Altered taste in patients with COVID-19: The potential role of salivary glands

Frequency of Oral Lesions, Olfactory, and Gustatory Disorders and Xerostomia in Patients with COVID-19

COVID-19, a respiratory illness with a global impact on millions, has recently been linked to manifestations affecting various bodily systems, including the oral cavity. Studies highlight oral issues, like ulcers, blisters, and white patches, alongside olfactory and gustatory dysfunction, influencing an individual's quality of life. In this context, our study aimed to assess the frequency of oral lesions, olfactory and gustatory disorders, and xerostomia resulting from COVID-19. An observational study was conducted with 414 patients to evaluate the frequency of oral symptoms resulting from COVID-19. Patients were diagnosed with mild symptoms and evaluated through clinical examination of the oral cavity and a questionnaire to assess functional alterations. The findings showed that 139 out of 414 patients presented clinical manifestations, with oral lesions being the most prevalent (19.1%), followed by gustatory disorders (18.1%), xerostomia (14.2%), and olfactory dysfunction (14%). The most prevalent oral lesions were ulcerations (n = 51), candidiasis (n = 8), and erythema or red plaques (n = 7). Unfortunately, 50 (12.1%) patients died during this study. Therefore, oral lesions, olfactory and gustatory dysfunctions, and xerostomia are common symptoms associated with COVID-19.

Histological and molecular response of oral cavity tissues to Covid-19

The world is still dealing with Covid-19 waves, and maintaining good oral health has systemic effects on overall health. This review's objective is to identify the main oral manifestations of this illness, its effects on oral tissues at their histological bases, their molecular cell mechanisms, and the relationship issues between Covid-19 outcomes and oral health conditions. The main sources of the review are research articles published from 2000 to 2023. The main used terms in search were Covid-19 oral manifestations, Corona virus and Taste, or Olfaction, Covid and periodontitis, or Oral cavity. the angiotensin-converting enzyme II receptor (ACE2), which serves as a cellular entry point for viral entry into the cell to cause Covid-19 infection, is the target of corona virus attacks on human cells. The destruction of keratinocytes and oral fibroblasts, which is an indication of the virus's direct impact on oral tissues, results in inflammatory reactions in the salivary glands, tongue, and gingiva, which may explain both the loss of taste and the mouth ulceration. Additionally, there is a significant correlation between Covid-19 outcome and periodontitis. This results from the connection between hyperinflammation and poor oral hygiene.

A review on oral manifestations of COVID-19 disease

COVID-19, a multi-system-affecting disease presents with an extensive clinical spectrum, ranging from no symptoms at all to fatal lung involvement. Several orofacial manifestations have also been reported, among which dysgeusia is one of the earliest reported symptoms. Several other manifestations of extensive variety have also been reported by various authors worldwide since the outbreak of the disease. This comprehensive review dispenses a synopsis of the orofacial manifestations of COVID-19 along with a working classification, the knowledge of which is of utmost importance to medical and dental professionals for early detection and prevention of transmission of the disease.

The role of saliva in taste dysfunction among cancer patients: Mechanisms and potential treatment

Two of the highest prevalent symptoms reported by cancer patients are taste dysfunction (17.6-93%) and dry mouth/xerostomia (40.4-93%). While it has been hypothesized that reduced saliva may impair taste function, few studies investigate the co-occurrence of taste and dry mouth symptoms in cancer patients. This review provides a summary of the physiological relationship between saliva and taste, focusing on taste transduction mechanism, regulation of the taste sensitivity, and protection of taste receptor cells, including the impact of cancer treatments and malignancy on saliva function, salivary components, and the mechanisms in which it can negatively impact the taste function. Here, the authors present a scoping review of the recent literature reporting on the association between taste dysfunction and dry mouth in cancer patients, including reports of non-pharmaceutical liposomal agents or drugs taken to improve dry mouth symptoms that also assess taste dysfunction. Considering the complexities of cancer and cancer treatment, understanding the physiological relationship between saliva and taste function may provide important insight into identifying treatments for alleviating taste dysfunction and dry mouth symptoms. There are substantial research gaps given the limited studies assessing the co-occurrence of taste loss and dry mouth and inconsistencies in the assessment of these symptoms. Clinical studies examining taste dysfunction will provide a foundational groundwork that will help understand the relationship between taste and saliva. Considering the increased rates in survivorship and the significant negative impact of taste dysfunction on quality of life, more research is needed to reduce the suffering of cancer patients.

