Biochemical and Other Mechanisms Associated With Olfaction and Taste Abnormalities in Covid-19

Mechanisms of olfaction and taste abnormalities in covid-19

  • Loung V Umedani
  • Quratulain Javaid
Keywords: Biochemical, neurological, manifestation, COVID 19, mechanisms.


Coronavirus (SARS-CoV-2) spreads from its initial nasal reservoir to produce respiratory problems and
neurological manifestations. Viral spike protein-S binds with host receptor angiotensin-converting enzyme
2 with the assistance of membrane fusion protease. Average smell and taste disorders prevalence was 18.8%
and 14.1% respectively.
The objective of this narrative retrospective study was to explore mechanisms underlying olfactory and
gustatory manifestations. For obtaining novel information, we selected articles from January 2021 to January
2023. We searched terms like neurological manifestations, anosmia, loss of taste in COVID-19, and SARSCoV-2 as keywords using PubMed. After scrutiny, we excluded articles with accessory and non-relevant
information and finally selected 23 articles.
Various immune mechanisms like cytokine storm and direct neuroinvasions result in neurological manifestations.
Role of various micro RNAs in molecular pathology point towards future research to explore epigenetic
neuropathological mechanisms to help in designing novel therapeutic remedies. Global awareness and
vaccination protocols had greatly reduced occurrence of disease.
Key Words: Ageusia, anosmia, biochemical, COVID-19, mechanisms


Drosten C, Günther S, Preiser W, et al. Identification of a novel coronavirus in patients with severe acute respiratory syndrome. N Engl J Med. 2003;348(20):1967–1976.

Monchatre-Leroy E, Boué F, Boucher J-M, et al. Identification of alpha and beta coronavirus in wildlife species in France: bats, rodents, rabbits, and hedgehogs. Viruses. 2017;9(12):364.

Li B, Si H-R, Zhu Y, et al. Discovery of bat coronaviruses through surveillance and probe capture-based next-generation sequencing. mSphere, 2020;5:1.

Khaled Habas, Chioma Nganwuchu, Fanila Shahzad, Rajendran Gopalan, Mainul Haque, Sayeeda Rahman, Anwarul Azim Majumder & Talat Nasim. Resolution of coronavirus disease 2019 (COVID-19), Expert Review of Anti-infective Therapy, 2020;18(12):1201-1211.

Wang M, Bu X, Fang G, Luan G, Huang Y, Akdis CA, Wang C. et al. Distinct expression of SARS‐CoV‐2 receptor ACE2 correlates with endotypes of chronic rhinosinusitis with nasal polyps. Allergy 2021;76:789–803.

Kanberg N, Ashton NJ, Andersson LM, Yilmaz A, Lindh M, Nilsson S. Neurochemical evidence of astrocytic and neuronal injury commonly found in COVID-19. Neurology. 2020;95(12):e1754–e1759.

Butowt R, von Bartheld CS. Anosmia in COVID-19: Underlying Mechanisms and Assessment of an Olfactory Route to Brain Infection. Neuroscientist. 2021;27(6):582-603.

Moraschini V, Reis D, Sacco R, Calasans-Maia MD. Prevalence of anosmia and ageusia symptoms among long-term effects of COVID-19. Oral Dis. 2022 Nov. 28 Suppl;2:2533-2537.

Scotto G, Fazio V, Lo Muzio E, Lo Muzio L, Spirito F. SARS-CoV-2 Infection and Taste Alteration: An Overview. Life (Basel). 2022;12(5):690.

Farid H, Khan M, Jamal S, Ghafoor R. Oral manifestations of Covid-19-A literature review. Rev Med Virol. 2022 Jan;32(1):e2248.

Gu J, Gong E, Zhang B, Zheng J, Gao Z, Zhong Y, et al. Multiple organ infection and the pathogenesis of SARS. J Exp Med 2005;202:415-424.

Kim JE, Heo JH, Kim HO, Song SH, Park SS, Park TH, et al. Neurological complications during treatment of Middle East respiratory syndrome. J Clin Neurol 2017;13:227-233.

