This cohort study aims to investigate the long-standing chemosensory disorders and oral manifestation after recovery of the COVID-19 illness. A correlation between the long-standing symptoms and the COVID-19 severity grade will be very important to understand and clarify the aetiology of these symptoms.

This prospective cohort study aims to investigate the long-standing chemosensory disorders and oral manifestation after recovery of the COVID-19 illness. A correlation between the long-standing symptoms and the COVID-19 severity grade will be very important to understand and clarify the aetiology of these symptoms.

Study objectives:

1. To describe the frequency and severity of oral signs and chemosensory disorders that persist after the recovery of COVID-19 and to examine whether "taste disorders" can be discriminated into an- or hypogeusia and an- or hyposmia.
2. To report any correlation between the severity grade of COVID-19 and the resulting standing symptoms.
3. To describe the oral microbiome after infection with COVID-19 and to describe possible changes in comparison to normal healthy individuals.

Clinical and -if indicated- radiological examination to assess the long-term oral and chemosensory impairment and complaints of COVID-19 patients after their recovery shall be performed in an interdisciplinary setting of Maxillofacial Surgery, ENT and Medical Microbiology.

The study subjects will be divided into three groups according to the severity grade of illness: non-hospitalized, hospitalized, and intensive care patients. All adult COVID-19 recovery patients (exceeding the age of 18) will be included in the study. The time between illness and study recruitment shall be at least 3 months. Exclusion criteria are psychiatric or neurological diseases, previous trauma, surgery or radiotherapy in the oral or nasal cavities, pre-existing taste or smell dysfunctions or chronic rhinosinusitis.

The study variables include age, sex, co-morbidities, possible causes of exclusion from the study. The oral health assessment will be performed by examination of: periodontal status, assessment of oral lesions, a radiological examination by using panoramic x-ray if clinically indicated, photo documentation, objective evaluation of the olfactory and gustatory functions with psychophysical tests. The gustatory and olfactory function will be tested by using the combined Burghart Screening 12 test containing smelling sticks and taste strips (Fa. MediSense, Groningen, Netherlands). Evaluation of taste and smell is performed by offering the sticks/strips and demand a forced multiple choice.

Inclusion Criteria:

• All adult COVID-19 recovery patients (exceeding the age of 18) will be included in the study. The time between illness and study recruitment shall be at least 3 months.

Exclusion Criteria:

• Exclusion criteria are psychiatric or neurological diseases, previous trauma, surgery or radiotherapy in the oral or nasal cavities, pre-existing taste or smell dysfunctions or chronic rhinosinusitis.

Study subjects will be divided into three groups according to the severity grade of illness: non-hospitalized, hospitalized, and intensive care patients.