**2. Neurocognitive impairment in the previous coronavirus outbreaks**

Two major coronavirus outbreaks were reported before the SARS-CoV-2 infection. These outbreaks were acute respiratory distress syndrome (ARDS) associated with SARS-CoV and Middle East respiratory Syndrome (MERS) associated with MERS-CoV virus [6, 16]. Neurocognitive disorders during the COVID-19 pandemic process have often been compared with these outbreaks. It has been reported that neurocognitive impairment is dominant in the COVID-19 process. These results were explained by the psychosocial effect of the disease and social isolation [12]. However, neurocognitive impairment is not only associated with psychosocial processes. Because the induced systemic inflammatory process contributes to neurocognitive dysfunction [14]. In a study of MERS-CoV patients, confusion was indicated to be associated with magnetic resonance imaging (MRI) results [17]. It was reported that approximately 25.7% of the patients had confusion [18].

Confusion, neurocognitive and neuropsychiatric symptoms are not only present in coronavirus infection. Inattention, memory and learning defects have been reported in human immunodeficiency virus (HIV) and Zika virus (ZIKV) diseases [19, 20]. Influenza virus may also cause cognitive dysfunction. The clinical presentation of the disease may progress from mild cognitive impairment to seizure and/or severe encephalopathy [21]. Influenza-associated neurological clinical manifestation is not common compared to coronavirus. In a national study conducted in Malaysia, the rate of neurological manifestation was detected as 8.3%. The hospitalization rate is higher in this patient group. However, long-term cognitive deficits are rare in patients with influenza [21, 22].
