CPAP Treatment in Pediatric Obstructive Sleep Apnea / 수면정신생리

Adenotonsillar hypertrophy is the most common cause of pediatric obstructive sleep apnea (OSA) in children, and therefore, adenotonsillectomy is the first-line therapy in most pediatric patients. In cases of residual OSA after adenotonsillectomy, and in cases where surgical intervention is not feasible, positive airway pressure (PAP) therapy is often employed. Those conditions include obesity, craniofacial malformation, Down syndrome, and neuromuscular disorders. In this article, continuous positive airway pressure (CPAP) preparation, titrations, barriers to effective CPAP therapy, monitoring, and adherence to CPAP in children will be described.

Prediction of COVID-19-related Mortality and 30-Day and 60-Day Survival Probabilities Using a Nomogram

Background@#Prediction of mortality in patients with coronavirus disease 2019 (COVID-19) is a key to improving the clinical outcomes, considering that the COVID-19 pandemic has led to the collapse of healthcare systems in many regions worldwide. This study aimed to identify the factors associated with COVID-19 mortality and to develop a nomogram for predicting mortality using clinical parameters and underlying diseases. @*Methods@#This study was performed in 5,626 patients with confirmed COVID-19 between February 1 and April 30, 2020 in South Korea. A Cox proportional hazards model and logistic regression model were used to construct a nomogram for predicting 30-day and 60-day survival probabilities and overall mortality, respectively in the train set. Calibration and discrimination were performed to validate the nomograms in the test set. @*Results@#Age ≥ 70 years, male, presence of fever and dyspnea at the time of COVID-19 diagnosis, and diabetes mellitus, cancer, or dementia as underling diseases were significantly related to 30-day and 60-day survival and mortality in COVID-19 patients. The nomogram showed good calibration for survival probabilities and mortality. In the train set, the areas under the curve (AUCs) for 30-day and 60-day survival was 0.914 and 0.954, respectively; the AUC for mortality of 0.959. In the test set, AUCs for 30-day and 60-day survival was 0.876 and 0.660, respectively, and that for mortality was 0.926. The online calculators can be found at https://koreastat.shinyapps.io/RiskofCOVID19/. @*Conclusion@#The prediction model could accurately predict COVID-19-related mortality; thus, it would be helpful for identifying the risk of mortality and establishing medical policies during the pandemic to improve the clinical outcomes.

Prediction of COVID-19-related Mortality and 30-Day and 60-Day Survival Probabilities Using a Nomogram

Background@#Prediction of mortality in patients with coronavirus disease 2019 (COVID-19) is a key to improving the clinical outcomes, considering that the COVID-19 pandemic has led to the collapse of healthcare systems in many regions worldwide. This study aimed to identify the factors associated with COVID-19 mortality and to develop a nomogram for predicting mortality using clinical parameters and underlying diseases. @*Methods@#This study was performed in 5,626 patients with confirmed COVID-19 between February 1 and April 30, 2020 in South Korea. A Cox proportional hazards model and logistic regression model were used to construct a nomogram for predicting 30-day and 60-day survival probabilities and overall mortality, respectively in the train set. Calibration and discrimination were performed to validate the nomograms in the test set. @*Results@#Age ≥ 70 years, male, presence of fever and dyspnea at the time of COVID-19 diagnosis, and diabetes mellitus, cancer, or dementia as underling diseases were significantly related to 30-day and 60-day survival and mortality in COVID-19 patients. The nomogram showed good calibration for survival probabilities and mortality. In the train set, the areas under the curve (AUCs) for 30-day and 60-day survival was 0.914 and 0.954, respectively; the AUC for mortality of 0.959. In the test set, AUCs for 30-day and 60-day survival was 0.876 and 0.660, respectively, and that for mortality was 0.926. The online calculators can be found at https://koreastat.shinyapps.io/RiskofCOVID19/. @*Conclusion@#The prediction model could accurately predict COVID-19-related mortality; thus, it would be helpful for identifying the risk of mortality and establishing medical policies during the pandemic to improve the clinical outcomes.

Pediatric sleep questionnaires for screening of obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is the most severe form of obstructive sleep-disordered breathing. It can produce cardiovascular problems, growth retardation, cognitive deficits, and behavioral problems such as attention deficit/hyperactivity symptoms in children. The diagnostic gold standard for OSAS is overnight polysomnography, but it is expensive, time-consuming, and labor intensive, and is conducted by specialized centers which have trained personnel. Therefore, sleep questionnaires as screening tools for OSAS was developed. The benefits of sleep questionnaires are easy/quick application and low cost. The objective of this review is to describe several available pediatric sleep questionnaires which are helpful in screening OSAS.