The Prevalence and Pathophysiology of Chemical Sense Disorder Caused by the Novel Coronavirus

Emerging viral infections are a ceaseless challenge and remain a global public health concern. The world has not yet come back to normal from the devastating effects of the highly contagious and pathogenic novel coronavirus, or Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Olfactory and taste dysfunction is common in patients infected by the novel coronavirus. In light of the emergence of different coronavirus variants, it is important to update the prevalence and pathophysiology of these side effects. In this review, articles published on the prevalence of olfactory and taste dysfunction from coronavirus disease (COVID-19) and their possible pathophysiologic mechanisms have been reviewed and reported. The modulatory role of different SARS-CoV-2 variants on the chemical senses is then described. The clinical relevance of chemical sense disorder and its long-term morbidity and management is also discussed.

COVID-19 Pandemic and Periodontal Practice: The Immunological, Clinical, and Economic Points of View

The recent global health problem, COVID-19, has had far-reaching impacts on lifestyles. Although many effective WHO-approved vaccines have been produced that have reduced the spread and severity of the disease, it appears to persist in humans for a long time and possibly forever as everyday it turns out to have new mutations. COVID-19 involves the lungs and other organs primarily through cytokine storms, which have been implicated in many other inflammatory disorders, including periodontal diseases. COVID-19 is in a close association with dental and periodontal practice from two respects: first, repeated mandatory lockdowns have reduced patient referrals to dentists and limited the dental and periodontal procedures to emergency treatments, whereas it is important to recognize the oral manifestations of COVID-19 as well as the influence of oral and periodontal disease on the severity of COVID-19. Second, dentistry is one of the high-risk professions in terms of close contact with unmasked individuals, necessitating redefining the principles of infection control. The pressures of the economic recession on patients as well as dentists add to the difficulty of resuming elective dental services. Therefore, this study is divided into two parts corresponding to what mentioned above: the first part examines the clinical and immunological associations between COVID-19 and periodontal and oral diseases, and the second part delineates the measures needed to control the disease transmission in dental clinics as well as the economic impact of the pandemic era on dental services.

Potential Contribution of Climate Conditions on COVID-19 Pandemic Transmission over West and North African Countries

COVID-19, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is a very contagious disease that has killed many people worldwide. According to data from the World Health Organization (WHO), the spread of the disease appears to be slower in Africa. Although several studies have been published on the relationship between meteorological parameters and COVID-19 transmission, the effects of climate conditions on COVID-19 remain largely unexplored and without consensus. However, the transmission of COVID-19 and sensitivity to climate conditions are also not fully understood in Africa. Here, using available epidemiological data over 275 days (i.e., from 1 March to 30 November 2020) taken from the European Center for Disease Prevention and Control of the European Union database and daily data of surface air temperature specific humidity and water vapor from the National Center for Environmental Prediction (NCEP), this paper investigates the potential contribution of climate conditions on COVID-19 transmission over 16 selected countries throughout three climatic regions of Africa (i.e., Sahel, Maghreb, and Gulf of Guinea). The results highlight statistically significant inverse correlations between COVID-19 cases and temperature over the Maghreb and the Gulf of Guinea regions. In contrast, positive correlations are found over the Sahel area, especially in the central part, including Niger and Mali. Correlations with specific humidity and water vapor parameters display significant and positive values over the Sahelian and the Gulf of Guinea countries and negative values over the Maghreb countries. Then, the COVID-19 pandemic transmission is influenced differently across the three climatic regions: (i) cold and dry environmental conditions over the Maghreb; (ii) warm and humid conditions over the Sahel; and (iii) cold and humid conditions over the Gulf of Guinea. In addition, for all three climatic regions, even though the climate impact has been found to be significant, its effect appears to display a secondary role based on the explanatory power variance compared to non-climatic factors assumed to be dominated by socio-economic factors and early strong public health measures.

Gustatory Function and Salivary Flow Rate in Healthy Adults

OBJECTIVES/HYPOTHESIS

In this study, we assessed gustatory function and whole-mouth saliva in healthy adults and investigated the association between gustatory function, salivary flow rate (SFR), and dry mouth.

STUDY DESIGN

Descriptive clinical study.

METHODS

We recruited 413 participants who reported a normal sense of smell-taste, comprising 206 females and 207 males with an age range of 19 to 80 years. Taste scores were obtained using whole-mouth tests to evaluate the gustatory function, SFR was assessed using the spitting method, and dry mouth was measured with the visual analog scale.

RESULTS

The total taste score (TTS) and SFR were significantly negatively correlated with age (r_taste  = -0.522, P < .001; r_SFR  = -0.200, P < .001): TTS was significantly lower after the age of 50 and SFR decreased significantly after age 65. Women exhibited a significantly higher TTS than men (P < .001). However, there was no effect of sex on SFR. Dry mouth was negatively correlated with TTS (r = -0.223, P < .01) and SFR (r = -0.218, P < .01). Multiple regression analysis showed the independent variables of age, sex, and dry mouth predicted 34% of the variation in taste, while the independent variables of age and dry mouth predicted 6.1% of the variation in whole-mouth saliva. TTS was not significantly correlated with the SFR in healthy adults (r = 0.094, P = .056).

