• Users Online: 2144
  • Home
  • Print this page
  • Email this page
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 

   Table of Contents      
Year : 2023  |  Volume : 9  |  Issue : 1  |  Page : 50-51

Anosmia and dysgeusia as markers of severity and prognosis in COVID-19

Study Group for the Diagnosis and Treatment of COVID-19 in Veracruz, Veracruz, Mexico

Date of Submission18-Sep-2022
Date of Decision01-Dec-2022
Date of Acceptance07-Dec-2022
Date of Web Publication24-Mar-2023

Correspondence Address:
Luis Del Carpio-Orantes
12 de Octubre 603, Veracruz, ZC 91900
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/bc.bc_65_22

Rights and Permissions

How to cite this article:
Carpio-Orantes LD, Garcia-Mendez S, Diaz JS, Solis-Sanchez I, Aguilar-Silva A. Anosmia and dysgeusia as markers of severity and prognosis in COVID-19. Brain Circ 2023;9:50-1

How to cite this URL:
Carpio-Orantes LD, Garcia-Mendez S, Diaz JS, Solis-Sanchez I, Aguilar-Silva A. Anosmia and dysgeusia as markers of severity and prognosis in COVID-19. Brain Circ [serial online] 2023 [cited 2023 Jun 4];9:50-1. Available from: http://www.braincirculation.org/text.asp?2023/9/1/50/372441

It is currently known that the SARS-CoV-2 virus, the etiological agent of COVID-19, has a great neurotropism, infecting neural cells of the olfactory bulbs and surrounding areas, thus reaching the central nervous system, in addition to other pathways such as hematogenous, conditioning a wide range of neurological symptoms, including anosmia and dysgeusia.[1]

However, there have been disparities in the results, since some study groups have reported that the presence of anosmia with or without dysgeusia is a factor of severity and poor prognosis, while other groups mention the opposite, its presence portends a good prognosis in patients, there have even been systematic reviews and meta-analyses in this regard.[2],[3],[4]

Quantitative smell testing demonstrates that decreased smell function (hyposmia), but not always anosmia, is a major marker for SARS-CoV-2 infection and suggests the possibility that smell testing may help, in some cases, to identify COVID-19 patients in need of early treatment or quarantine.[5]

Dysgeusia is a prevalent qualitative gustatory impairment that may affect food intake and quality of life. The facial (VII), glossopharyngeal (IX), and vagus (X) nerves are the three cranial nerves responsible for sensing taste. Typically, dysgeusia is considered a general term for all taste disorders. In addition, dysgeusia may be a symptom of underlying systemic conditions such as diabetes mellitus, chronic kidney disease, respiratory infections (currently includes COVID-19), and nutritional deficiencies.[6]

With COVID-19, the rate of incidence of olfactory dysfunction in patients has been varied from 29.64% to 75.23% and the rate of incidence of taste dysfunction among people can be different from 20.46% to 68.95%.[7]

We present a study in which we found that anosmia was associated with greater severity and poor prognosis, while dysgeusia was associated with less severity and better prognosis.[8]

However, what could be the factors that influence these symptoms to have a positive or negative correlation in severity and prognosis?

The answer probably has several aspects associated with the ecological triad.

  Host Factors Top

It is mentioned that patients who have risk factors such as obesity, diabetes, or hypertension, as well as primary or secondary immunosuppression, could suffer more severe conditions and favor greater neurotropism; It has also been shown that there are other receptors in the brain in addition to angiotensin-converting enzyme 2 (ACE 2) that can act to facilitate the neuroinvasion of SARS-CoV-2, such as the Basigin (BSG), neuropilin-1 (NRP1), transmembrane serine protease 11A (TMPRSS11A), and furin receptors, but the amount of them varies from one individual to another. Other studies that have worked with single-cell sequencing revealed that ACE2 is expressed in supporting cells, stem cells, and perivascular cells, rather than in neurons. These findings suggest that CoV-2 infection of nonneuronal cell types causes anosmia and related disorders in odor perception in COVID-19 patients.[9],[10]

  Agent Factors (SARS-CoV-2) Top

Per se, this betacoronavirus has a great affinity for the central nervous system in such a way that it is considered neurotropic, neuroinvasive, and neurovirulent, however, some variants have a greater capacity than others, highlighted in this area the ancestral variant D614G, followed by the Delta variant (B.1.617.2) and finally by Omicron BA1 (B.1.1.529), the latter presenting the least neurotropism in vitro and in vivo studies.[11]

