Estimation of the Basic Reproduction Number of Novel Influenza A (H1N1) pdm09 in Elementary Schools Using the SIR Model.

BACKGROUND: The novel influenza A (H1N1) pdm09 (A/H1N1pdm) pandemic of 2009-2010 had a great impact on society. OBJECTIVE: We analyzed data from the absentee survey, conducted in elementary schools of Oita City, to evaluate the A/H1N1pdm pandemic and to estimate the basic reproductive number (R0 ) of this novel strain. METHOD: We summarized the overall absentee data and calculated the cumulative infection rate. Then, we classified the data into 3 groups according to school size: small (<300 students), medium (300-600 students), and large (>600 students). Last, we estimated the R0 value by using the Susceptible-Infected-Recovered (SIR) mathematical model. RESULTS: Data from 60 schools and 27,403 students were analyzed. The overall cumulative infection rate was 44.4%. There were no significant differences among the grades, but the cumulative infection rate increased as the school size increased, being 37.7%, 44.4%, and 46.6% in the small, medium, and large school groups, respectively. The optimal R0 value was 1.33, comparable with that previously reported. The data from the absentee survey were reliable, with no missing values. Hence, the R0 derived from the SIR model closely reflected the observed R0 . The findings support previous reports that school children are most susceptible to A/H1N1pdm virus infection and suggest that the scale of an outbreak is associated with the size of the school. CONCLUSION: Our results provide further information about the A/H1N1pdm pandemic. We propose that an absentee survey should be implemented in the early stages of an epidemic, to prevent a pandemic.

Ultrasonic findings of fetal axillary lymphangioma with intralesional hemorrhage.

We report a case of an axillary lymphangioma in a fetus delivered at 30 weeks' gestation with suspected intralesional hemorrhage based on the ultrasonic findings. In the ultrasonic examination at 15 weeks' gestation, the fetus was found to have a multilocular mass spreading from the axilla to the chest wall, which was diagnosed as an axillary lymphangioma. Chromosome analysis by amniocentesis showed a normal karyotype, and no other malformations were observed. At 29 weeks, the mass had increased in size, and color Doppler ultrasound examination revealed that the middle cerebral artery peak systolic velocity (MCA-PSV) reached 80.2 cm/s [1.86 MoM (multiples of the median)]. Intralesional bleeding was suspected because of the multiple images of hemorrhage in which sites of blood spouting in a pulsatile fashion were detected within the mass. Cordocentesis at 30 weeks revealed that fetal hemoglobin concentration was 5.1 g/dL. An emergency Cesarean section was performed. A female weighing 2810 g, including the mass, was delivered, and the blood hemoglobin level was 5.9 g/dL at birth. Blood transfusion, fine-needle aspiration of the fluid in the mass, intralesional injection of OK-432, and partial excision of the lymphangioma were performed after birth. Ultrasonic examination proved useful in the diagnosis of intralesional bleeding in this lymphangioma.

Substantial Impact of School Closure on the Transmission Dynamics during the Pandemic Flu H1N1-2009 in Oita, Japan.

BACKGROUND: School closure is considered as an effective measure to prevent pandemic influenza. Although Japan has implemented many class, grade, and whole school closures during the early stage of the pandemic 2009, the effectiveness of such a school closure has not been analysed appropriately. In addition, analysis based on evidence or data from a large population has yet to be performed. We evaluated the preventive effect of school closure against the pandemic (H1N1) 2009 and examined efficient strategies of reactive school closure. MATERIALS AND METHODS: Data included daily reports of reactive school closures and the number of infected students in the pandemic in Oita City, Japan. We used a regression model that incorporated a time delay to analyse the daily data of school closure based on a time continuous susceptible-exposed-infected-removed model of infectious disease spread. The delay was due to the time-lag from transmission to case reporting. We simulated the number of students infected daily with and without school closure and evaluated the effectiveness. RESULTS: The model with a 3-day delay from transmission to reporting yielded the best fit using R2 (the coefficient of determination). This result suggests that the recommended period of school closure is more than 4 days. Moreover, the effect of school closure in the simulation of school closure showed the following: the number of infected students decreased by about 24% at its peak, and the number of cumulative infected students decreased by about 8.0%. CONCLUSIONS: School closure was an effective intervention for mitigating the spread of influenza and should be implemented for more than 4 days. School closure has a remarkable impact on decreasing the number of infected students at the peak, but it does not substantially decrease the total number of infected students.

