Neurological Involvements of SARS-CoV2 Infection.

COVID-19 is a pandemic viral infection caused by a novel coronavirus, SARS-CoV2, which is a global concern of the twenty-first century for its rapid spreading in a short period. Apart from its known acute respiratory involvements, the CNS manifestations of COVID-19 are common. These neurological symptoms are diverse and could range from mild nonspecific or specific symptoms such as the loss of various sensory perceptions, the worrying autoimmune Guillain-Barré syndrome, to the life-threatening acute disseminated encephalomyelitis, and the CNS-mediated respiratory distress. An autopsy report documented the presence of SARS-CoV2 in brain tissues of a COVID-19 patient. However, there is no definite conclusion on the mechanisms of SARS-CoV2 neuroinvasion. These proposed mechanisms include the direct viral invasion, the systemic blood circulation, or the distribution of infected immune cells. Concerning these different neuropathophysiologies, COVID-19 patients who are presenting with either the early-onset, multiple, and severe CNS symptoms or rapid respiratory deterioration should be suspected for the direct viral neuroinvasion, and appropriate management options should be considered. This article reviews the neurological manifestations, the proposed neuroinvasive mechanisms, and the potential neurological sequelae of SARS-CoV2.

Development of Rift valley fever encephalitis in rats is mediated by early infection of olfactory epithelium and neuroinvasion across the cribriform plate.

The zoonotic emerging Rift Valley fever virus (RVFV) causes sporadic disease in livestock and humans throughout Africa and the Saudi Arabian peninsula. Infection of people with RVFV can occur through mosquito bite or mucosal exposure during butchering or milking of infected livestock. Disease typically presents as a self-limiting fever; however, in rare cases, hepatitis, encephalitis and ocular disease may occur. Recent studies have illuminated the neuropathogenic mechanisms of RVFV in a rat aerosol infection model. Neurological disease in rats is characterized by breakdown of the blood-brain barrier late in infection, infiltration of leukocytes to the central nervous system (CNS) and massive viral replication in the brain. However, the route of RVFV entry into the CNS after inhalational exposure remains unknown. Here, we visualized the entire nasal olfactory route from snout to brain after RVFV infection using RNA in situ hybridization and immunofluorescence microscopy. We found widespread RVFV-infected cells within the olfactory epithelium, across the cribriform plate, and in the glomerular region of the olfactory bulb within 2 days of infection. These results indicate that the olfactory tract is a major route of infection of the brain after inhalational exposure. A better understanding of potential neuroinvasion pathways can support the design of more effective therapeutic regiments for the treatment of neurological disease caused by RVFV.

Bacterial pathogens in the nasopharynx, nasal cavity, and osteomeatal complex during wellness and viral infection.

BACKGROUND: Viral sinusitis can precede acute bacterial sinusitis, but the influence of viral infection on bacterial colonization is unclear. The objective of this study was to evaluate the presence of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the osteomeatal complex (OMC), nasal cavity, and nasopharynx in adults during wellness and viral upper respiratory illness (URI). METHODS: Subjects were recruited for the study during wellness and at the time of acute viral rhinosinusitis. Swab cultures were obtained from the OMC, nasal cavity, and the nasopharynx. Swab eluates were inoculated on selective agars to detect S. pneumoniae, H. influenzae, and M. catarrhalis. RESULTS: The study included 237 subjects, 100 adults with URI and 137 well adults. Positive culture results were found for any site in 70% (n = 70) of ill subjects and 64% (n = 88) of well subjects (p = 0.393). Of the 91 OMC cultures, positive cultures were over five times more likely to be found in ill subjects than in well subjects (31% versus 8%; p = 0.010). The nasal cavity cultures were positively statistically significant more often in ill subjects versus well subjects (39% versus 25%; p = 0.022). The overall nasopharyngeal cultures did not show a statistically significant difference (65% versus 60%; odds ratio, 1.2; p = 0.461). S. pneumoniae was positively cultured in at least one site in 15% of ill subjects and 31% of well subjects (p = 0.006). H. influenzae was positively cultured in at least one site in 45% of ill subjects and 31% of well subjects (p = 0.027). M. catarrhalis was positively cultured in at least one site in 42% of ill subjects and 27% of well subjects (p = 0.018). CONCLUSION: This study defines the carriage rates of the three most common bacterial pathogens for acute sinusitis in the nasopharynx, nasal cavity, and OMC during illness and in the healthy state.

Effects of viral and bacterial infection on nasal and sinus mucosa.

There is still controversy over the role of viruses and bacteria in rhinologic infections, especially in sinusitis. Until recently it was not fully known whether the sinuses do in fact take part in the infectious process of a common cold (viral rhinitis). CT scans show that in the vast majority of otherwise healthy volunteers with a common cold, and without a previous history of recurrent or chronic sinusitis, the sinuses are involved; there was, however, in these individuals no typical symptomatology of acute sinusitis. A viral rhinitis alone does not seem to be able to elicit a "clinical" acute otitis. Bacteria determine the clinical picture and outcome of sinusitis. There is not much controversy about the role of bacteria in acute sinusitis, S. pneumoniae, H. influenzae, and M. catarrhalis being the most frequently involved. Much more conflicting reports are published about the normal flora of the sinuses, the role of anaerobes and the microbiology of chronic sinusitis. In this paper the mechanisms of viral and bacterial infection of the nasal and sinusal mucosa are described and the results of microbiological studies in sinusitis reported by other authors and our own group are discussed. It is postulated that, although bacteria are very important in acute sinusitis, their role in chronic sinusitis is minimal, the bacteria being opportunistic colonisers.