Encephalitis and Encephalopathy Associated with an Influenza Epidemic in Japan

Abstract

During the winter of 1998-1999, there was an outbreak of encephalitis/encephalopathy in Japan that appeared to be associated with influenza. We conducted a national survey of the prevalence and clinical features of disease and the associated outcomes and prognostic factors related to this outbreak. A total of 202 cases were analyzed, of which 148 were diagnosed as influenza-associated encephalitis/encephalopathy on the basis of virologic analysis. Of the 148 cases studied, 130 (87.8%) were type A influenza and 17 were type B. Encephalitis/encephalopathy developed mainly in children age <5 years, either on the day that influenza signs appeared or on the next day. The major signs included altered consciousness or loss of consciousness, convulsions, cough, and vomiting. In many patients, multiple-organ failure developed, and rates of mortality (31.8%) and disability (27.7%) were high. Thrombocytopenia and severely elevated transaminase levels were factors associated with a poor prognosis. Thus, influenza-associated encephalitis/encephalopathy progressed rapidly and was associated with poor outcomes.

Shedding of live vaccine virus, comparative safety, and influenza-specific antibody responses after administration of live attenuated and inactivated trivalent influenza vaccines to HIV-infected children

“…Author manuscript; available in PMC 2009 August 5. 3 [2] 3 [1] 20 [7] 12 [5] Total Subjects All adverse events were counted per subject. 2 Examples of adverse event categories are: abdominal = diarrhea, emesis, pain; constitutional = fever, chills, headache, malaise, fatigue, anorexia; ear or eye = conjunctivitis, ear pain, otitis media; injection site = tenderness, erythema, swelling; nasopharyngeal = discharge, congestion, sore throat; other = lymphadenitis, epistaxis, other viral illnesses; pulmonary = cough, chest pain, pneumonia, asthma; skin = rash, folliculitis, boil, cellulitis.…”

“…The resulting illness usually causes mild or moderately severe upper respiratory and systemic symptoms, but more significant tracheobronchial involvement is common. Rarely central nervous system and other complications accompany influenza infection (1,2), but the most common complications are bacterial superinfection, such as otitis media, sinusitis, and pneumonia (3)(4)(5)(6)(7). Influenza has an even greater potential to cause bacterial complications in some HIV-infected children, and is likely to complicate their routine care during epidemic periods (8).…”

Neurologic Complications Associated With Influenza A in Children During the 2003–2004 Influenza Season in Houston, Texas

“…12 With the advent of serologic testing, confirmed cases of influenza virus infection (A and B) have been associated with seizures (febrile and nonfebrile), 6,13,14 alterations in mental status ranging from confusion and lethargy to coma, 7,8,15,16 acute inflammatory demyelinating polyneuropathy (Guillain-Barre syndrome), 17,18 acute disseminated encephalomyelitis, 17 transverse myelitis, 17 abnormal movements, 19 acute psychosis, 20 frontal lobe syndromes, 21 mutism, 9,10 and visual hallucinations. 22 These complications have been reported sporadically in the literature over the past 60 years.…”

“…Recently, however, hundreds of cases of encephalopathy associated with influenza have been reported in Japan. 6,21,[23][24][25] In these series, a subset of patients (both children and adults) developed a newly described entity termed "acute necrotizing encephalopathy" (ANE). 14,23,26,27 Many patients with this syndrome present with high fever, seizures, and alterations in mental status that rapidly progress to coma.…”

“…Most recently, epidemic influenza in Japan in the late 1990s was associated with hundreds of cases of encephalopathy among children. 5,6 Although the majority of the patients had relatively minor symptoms, a small but significant number experienced serious complications, resulting in neurologic sequelae and even death. Small numbers of children with neurologic complications have been reported sporadically in Europe and Canada, whereas reports from the United States in the past 60 years have been exceedingly rare.…”