CONCLUSIONS

Age and dry mouth are important factors affecting gustatory function and whole-mouth saliva, with women exhibiting better taste sensitivity than men. Furthermore, there is no direct correlation between SFR and gustatory function in healthy adults.

LEVEL OF EVIDENCE

3 Laryngoscope, 2021.

Oral Manifestations in Patients with COVID-19: A 6-Month Update

This is the first update of the previously published living systematic review that summarized evidence on the prevalence of oral signs and symptoms in patients with COVID-19. Hitherto, 183 studies were included, reporting data from 64,876 patients with COVID-19 worldwide. The overall prevalence of taste disorders was 38% (95% CI = 22% to 56%, I² = 98%). Hypogeusia, dysgeusia, and ageusia were also evaluated by a meta-analysis, and the pooled prevalence was 34% for hypogeusia, 33% for dysgeusia, and 26% for ageusia. Taste disorders were associated with a positive COVID-19 test (odds ratio [OR] = 7.54, 95% CI = 5.24 to 10.86, I² = 93%, P < 0.00001), showing high certainty of evidence. However, the association between taste disorders and mild/moderate severity of COVID-19 (OR = 1.63, 95% CI = 1.33 to 1.99, I² = 69%, P < 0.0001) and female patients with COVID-19 (OR = 1.77, 95% CI = 1.26 to 2.48, I² = 79%, P = 0.001) presented low certainty of evidence. Xerostomia was a new feature of this update, and the pooled data demonstrated a prevalence of 43% (95% CI = 36% to 50%, I² = 71%) in patients with COVID-19. Regarding oral mucosal lesions, the most common clinical pattern was aphthous like, followed by herpes-like lesions, candidiasis, glossitis/depapillation/geographic tongue, parotitis, and angular cheilitis. Oral lesions were more frequent in the tongue, lips, and palate, presenting miscellaneous clinical aspects that are more likely to represent coinfections. Therefore, the reanalysis of current evidence suggests the triad xerostomia, taste dysfunction, and oral mucosal lesions as common manifestations in patients with COVID-19. However, these outcomes are under discussion, and more studies will be necessary to confirm their association with direct SARS-CoV-2 infection in the oral cavity.

Oral Mucosa, Saliva, and COVID-19 Infection in Oral Health Care

The SARS-CoV-2 virus has shaken the globe with an ongoing pandemic of COVID-19 and has set challenges to every corner of the modern health care setting. The oral mucosa and saliva are high risk sites for higher viral loads and dental health care professionals are considered a high risk group. COVID-19-induced oral lesions and loss of taste and smell are common clinical complaints in the dental health care setting. The SARS-CoV-2 virus has been found to cause a wide range of non-specific oral mucosal lesions, but the specific diagnosis of these mucocutaneous lesions as COVID-19 lesions will facilitate the prevention of SARS-CoV-2 in dental health care settings and aid in proper patient management. The reported loss of taste and smell needs further investigation at the receptor level as it will give new insights into SARS-CoV-2 pathogenicity. The high yield of virus in the salivary secretion is a common finding in this infection and ongoing research is focusing on developing saliva as a rapid diagnostic fluid in COVID-19. In this review, we discuss the significance of oral mucosa, saliva and the relevance of the COVID-19 pandemic in dentistry.

Oral Symptoms Associated with COVID-19 and Their Pathogenic Mechanisms: A Literature Review

Since the worldwide spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, management of coronavirus disease 2019 (COVID-19) has been challenging for healthcare providers. The oral cavity is referred to as a target of SARS-CoV-2. The aim of this study was to review oral symptoms specific to COVID-19 patients from the point of view of symptom prevalence and pathogenesis and to speculate the pathogenic mechanisms underlying them. Scientific articles were retrieved by searching PubMed/MEDLINE, Google Scholar, medRxiv, and bioRxiv from 3 February 2020 to 31 December 2020, and they were reviewed by title, abstract, and text for relevance. The literature search indicated that COVID-19 patients frequently present with gustatory dysfunction, xerostomia, and oral mucosal lesions, while their prevalence is likely to vary by country, age, gender, and disease severity. Gustatory dysfunction and xerostomia appear at an early stage of SARS-CoV-2 infection and last relatively long. One of possible pathogenic mechanisms of both symptoms is attributed to the expression of viral cellular entry-relevant receptors in taste cells and salivary glands. Dental professionals who can first become aware of oral symptoms associated with COVID-19 will play a more active role in and make a greater contribution to diagnosis and prevention of COVID-19.

Prognosis of olfactory and gustatory dysfunctions in COVID-19 patients: A case series

Although most COVID‐19 patients feel their olfactory function returns to normal, the smell test demonstrates that a mild impairment of the olfactory function may have remained. Therefore, their olfactory function should be evaluated by a smell test.