Anosmia with Influenza and Rhinovirus
Yes, anosmia can occur with both influenza and rhinovirus infections, though it is significantly less common than with COVID-19. In a direct case-control comparison, only 12.5% of influenza patients experienced new onset olfactory or taste disturbances compared to 39.2% of COVID-19 patients 1.
Evidence for Rhinovirus-Associated Anosmia
Rhinovirus is a documented cause of postviral olfactory dysfunction (PVOD). In patients presenting with PVOD, rhinoviruses were detected in nasal discharge in 42% of cases (10 of 24 patients), with specific serotypes identified including HRV-40, HRV-75, HRV-78, and HRV-80 2.
Key Clinical Characteristics of Rhinovirus-Related Anosmia:
- Rhinovirus can cause olfactory dysfunction through mechanisms independent of nasal obstruction, as acoustic rhinometry showed significant improvement while olfactory testing remained impaired 2
- The dysfunction can be persistent, with some patients experiencing anosmia or dysosmia for at least 6 months after initial presentation 2
- Rhinovirus-induced olfactory loss varies in severity and time course among affected individuals 2
Evidence for Influenza-Associated Anosmia
Influenza does cause anosmia, but at substantially lower rates than COVID-19. The comparative data shows that olfactory/taste disturbances occurred in 12.5% of influenza-positive patients versus 39.2% in COVID-19 patients 1.
Historical Context:
- Viral upper respiratory infections, including influenza, account for 20-25% of specialist clinic presentations with olfactory disturbances 3
- Other viruses linked to anosmia include parainfluenza, coronavirus (non-SARS-CoV-2), and Epstein-Barr virus, affecting up to 20% of the adult population, which is considerably less than SARS-CoV-2 4
- Long-term serious olfactory loss can result from colds and flu, with patients experiencing dysfunction for more than 6 months showing serious impairment of olfactory abilities 5
Clinical Implications
When evaluating patients with new-onset anosmia, consider the following diagnostic approach:
- COVID-19 testing should be prioritized in patients with sudden onset taste/smell loss, especially during pandemic periods 6
- Obtain detailed history focusing on temporal relationship with viral infections and associated symptoms 6
- Perform objective olfactory testing using standardized methods such as the University of Pennsylvania Smell Identification Test (UPSIT) 6
- Conduct thorough nasal examination for signs of obstruction or inflammation 6
Important Caveats:
The presence of anosmia with nasal congestion suggests a conductive mechanism, while anosmia without nasal obstruction symptoms (as seen in 87.1% of COVID-19 patients with smell disorders) suggests a different pathophysiologic mechanism 1. This distinction is clinically relevant when differentiating between viral etiologies.
Rhinovirus and influenza can both cause persistent olfactory dysfunction lasting months, requiring long-term follow-up and consideration of olfactory training as primary treatment for at least 3-6 months 6, 2.