ABSTRACT
This chapter discusses the basic biology of influenza viruses, the common signs of influenza, its epidemiology, and the basic pathophysiology of viral replication affecting the nervous system. The chapter focuses on the many different neurologic aspects of human influenza infection. The story begins with the multiple central nervous aspects of the 1918 influenza H1N1 pandemic including encephalitis lethargica, and postencephalitic parkinsonism. Next, is the role of influenza in Reye’s syndrome that includes the experimental mouse model of Reye’s syndrome. The third part discusses the role of a few influenza vaccines’ association with Guillain–Barre syndrome, a monophasic rapidly evolving motor polyradiculoneuropathy, and the role other strains of influenza in childhood febrile seizures, an encephalopathy syndrome, and acute necrotizing encephalitis. The final part discusses the new highly pathogenic avian influenzas (H5N1 and H7N9) discovered in China and other parts of Asia in 1997 in circulating in wild waterfowl that occasionally cause severe disease when humans come in close contact to the infected fowl. While influenza virus primarily causes a respiratory infection, influenza strains frequently mutate in nature causing outbreaks of seizures, encephalopathy, focal areas of cerebral necrosis, Parkinsonism, myalgias, myositis, and hepatic dysfunction producing an acute noninflammatory encephalopathy. To date, we cannot predict or prevent the next influenza viral mutation that will cause neurologic complications as the new mutations are usually not preventable by current influenza vaccines.