Najafloo R, Majidi J, Asghari A, Aleemardani M, Kamrava SK, Simorgh S, Seifalian A, Bagher Z, Seifalian AM. Mechanism of Anosmia Caused by Symptoms of COVID-19 and Emerging Treatments. ACS Chem Neurosci. 2021 Oct 20;12(20):3795-3805.

Brola W, Wilski M. Neurological consequences of COVID-19. Pharmacol Rep. 2022;30:1–15.

Poncet-Megemont L, Paris P, Tronchere A, Salazard JP, Pereira B, Dallel R, et al. High prevalence of headaches during Covid-19 infection: a retrospective cohort study. Headache. 2020;60(10):2578–2582.

Pun BT, Badenes R, Heras La Calle G, Orun OM, Chen W, et al. COVID-19 Intensive Care International Study Group. Prevalence and risk factors for delirium in critically ill patients with COVID-19 (COVID-D): a multicenter cohort study. Lancet Respir Med. 2021;9(3):239–250.

Klok FA, Kruip MJHA, van der Meer NJM, Arbous MS, Gommers DAMPJ, Kant KM, et al. Incidence of thrombotic complications in critically ill ICU patients with COVID-19. Thromb Res. 2020;191:145–147.

Khatana SAM, Groeneveld PW. Health disparities and the coronavirus disease 2019 (COVID-19) pandemic in the USA. J Gen Intern Med. 2020;35(8):2431–2432.

Keddie S, Pakpoor J, Mousele C, Pipis M, Machado PM, Foster M, et al. Epidemiological and cohort study finds no association between COVID-19 and Guillain–Barré syndrome. Brain. 2021;144(2):682–693.

Klein, Robyn S. Mechanisms of coronavirus infectious disease 2019-related neurologic diseases. Current Opinion in Neurology. 2022;35(3):392-398.

Chen R, Wang K, Yu J, Howard D, French L, Chen Z, et al. The spatial and cell-type distribution of SARS-CoV-2 receptor ACE2 in human and mouse brain. Front. Neurol. 2021;11:573095.

Marshall M. COVID and the brain: researchers zero in on how damage occurs. Nature. 2021;595(7868):484‐485.

Brann DH, Tsukahara T, Weinreb C, et al. Non‐neuronal expression of SARS‐CoV‐2 entry genes in the olfactory system suggests mechanisms underlying COVID‐19‐associated anosmia. Sci Adv. 2020;6(31):eabc5801.

Ribeiro DE, Oliveira‐Giacomelli Á, Glaser T, et al. Hyperactivation of P2X7 receptors as a culprit of COVID‐19 neuropathology. Mol Psychiatry. 2021;26(4):1044‐1059.

Boscolo-Rizzo P, Borsetto D, Fabbris C, Spinato G, Frezza D, Menegaldo A, et al. Evolution of altered sense of smell or taste in patients with mildly symptomatic COVID-19. JAMA Otolaryngology–Head & Neck Surgery. 2020;146(8):729-32.

Samaranayake LP, Fakhruddin KS, Panduwawala C. Sudden onset, acute loss of taste and smell in coronavirus disease 2019 (COVID-19): a systematic review. Acta Odontol Scand. 2020;78(6):467-473.

Uginet M, Breville G, Hofmeister J, Machi P, Lalive PH, Rosi A, et al. Cerebrovascular Complications and Vessel Wall Imaging in COVID-19 Encephalopathy—A Pilot Study. Clin Neuroradiol. 2022 Mar;32(1):287-293.

Du F, Liu B, Zhang S. COVID-19: the role of excessive cytokine release and potential ACE2 down-regulation in promoting hypercoagulable state associated with severe illness. J Thromb Thrombolysis. 2021 Feb;51(2):313-329.

Wu P, Duan F, Luo C et al. Characteristics of ocular findings of patients with coronavirus disease 2019 (COVID-19) in Hubei Province, China. JAMA Ophthalmol. 2020:138(5);575–578.

