Rhinology in review: from COVID-19 to biologicals.

We look back at the end of what soon will be seen as an historic year, from COVID-19 to real-world introduction of biologicals influencing the life of our patients. This review describes the important findings in Rhinology over the past year. A large body of evidence now demonstrates loss of sense of smell to be one of the most common symptoms of COVID-19 infection; a meta-analysis of 3563 patients found the mean prevalence of self-reported loss to be 47%. A number of studies have now shown long-term reduced loss of smell and parosmia. Given the high numbers of people affected by COVID-19, even with the best reported recovery rates, a significant number worldwide will be left with severe olfactory dysfunction. The most prevalent causes for olfactory dysfunction, besides COVID-19 and upper respiratory tract infections in general, are trauma and CRSwNP. For these CRSwNP patients a bright future seems to be starting with the development of treatment with biologics. This year the Nobel prize in Medicine 2021 was awarded jointly to David Julius and Ardem Patapoutian for their discoveries of receptors for temperature and touch which has greatly enhanced our understanding of nasal hyperreactivity and understanding of intranasal trigeminal function. Finally, a new definition of chronic rhinitis has been proposed in the last year and we have seen many papers emphasizing the importance of endotyping patients in chronic rhinitis and rhinosinusitis in order to optimise treatment effect.

The effect of coronaviruses on olfaction: systematic review.

BACKGROUND: Unlike other respiratory viruses, SARS-CoV-2 causes anosmia without sinonasal inflammation. Here we systematically review the effects of the 7 known human coronaviruses on olfaction to determine if SARS-CoV-2 distinctly affects the olfactory system. METHOD: PubMed, EMBASE, Web of Science, bioRxiv, medRxiv and DOAJ were searched for studies describing pathophysiological, immunohistochemical, cytological and clinical data. RESULTS: 49 studies were included. Common cold coronaviruses lead to sinonasal inflammation which can cause transient and chronic loss of smell. MERS-CoV entry receptors were not found in the nasal mucosa and it did not impair olfaction. SARS-CoV-1 had low affinity for its receptor ACE2, limiting olfactory effects. Anosmia is frequent in SARS-CoV-2 infections. SARS-CoV-2’s entry factors ACE2 and TMPRSS2 are expressed in the nasal respiratory epithelium and olfactory supporting cells. SARS-CoV-2 appeared to target the olfactory cleft while diffuse nasal inflammation was not observed. Damage of the olfactory epithelium was observed in animal models. Alternative receptors such as furin and neuropilin-1 and the similarity of viral proteins to odourant receptors could amplify olfactory impairment in SARS-CoV-2 infection. CONCLUSIONS: The pathophysiology of anosmia in SARS-CoV-2 infection is distinct from other coronaviruses due to preferentially targeting olfactory supporting cells. However, SARS-CoV-2 does not cause sinonasal inflammation in spite of preferred entry factor expression in the nasal respiratory epithelium. This raises doubts about the attention given to ACE2. Alternative receptors, odourant receptor mimicry and other as yet unknown mechanisms may be crucial in the pathogenesis of anosmia in SARS-CoV-2 infection. Further studies are warranted to investigate infection mechanisms beyond ACE2.

How a small virus changed our world and the special role of anosmia.

In January 2020 we encountered the first news on a novel coronavirus (SARS-CoV-2) infecting the population of the Chinese city Wuhan and resulting for some patients in a potentially deadly pneumonia. Currently, coronavirus disease 2019 (COVID-19) is spreading rapidly around the globe. For many years we have been warned that we would face a new pandemic, most likely with a zoonotic virus. For COVID-19 it was shown that transmission can occur via droplets and aerosols that can remain in the air for some hours and also via contaminated surfaces. Extra risks have been suggested to exists for aerosol producing surgery in sinus- and skull-base surgery. Ongoing transmission is especially difficult to prevent when the pathogen can be transmitted during the incubation period before the patient experiences symptoms. In March, Claire Hopkins and colleagues warned the rhinologic community and later health authorities about the significant increase in anosmia (and dysgeusia) related to (often further) asymptomatic COVID-19 and pointed to the possibility of recognizing COVID-19 patients by unexplained anosmia without other symptoms.