughly 5% of COVID-19 survivors globally, who now develop long-term problems with taste and smell, according to a 2022 study.
More than two years after the outbreak of the pandemic, researchers found that about 15 million people may have problems with smell recognition, while 12 million people may have problems with taste.
Support groups such as AbScent and Fifth Sense are mobilized to help, provide hope, tips for smell training and even recipes to boost appetite.
Smell training encourages people to smell essential oils twice a day, says rhinologist and professor of otolaryngology, head and neck surgery at Stanford University School of Medicine, Dr. Zara Patel.
As science learns more about how COVID-19 attacks and disrupts the sense of smell, rhinoplasty specialist and associate professor of otolaryngology and head and neck surgery at Vanderbilt University Medical Center in Nashville, Dr. Justin Turner, said: “I think we’ll see more targeted interventions.
Increasing cases due to the Corona virus
People have lost their sense of smell and taste for centuries.
Viruses of the common cold, the common flu, nasal polyps, thyroid disorders, and other conditions can damage the ability to smell and taste, sometimes permanently.
Aging is also a major cause of the loss of the sense of smell, as the ability of olfactory neurons to regenerate declines.
When the virus that causes Covid-19 invaded our lives, the condition, which was considered relatively rare among people under 50, spread dramatically, affecting all ages.
In fact, loss of smell was so prevalent at the start of the pandemic that it was considered an early sign of COVID-19, even in the absence of other symptoms.
A study published in May found that 17% of people lost their sense of smell when infected with the omicron variant, which became the dominant variant of the virus that causes COVID-19 in late 2021 (and that could change again if the virus mutates).
When compared, people who got sick with the original two variants, alpha and beta, were 50 percent more likely to lose their sense of smell or taste.
The delta variant was just as bad, with 44% of people affected, according to the study.
How the damage occurred
At first, scientists believed that Covid-19 affects the nerve cells in the nose that are responsible for transmitting smells from the environment to the brain.
These neurons are located in the olfactory bulbs at the top of each nostril, and send axons to unique sensory points in the brain.
And studies soon discovered that the virus never enters those neurons, and instead attacks the support cells that provide nourishment and protection to neurons from birth.
And unlike many other cells, the nerve cells in the nose regenerate every two to three months.
“It’s possible that injury to these supportive cells will have some kind of long-term effect on the ability of those neurons to regenerate themselves over time,” Turner said.
He added, “This is one of the reasons why we sometimes see a delayed effect. People may experience anosmia, recover, and then experience a second wave of anosmia, parosmia, or other symptoms.”
“Parosmia” is the medical term for distorted, often disgusting odors, Patel says.
And science continues to discover ways to attack the virus.
A February study found that it may also damage olfactory receptors on the surface of nerve cells in the nose.
There may also be a genetic factor, as a January study discovered a mutation in two overlapping genes, UGT2A1 and UGT2A2. This mutation plays a role in odor metabolism.
Those with this mutation may be more likely to lose their sense of smell, but more studies are needed to determine the link between the virus and the genes, if it does exist.