Korkmaz MÖ, Egilmez OK, Özçelik MA. Otolaryngological manifestations of hospitalised patients with confirmed COVID-19 infection. Euro Archiv Oto-Rhino-Laryngol. 2021;278(5):1675-1685.

Cantuti-Castelvetri L, Ojha R, Pedro LD, et al. Neuropilin-1 facilitates SARS-CoV-2 cell entry and infectivity. Science 2020 Nov 13;(370):856-860.

Prajapat M, Sarma P, Shekhar N, Avti P, Sinha S, Kaur H, Kumar S, Bhattacharyya A, Kumar H, Bansal S, Medhi B. Drug targets for corona virus: A systematic review. Indian J Pharmacol. 2020 Jan-Feb;52(1):56-65.

Shi CS, Nabar NR, Huang NN, Kehrl JH. SARS-coronavirus open reading frame-8b triggers intracellular stress pathways and activates NLRP3 inflammasomes. Cell Death Discov. 2019;5:101.

Charnley M, Islam S, Bindra GK, Engwirda J, Ratcliffe J, Zhou J, Mezzenga R, Hulett MD, Han K, Berryman JT, Reynolds NP. Neurotoxic amyloidogenic peptides in the proteome of SARS-COV2: potential implications for neurological symptoms in COVID-19. Nat Commun. 2022 Jun 13;13(1):3387.

Heneka MT, Golenbock D, Latz E, Morgan D, Brown R. Immediate and long-term consequences of COVID-19 infections for the development of neurological disease. Alzheimer’s Res. Ther. 2020;12(1):69.

Schurink B, Roos E, Radonic T, Barbe E, Bouman CSC, de Boer HH, et al. Viral presence and immunopathology in patients with lethal COVID-19: a prospective autopsy cohort study. Lancet Microbe. (2020);1:e290–9.

Zhang L, Zhou L, Bao L, Liu J, Zhu, H, Lv Q, Liu R, Chen W, Tong W, Wei Q, et al. SARS-CoV-2 crosses the blood–brain barrier accompanied with basement membrane disruption without tight junctions alteration. Signal Transduct. Target. Ther. 2021 Sep 6;6(1):337.

Bayati A, Kumar R, Francis V, McPherson PS. SARS-CoV-2 infects cells following viral entry via clathrin-mediated endocytosis. J. Biol. Chem. 2021 Jan-Jun;296:100306.

Hao W, Ma B, Li Z, Wang X, Gao X, Li Y, et al. Binding of the SARS-CoV-2 spike protein to glycans. Sci Bull (Beijing) 2021;66(12):1205–14.

Dunai C, Collie C, Michael BD. Immune-Mediated Mechanisms of COVID-19 Neuropathology. Front Neurol. 2022 May 19;13:882905.

Afzali B, Noris M, Lambrecht BN, Kemper C. The state of complement in COVID-19. Nat Rev Immunol. 2022 Feb;22(2):77-84.

Poudel A, Poudel Y, Adhikari A, Aryal BB, Dangol D, Bajracharya T, et al. D-Dimer as a Biomarker for Assessment of COVID-19 Prognosis: D-Dimer Levels on admission and Its Role in Predicting Disease Outcome in Hospitalized Patients with COVID-19. PLoS One 2021 Aug 26;16(8):e0256744.

Sui J, Noubouossie DF, Gandotra S, Cao L. Elevated Plasma Fibrinogen Is Associated With Excessive Inflammation and Disease Severity in COVID-19 Patients. Front Cell Infect Microbiol (2021);11:734005.

Billoir P, Alexandre K, Duflot T, Roger M, Miranda S, Goria O, et al. Investigation of Coagulation Biomarkers to Assess Clinical Deterioration in SARS-CoV-2 Infection. Front Med (2021);8:670694.

How to Cite
Umedani, L., & Javaid, Q. (2024). Biochemical and Other Mechanisms Associated With Olfaction and Taste Abnormalities in Covid-19. Annals of Jinnah Sindh Medical University, 10(1), 30-37. Retrieved from
Review Articles