When Does Loss of Smell Occur With COVID-19?
Loss of smell, known medically as anosmia, has emerged as one of the telltale symptoms of COVID-19. Studies show a significant percentage of COVID-19 patients experience some degree of anosmia during their illness. For many, the loss of smell occurs early on in their infection and may be one of the first symptoms they notice.
Understanding when smell loss develops and how long it lasts can provide important clues in detecting COVID-19. Let's take a closer look at what research tells us about the timing and duration of anosmia in COVID-19.
Anosmia Often Appears Early In COVID-19 Illness
Multiple studies have found that anosmia tends to appear relatively early on in the course of COVID-19 infection, typically during the first 3-4 days of symptoms.
In a European study of over 2000 COVID-19 patients, 86% reported loss of smell as one of their symptoms. Of those with anosmia, nearly 75% experienced it as their first symptom, appearing before any signs of fever or respiratory problems.
A study out of Iran found similar results - among a group of nearly 100 COVID-19 patients with anosmia, loss of smell presented before any other symptoms in 65% of cases.
Researchers believe inflammation caused by SARS-CoV-2, the virus that causes COVID-19, leads to swelling and blockage in the olfactory cleft, home to smell receptor neurons. This disruption in the early stages of infection is likely responsible for the early onset smell loss seen in many patients.
Anosmia May Persist After Other Symptoms Resolve
For some who lose their sense of smell from COVID-19, this symptom lingers even after all other symptoms have cleared. It has been reported as one of the most persistent symptoms in patients recovering from mild to moderate illness.
One study from Italy evaluated over 200 COVID-19 patients 30 days after onset of symptoms. While most reported improvements in other symptoms, 33% still had loss of smell at the 30-day mark.
A study out of Iran found similar results - among post-COVID patients, anosmia persisted in 26% one month after falling ill. This makes smell loss one of the most stubborn symptoms, often lasting into the post-viral or recovery phase.
Experts believe this extended anosmia may be due to ongoing inflammation or lasting damage to olfactory neurons. The virus may rupture supporting cells needed for proper functioning of smell receptors.
Smell Loss May Last for Weeks or Months
For those who do regain their sense of smell after COVID-19, the process is often gradual. Studies show recovery times ranging from weeks to months before smell function returns to normal.
A European study published in the Journal of Internal Medicine tracked smell recovery in nearly 100 COVID-19 patients. Results showed:
- After one month, 27% had fully recovered smell function
- After two months, 56% had fully recovered smell function
- After 6 months, 96% had fully recovered smell function
The findings confirm that while most do eventually recover, the process is slow and can take months. Around 4% had not fully regained baseline smell function 6 months out.
A study in Switzerland followed nearly 100 COVID-19 patients specifically for issues with taste and smell. They found:
- After 1 month, 36% had fully recovered smell
- After 6 months, 96% had fully recovered smell
Again pointing to a gradual recovery period that lasts weeks or months for many dealing with post-COVID smell loss.
When Does Loss of Taste Occur With COVID-19?
Loss of taste, known medically as ageusia, has also been strongly linked to COVID-19 infection. Like loss of smell, taste dysfunction often occurs early and may persist into the later stages of illness.
Understanding the timing of taste loss and how recovery unfolds is important for detecting possible COVID-19 and managing ongoing symptoms.
Ageusia Frequently Appears Soon After Initial Infection
Numerous studies have shown taste loss occurring very early in the course of COVID-19, sometimes even before smell loss sets in.
A study published in the Journal of Korean Medical Science found that among COVID patients reporting chemosensory dysfunction, 59% experienced taste loss as their first symptom. Loss of smell developed shortly after for most patients.
Analysis from a hospital in Milan, Italy found that 50% of COVID-19 patients reported taste loss, with the symptom appearing after an average of 3 days post-infection. Anosmia and other symptoms developed soon after.
Early onset loss of taste points to rapid attack on the taste bud cells soon after the virus takes hold in the body. This aligns with current understanding of COVID-19 pathology.
Ageusia May Persist As Other Acute Symptoms Resolve
As with loss of smell, taste dysfunction has been shown to linger longer than other COVID-19 symptoms and may remain into the post-viral phase.
In a study published in the British Journal of Oral and Maxillofacial Surgery, nearly half of COVID patients surveyed reported ongoing issues with taste loss two months after recovering from the acute illness.
Data from a study in Ireland found taste dysfunction lasting more than 6 weeks in 13% of patients who were otherwise recovered from COVID-19.
The prolonged dysfunction may be due to damage to taste bud cells from viral replication. These cells turnover every 10-14 days, so regeneration and recovery of full taste perception may require multiple cycles.
Most Regain Taste Within 3-4 Weeks
Despite potentially lingering for weeks or months, most COVID-19 patients do eventually regain their sense of taste. Studies generally show recovery occurring within 1-2 months for a majority of people.
In a small study of 24 COVID patients with loss of taste, researchers found:
- After 14 days, 50% had fully recovered taste
- After 21 days, 75% had fully recovered taste
A study from China reported similar trends - taste recovery within 20 days for most hospitalized COVID patients experiencing the symptom.
While timelines vary from person to person, these results indicate many can expect to regain full taste function within 3-4 weeks of onset. However, a subset do appear to take longer to fully heal.
What Causes Extended Loss of Smell and Taste in COVID-19?
For those suffering from persistent loss of smell or taste long after other COVID-19 symptoms have disappeared, what explains these lingering sensory disruptions?
Research points to a few key factors:
Ongoing Inflammation and Congestion
Inflammation triggered by SARS-CoV-2 can cause swelling and clogging in the nasal passages, mouth, and upper airways. This congestion may persist for weeks after initial infection, maintaining disruption to smell and taste perception.
Damage to supporting cells in the olfactory and taste bud linings may also slow regeneration, extending dysfunction.
Loss of Sensory Cells
Direct viral damage to sensory cells in the nasal cavity and mouth appears responsible for many cases of enduring smell and taste loss.
One study found COVID infection reduced the number of olfactory sensory neurons by 50-75%. Loss of taste bud cells has also been documented.
Regeneration of these vital sensory cells often takes weeks or months, explaining the prolonged dysfunction many experience.
Central Nervous System Disruption
There is some evidence that COVID-19 may in rare cases cause inflammation or damage to smell and taste pathways in the brain.
One study found subtle changes in brain imaging of COVID patients with persistent anosmia, indicating possible central nervous system effects.
While not well documented yet, neurological impairment is plausibly linked to sensory loss lasting months after other recovery in some patients.
Tips for Coping with Extended Loss of Smell and Taste
Losing your sense of smell
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.
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