The loss of smell was considered the hallmark symptom of COVID-19 in the early days of the pandemic when most patients reported it as the first symptom they noticed since catching SARS-CoV-2.

But as the virus continues to evolve, researchers observed that smell disruption has become less common. Many new patients did not experience the symptom while battling the virus.

A study published in SAGE Journals in May reported the decreasing incidence of chemosensory disruptions with the newer coronavirus variants.

For the study, the researchers utilized data from the 3,678,214 patients enrolled in the database. After screening, 616,318 met the inclusion criteria for the study.

The team found that people who contracted the alpha variant of SARS-CoV-2 had a 50% probability of smell loss. The percentage fell to 44% for the delta variant, and it dropped further to 17% for the omicron variant.

Valentina Parma, a psychologist at the Monell Chemical Senses Center in Philadelphia, Pennsylvania, told Nature they were no longer flooded with inquiries about the symptom as they used to be in the first two years of the pandemic.

However, smell disruption has remained a cause for concern among many people, especially those who contracted the virus earlier in the pandemic.

People who contracted the older strains of the virus somehow continued to experience chemosensory effects months and years after their initial bout with the disease.

A 2021 study published in the journal Rhinology followed 100 people who suffered mild COVID-19 and 100 people who repeatedly tested negative for the virus. The researchers found that 46% of those who had COVID-19 still had smell problems a year later.

The study could mirror what’s happening globally. Worldwide, more than 500 million cases of COVID-19 have been diagnosed. When compared to the study, this could mean that tens of millions of people have been struggling with lingering smell problems.

As of late, scientists are still working on better understanding and finding treatments for the COVID-19-triggered issue. In February, a team of researchers claimed a non-cell-autonomous disruption of nuclear architecture in COVID-19 patients could be the potential cause of the symptom.