  Environmental Factors Top

It is mentioned that some geographical regions have favored greater severity and involvement with subsequently increased neurotropism than other regions; Asian regions initially did not report neurological symptoms such as anosmia or dysgeusia, these appeared as the pandemic was conquering European and later American regions with the following globalization of these symptoms; Although other regions such as Iran reported these alterations since the beginning of the pandemic. Sudden onset of olfactory dysfunction was reported in 76.24% of the participations and persistent anosmia in 60.90% since the start of the COVID-19 epidemic. In addition, 80.38% of participants reported concomitant olfactory and gustatory dysfunctions. Factors such as temperature, humidity, and air quality have been identified as facilitators of the transmission of SARS-CoV-2.[12],[13]

We consider that the conjunction of these factors as a whole is what predisposes to greater or lesser severity of the disease and therefore of neurotropism, and according to these characteristics, symptoms such as anosmia or dysgeusia, among others, can behave as good or bad prognosis in different populations. In the same way, there are racial, genetic, and geographical variations that predispose some populations to have these more entrenched characteristics and that, having a higher incidence of these symptoms, act as severity factors.

  References Top

Yachou Y, El Idrissi A, Belapasov V, Ait Benali S. Neuroinvasion, neurotropic, and neuroinflammatory events of SARS-CoV-2: Understanding the neurological manifestations in COVID-19 patients. Neurol Sci 2020;41:2657-69.  Back to cited text no. 1
Dev N, Sankar J, Gupta N, Meena RC, Singh C, Gupta DK, et al. COVID-19 with and without anosmia or dysgeusia: A case-control study. J Med Virol 2021;93:2499-504.  Back to cited text no. 2
Mutiawati E, Fahriani M, Mamada SS, Fajar JK, Frediansyah A, Maliga HA, et al. Anosmia and dysgeusia in SARS-CoV-2 infection: Incidence and effects on COVID-19 severity and mortality, and the possible pathobiology mechanisms – A systematic review and meta-analysis. F1000Res 2021;10:40.  Back to cited text no. 3
Silu M, Mathur NP, Kumari R, Chaudhary P. Correlation between anosmia and severity along with requirement of tocilizumab in COVID-19 patients. Indian J Otolaryngol Head Neck Surg 2021;73:378-82.  Back to cited text no. 4
Moein ST, Hashemian SM, Mansourafshar B, Khorram-Tousi A, Tabarsi P, Doty RL. Smell dysfunction: A biomarker for COVID-19. Int Forum Allergy Rhinol 2020;10:944-50.  Back to cited text no. 5
Jafari A, Alaee A, Ghods K. The etiologies and considerations of dysgeusia: A review of literature. J Oral Biosci 2021;63:319-26.  Back to cited text no. 6
Ghods K, Alaee A. Olfactory and taste disorders in patients suffering from COVID-19, a review of literature. J Dent (Shiraz) 2022;23:1-6.  Back to cited text no. 7
Del Carpio-Orantes L, García-Méndez S, Solís-Sánchez I, Arnulfo Perfecto-Arroyo M, Patricia Moreno-Aldama N, Salvador Sánchez-Díaz J. Neurological symptoms in patients with COVID-19 as manifestation of severity and prognosis, the case of anosmia and dysgeusia. J Neurol Sci 2021;429:119899.  Back to cited text no. 8
Bauer L, Laksono BM, de Vrij FM, Kushner SA, Harschnitz O, van Riel D. The neuroinvasiveness, neurotropism, and neurovirulence of SARS-CoV-2. Trends Neurosci 2022;45:358-68.  Back to cited text no. 9
Brann DH, Tsukahara T, Weinreb C, Lipovsek M, Van den Berge K, Gong B, 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:eabc5801.  Back to cited text no. 10
Bauer L, Rissmann M, Benavides FF, Leijten L, van Run P, Begeman L, et al. In vitro and in vivo differences in neurovirulence between D614G, delta and omicron BA.1 SARS-CoV-2 variants. Acta Neuropathol Commun 2022;10:124.  Back to cited text no. 11
Pastor-Sierra K, Penata-Taborda A, Coneo-Pretelt A, Jiménez-Vidal L, Arteaga-Arroyo G, Ricardo-Caldera D, et al. Factores ambientales en la transmisión del SARS-CoV-2/COVID 19: Panorama mundial y colombiano. Rev Univ Indian Santander Salud 2021;53:E301. Available from: http://www.scielo.org.co/scielo.php?script=sci_arttext&pid=S0121-08072021000100301&lng=en. [Last accessed on 2022 Sep 18].  Back to cited text no. 12
Bagheri SH, Asghari A, Farhadi M, Shamshiri AR, Kabir A, Kamrava SK, et al. Coincidence of COVID-19 epidemic and olfactory dysfunction outbreak in Iran. Med J Islam Repub Iran 2020;34:62.  Back to cited text no. 13


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
Host Factors
Agent Factors (S...
Environmental Fa...

 Article Access Statistics
    PDF Downloaded54    
    Comments [Add]    

Recommend this journal