ISLAMABAD: The sudden loss of smell and taste, once a distinct hallmark of many COVID-19 cases and a reliable early indicator of infection, has become a less common symptom of the virus, according to growing research. While it was prevalent in around 50% of cases early in the pandemic, recent data indicates that only a small fraction of new patients reported this symptom in more recent waves.
The findings are based on analysis of a comprehensive dataset of medical records collected by the National Institutes of Health (NIH) from across the United States for COVID-19 research purposes.
“In the past, people were quite aware that if they lost their sense of smell due to a cold, it might be an indicator of COVID-19. However, this is no longer a reliable sign,” said Dr. Evan Reiter, medical director of VCU Health’s Smell and Taste Disorders Center.
Dr. Reiter led a study, published in the journal Otolaryngology-Head and Neck Surgery, which investigated the likelihood of patients with COVID-19 experiencing a loss of smell and taste.
While chemosensory loss (loss of smell and taste) was reported in an estimated 50% of cases early in the pandemic, recent research suggests a prevalence of only 3% to 4% in more recent waves, such as the Omicron variant.
Similar trends have been observed in other studies as well. Researchers from University College London found that the proportion of cases reporting loss of taste or smell significantly decreased after the emergence of the Omicron strain in 2021.
Changes in COVID-19 Symptoms
As the virus evolves and immunity from infections and vaccinations builds, symptoms associated with COVID-19 have changed. Variants like Omicron have led to shifts in symptomatology, with symptoms more closely resembling those of other respiratory illnesses.
Researchers are actively investigating the reasons behind persistent loss of taste and smell after COVID-19 infections. Studies have suggested that the immune response, particularly T cells, could be targeting nerve cells in the nose even after the virus has cleared, leading to ongoing inflammation.
Understanding the underlying mechanisms behind these symptoms could potentially pave the way for new treatments aimed at promoting nerve cell regeneration and recovery.
For now, doctors have limited options to treat patients experiencing loss of smell. Olfactory training, exposure to pleasant smells, and certain drug treatments are some of the approaches used. While many patients eventually recover their sense of smell over time, some may require intervention or treatment to aid in the recovery process.
