Olfactory dysfunction in SARS-CoV-2 infection: Focus on odorant specificity and chronic persistence

Area of Science:

• Neurology
• Infectious Diseases
• Sensory Science

Background:

• Smell dysfunction (anosmia) is an early symptom of SARS-CoV-2 infection, often preceding respiratory symptoms.
• While often temporary, persistent smell loss can occur, with potential for chronic or permanent deficits.
• Limited knowledge exists regarding the specificity and long-term persistence of SARS-CoV-2-induced anosmia.

Purpose of the Study:

• To investigate the long-term olfactory performance in individuals recovered from SARS-CoV-2 infection.
• To determine if smell recovery is odorant-specific and to assess the persistence of smell deficits.
• To evaluate the timeline of smell persistence or reversal post-SARS-CoV-2 infection.

Main Methods:

• A longitudinal study involving 70 SARS-CoV-2 positive participants (IgG/IgM titers) and 348 controls.
• Smell testing using the 12-item Cross-Cultural Smell Identification Test (CC-SIT) was conducted 4 months post-infection.
• Statistical analysis of smell detection accuracy for individual odorants was performed.

Main Results:

• Four months post-infection, SARS-CoV-2 survivors showed reduced smell detection accuracy (80.0%) compared to controls (88.0%).
• A significant 9.1% decrease in odor detection accuracy was observed in the antibody-positive group.
• Recovery was notably delayed for strawberry, lemon, and soap odors, indicating specific olfactory deficits.

Conclusions:

• Smell performance remains impaired in SARS-CoV-2 patients even months after acute infection, irrespective of symptom severity.
• The ability to detect specific odors like strawberry, lemon, and soap is particularly affected.
• These persistent deficits suggest a potential for long-term or permanent olfactory impairment in a subset of patients.