Comparison of Split versus Subunit Seasonal Influenza Vaccine in Korean Children over 3 to under 18 Years of Age

PURPOSE: This study was conducted to compare immunogenicities and reactogenicities of the trivalent inactivated subunit influenza vaccine and split influenza vaccine in Korean children and adolescents.METHODS: In total, 202 healthy children aged 36 months to <18 years were enrolled at six hospitals in Korea from October to December 2008. The subjects were vaccinated with either the split or subunit influenza vaccine. The hemagglutinin inhibition antibody titers against the H1N1, H3N2, and B virus strains were measured, and the seroconversion rates, seroprotection rates, and geometric mean titers were calculated. All subjects were observed for local and systemic reactions.RESULTS: Both the split and subunit vaccine groups had similar seroprotection rates against all strains (95.9%, 94.9%, 96.9% vs. 96.0%, 90.9%, and 87.9%). In children aged 36 to <72 months, the seroprotection rates were similar between the two vaccine groups. In children aged 72 months to <18 years, both vaccines showed high seroprotection rates against the H1N1, H3N2, and B strain (98.4%, 98.4%, 98.4% vs. 97.0%, 95.5%, and 91.0%), but showed relatively low seroconversion rates (39.1%, 73.4%, 35.9% vs. 34.3%, 55.2%, and 38.8%). There were more local and systemic reactions in the split vaccine group than in the subunit vaccine group; however, no serious adverse reactions were observed in both groups.CONCLUSIONS: Both the split and subunit vaccines showed acceptable immunogenicity in all age groups. There were no serious adverse events with both vaccines.

Clinical Features and Laboratory Findings in Children Diagnosed with Benign Acute Childhood Myositis (BACM) / 대한소아신경학회지

PURPOSE: This study was performed to review the relationship between the clinical features and laboratory findings of patients suspected of benign acute childhood myositis (BACM) in children and adolescents with bilateral calf pain and gait disturbances. METHODS: From January 1, 2010 to December 31, 2016, the clinical and laboratory findings of patients who visited Dongguk University Ilsan Hospital with the sudden onset fever and muscle pain were retrospectively examined. RESULTS: The total number of patients was 29 (21 males and 8 females), and their mean age was 5.5 years. The mean duration of fever was 4.2 days. The mean duration from the onset of fever to show the symptom was 3.2 days. The mean recovery period from myositis was 2.4 days. The mean duration of hospitalization was 2.2 days. Fever and bilateral calf pain were the most common symptoms; however, cough, rhinorrhea, sore throat, headache, and abdominal pain were also observed. The causative agent of BACM was influenza B infection in 23 (79.3%) of the cases. Creatinine phosphokinase (CPK), myoglobin, aspartate aminotransferase (AST), and alanine transaminase (ALT) values were higher in the shorter duration of fever and were statistically significant. The following values were noted: CPK (r=−0.472), myoglobin (r=−0.472), AST (r=−0.443), and ALT (r=−0.459). The longer the pain period, the lower the white blood cell (WBC) count (r=−0.655). CONCLUSION: BACM is mostly associated with the influenza B virus. Time to onset of symptoms after fever and WBC levels are related to muscle enzyme levels and duration of symptoms in BACM.

Ileal Perforation with Norovirus Gastroenteritis in a 3-Month-Old Infant / 대한소아소화기영양학회지

Noroviruses have been recognized as the leading cause of epidemic and sporadic gastroenteritis since the advent of molecular diagnostic technique. They have been documented in 5-31% of pediatric patients hospitalized with gastroenteritis. Although norovirus gastroenteritis is typically mild and self-limited, it causes severe, but sometimes fatal, conditions in the vulnerable population such as immunocompromised patients, young children, and the elderly. Bowel perforation due to norovirus infection is rare. We report a case of small bowel perforation with norovirus gastroenteritis in the infant with Down syndrome during the hospitalization with pneumonia. Severe dehydration may cause bowel ischemia and could have triggered bowel perforation in this case. Physicians should be alert to the potential surgical complications followed by severe acute diarrhea, especially in high risk groups.