Severe impaction of the primary mandibular second molar accompanied by displacement of the permanent second premolar.

Tooth impaction is defined as any tooth that fails to erupt into a normal functional position and remains unerupted beyond the time at which it should normally erupt. Reports of impaction and eruption failure in primary teeth are relatively rare compared to permanent teeth. We report 2 rare cases where the second premolar was located on the occlusal side of the impacted mandibular second primary molar. In the first case, the succedaneous permanent tooth erupted after extraction of the primary tooth, fenestration, and traction. In the second case, the succedaneous permanent tooth erupted without fenestration or traction. Although the etiology of the tooth displacement was unknown in both cases, inhibition of the eruptive movement of the primary molar may have been associated with displacement of the succedaneous permanent premolar.

Clinical and radiographic findings and usefulness of computed tomographic assessment in two children with regional odontodysplasia.

Regional odontodysplasia is a rare, severe, and nonhereditary developmental disorder in tooth formation and involves epithelial and mesenchymal-derived dental tissue. On radiographs, affected teeth have an abnormal morphology, a hypoplastic crown, and only a faint outline of hard tissue, a condition termed "ghost teeth." We report clinical and radiographic findings from two children with regional odontodysplasia. Using computed tomography (CT), we calculated attenuation coefficients (i.e., Hounsfield units) for affected teeth and assessed the condition of dental follicles. To measure density, regions of interest were delimited and CT values were calculated. In our two patients, the CT values for enamel were lower in affected teeth than in sound teeth, while CT values for dentin were similar for affected and sound teeth. The average CT value for dental follicles in affected teeth was about 65 to 120, which suggests that dense fibrous connective tissues or hard tissue-like structures might be present in dental follicles. Analysis of CT values may be quite useful in the diagnosis and treatment of regional odontodysplasia.

[Emergency cesarean section].

There are abundant cases of obstetric emergencies demanding prompt intervention. Emergency cesarean sections are classified into stable, urgent and immediate surgeries, although there is significant overlap between three groups. Stable emergency cesarean sections are performed in patients with stable maternal and fetal physiology, but who need surgery before unstability occurs. Urgent cesarean sections refer to situations in which maternal and/or fetal physiology is unstable, whereas the immediate cesarean section is used for life-threatening condition such as sustained fetal bradycardia, maternal cardiopulmonary arrest. In most cases the key to proper management is the prompt communication between obstetricians and anesthesiologists. Anesthesiologists must have a clear understanding of certain obstetric emergencies. In the event of sustained fetal bradycardia caused by placental abruption, cord prolapse, uterine rupture etc, delivery by immediate cesarean section within 25 minutes improve long-term neonatal neurologic outcome. Although cardiopulmonary arrest in pregnancy is very uncommon, peripartum cesarean section should be considered within 5 minutes not only for maternal resuscitation but for neonatal survival. Only a well-coordinated teamwork of all involved specialities will guarantee optimal prognosis of mother and fetus.

Relationship between congenitally missing lower third molars and late formation of tooth germs.

In this investigation, we used longitudinal panoramic radiographs from 96 subjects (47 boys, 49 girls) who did not have any congenital disease. The subjects were selected based on their age at the initial radiograph and the number and frequency of radiographs. Lower left premolars and second molars were used as parameters to identify factors that influence the age of formation of the third molar. We classified teeth into eight formation stages according to the method of Demirjian. The age at the beginning of formation of the lower third molar was determined with a regression equation of longitudinal data. The highest correlation existed between the age at the beginning of formation of the third molar and the formation stage of the second molar. We conclude that late formation of tooth germs is one of the factors that leads to the congenital absence of lower third molars. Furthermore, we assume that when the tooth germ of the lower third molar has not appeared at stage 7 of formation of the second molar, the probability of the third molar being missing is 100%.