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Close observation of the local transmission of influenza A(H1N1) viruses enabled an estimate of the length of time the virus was transmitted without a mutation. Of 4,448 isolates from 11 consecutive years, 237 isolates could be categorized into 57 strain groups with identical hemagglutinin genes, which were monitored for the entire duration of an epidemic season. In addition, 35 isolates with identical sequences were identified at the study site and in other countries within 147 days. Consequently, it can be postulated that once an influenza virus enters a temperate region, the strain rarely mutates before the end of the season.

The correlation of viral growth capability (n = 156) with the viral load in nasopharyngeal swabs (n = 76) was assessed. Epidemic influenza A/H1N1, A/H3N2, and B viruses showed a wide range of growth capability (104–1011 copies/mL) in Madin-Darby canine kidney cells. The growth was correlated with the nasopharyngeal viral load (r = 0.53). Six selected strains showed growth-dependent cell death (r = 0.96) in a growth kinetics assay. Epidemic influenza viruses exhibit a wide range of growth capability. Growth capability should be considered one of the key factors in disease prognosis.

To investigate the prevalence and background of children with medical complexity (CMC) and its secular trend in Japan.CMC were defined as patients under the age of 20 years requiring medical care and devices. The patients were enrolled using the national health insurance claims data of three hospitals and two rehabilitation centers in Tottori Prefecture. The study period was divided into three periods: Period 1, 2007-2010; Period 2, 2011-2014; and Period 3, 2015-2018.A total of 378 CMC were enrolled. The prevalence of CMC was 1.88 per 1000 population among subjects aged20 years in 2018, and it increased by approximately 1.9 times during the study period. The number of CMC who presented with severe motor and intellectual disabilities did not change from Period 1 to Period 3. Meanwhile, the number of CMC who had relatively preserved motor and intellectual abilities increased from 58 to 98. The proportion of CMC who required respiratory management and oxygen therapy increased by 1.3 and 1.8 times, respectively. By contrast, the proportion of CMC who need tube feeding decreased significantly between periods 1 and 3 (P 0.05).The prevalence of CMC increased almost twice during the 12-year study period; however, the increase in the number of patients with relatively preserved motor and intellectual abilities was pronounced. This study showed that the need for medical care and devices differed based on the underlying disorders and severity of CMC; therefore, individualized medical, welfare, and administrative services and education about the various types of CMC must be provided.

Background: Early predictors of status epilepticus (SE)-associated mortality and morbidity have not been systematically studied in children, considerably impeding the identification of patients at risk. Objectives: To determine reliable early predictors of SE-associated mortality and morbidity and identify the etiology of SE-associated sequelae in Japanese children. Methods: We conducted a prospective multicenter study of clinical findings and initial laboratory data acquired at SE onset, and assessed outcomes at the last follow-up examination. In-hospital death during the acute period and neurological sequelae were classified as poor outcomes. Results: Of the 201 children who experienced their first SE episode, 16 exhibited poor outcome that was most commonly associated with acute encephalopathy. Univariate analysis revealed that the following were associated with poor outcomes: young age (⩽24months); seizure duration >90min; seizure intractability (failure of the second anticonvulsive drug); biphasic seizures; abnormal blood glucose levels ( 250mg/dL); serum aspartate aminotransferase (AST) ⩾56U/L; and C-reactive protein (CRP) levels >2.00mg/dL. Multivariate analysis revealed that young age, seizure intractability, abnormal blood glucose levels, and elevated AST and CRP levels were statistically significant. Conclusions: Young age and seizure intractability were highly predictive of poor outcomes in pediatric SE. Moreover, abnormal blood glucose levels and elevated AST and CRP levels were predictors that might be closely associated with the etiology, especially acute encephalopathy and severe bacterial infection (sepsis and meningitis) in Japanese children.