SARS-CoV-2 Encephalitis versus Influenza Encephalitis: More Similarities than Differences.

Background: From time to time, physicians face challenging diagnostic and therapeutic issues concerning the acute management of children with viral encephalitis.

Objectives: The aim of this article is to provide an updated narrative review on the similarities and differences between SARS-CoV-2 and influenza encephalitis.

Methods: A PubMed search was performed with the function "Clinical Queries" using the key terms "SARS-CoV-2" OR "Influenza" AND "Encephalitis". The search strategy included metaanalyses, clinical trials, randomized controlled trials, reviews and observational studies. The search was restricted to the English literature and pediatric population. This article compares similarities and contrasts between SARS-CoV-2 and influenza-associated encephalitis.

Results: Encephalitis is an uncommon manifestation of both influenza and SARS-CoV-2. Both viruses are associated with fever and respiratory symptoms. However, SARS-CoV-2 patients may only have mild symptoms or be asymptomatic as silent carriers, rendering the disease spread difficult to control. Influenza patients usually have more severe symptomatology and are often bed bound for several days limiting its spread. Influenza is associated with seasonal and annual outbreaks, whereas SARS-CoV-2 has become endemic. Complications of encephalitis are rare in both viral infections but, when present, may carry serious morbidity and mortality. Many long-term sequelae of COVID- 19 infections (long COVID-19) have been described but not with influenza infections. Mortality associated with encephalitis appears higher with influenza than with SARS-CoV-2. Prophylaxis by immunization is available for both influenza and SARS-CoV-2. Specific efficacious antivirals are also available with oseltamivir for influenza and nirmatrelvir/ritonavir for SARS-CoV-2. Steroids are indicated with more severe SARS-CoV-2 but their role is not distinct in influenza disease.

Conclusion: Encephalitis is a rare complication of influenza and SARS-CoV-2 infections. Both carry significant morbidity and mortality. Efficacious vaccines for prophylaxis and antivirals for treatment are available for both viruses.