Differences in Clinical Manifestations and Treatment Responses in Influenza Type A and B in a Single Hospital during 2013 to 2015

PURPOSE: We suspect there is a difference in the clinical manifestations and treatment response to antiviral drugs for influenza A and B. This study was conducted to investigate this difference. METHODS: We collected information on pediatric patients, infected with the influenza virus, admitted to Dongguk University Ilsan Hospital from October 2013 to May 2015. We investigated the clinical manifestations of influenza and differences in treatment response to oseltamivir treatment for the two types of influenza. RESULTS: A total of 138 patients were included. The mean age was 3.5±4.0 years. When comparing the diseases associated with influenza A and B, croup (19.2% vs. 1.7%, P=0.001) was more common with influenza A infection. Myositis (0% vs. 6.7%, P=0.021) and gastroenteritis (29.5% vs. 46.7%, P=0.038) were more common with influenza B infection. When comparing the total fever duration from the start of oseltamivir administration, patients treated with oseltamivir within 2 days of fever had the shortest duration. Among the patients treated with oseltamivir, the duration of fever, after the start of oseltamivir treatment, for was shorter for influenza A infection than for influenza B infection (16.0±19.1 hours vs. 28.9±27.9 hours, P=0.006). CONCLUSIONS: There appear to be differences in the accompanying diseases and antiviral medication responses between the two types of influenza. It is important to administer oseltamivir within 2 days of fever.

Clinical Manifestations of Group A Streptococcal Pharyngitis and Comparison of Usefulness of Two Rapid Streptococcal Antigen Tests

BACKGROUND: Throat culture is the golden standard for diagnosis of group A streptococcal (GAS) pharyngitis. However, because it is a time-consuming procedure, antibiotics are often empirically administrated. Rapid antigen tests (RATs) can detect bacterial infections within 15 minutes, thus helping to reduce unnecessary administration of antibiotics. METHODS: In total, 108 patients, between 3 and 17 yr of age, who visited our hospital from August 2011 to July 2012, were tested for suspected acute pharyngitis with two RATs––SD Bioline Strep A (SD, Korea) and BinaxNOW Strep A (Binax, Inc., USA)––as well as throat culture. We compared the sensitivity, specificity, and consistency of the two RATs and assessed the clinical manifestations of GAS pharyngitis. RESULTS: Of the 108 patients, 15 were confirmed to have GAS pharyngitis by throat culture. The SD test showed a sensitivity of 93.3% and a specificity of 97.8%; the positive and negative predictive values were 87.5% and 98.9%, respectively. The Binax test showed a sensitivity of 86.7% and a specificity of 100%; the positive and negative predictive values were 100% and 97.9%, respectively. The Kappa values for conformity degree were high, 0.887 and 0.918 in the SD and the Binax tests, respectively (P=0.00). Clinical manifestation assessment of GAS pharyngitis indicated that scarlatiniform rash and strawberry tongue were significantly associated signs (P<0.05). CONCLUSIONS: GAS pharyngitis diagnosis based on clinical manifestations alone has practical limitations. The two RATs are useful as substitutes for throat culture and their frequent use in clinical settings is advisable.

Clinical Practice Guideline of Acute Respiratory Distress Syndrome / 대한구급학회지

There is no well-stated practical guideline for mechanically ventilated patients with or without acute respiratory distress syndrome (ARDS). We generate strong (1) and weak (2) grade of recommendations based on high (A), moderate (B) and low (C) grade in the quality of evidence. In patients with ARDS, we recommend low tidal volume ventilation (1A) and prone position if it is not contraindicated (1B) to reduce their mortality. However, we did not support high-frequency oscillatory ventilation (1B) and inhaled nitric oxide (1A) as a standard treatment. We also suggest high positive end-expiratory pressure (2B), extracorporeal membrane oxygenation as a rescue therapy (2C), and neuromuscular blockage for 48 hours after starting mechanical ventilation (2B). The application of recruitment maneuver may reduce mortality (2B), however, the use of systemic steroids cannot reduce mortality (2B). In mechanically ventilated patients, we recommend light sedation (1B) and low tidal volume even without ARDS (1B) and suggest lung protective ventilation strategy during the operation to lower the incidence of lung complications including ARDS (2B). Early tracheostomy in mechanically ventilated patients can be performed only in limited patients (2A). In conclusion, of 12 recommendations, nine were in the management of ARDS, and three for mechanically ventilated patients.

Clinical Practice Guideline of Acute Respiratory Distress Syndrome / 대한중환자의학회지

There is no well-stated practical guideline for mechanically ventilated patients with or without acute respiratory distress syndrome (ARDS). We generate strong (1) and weak (2) grade of recommendations based on high (A), moderate (B) and low (C) grade in the quality of evidence. In patients with ARDS, we recommend low tidal volume ventilation (1A) and prone position if it is not contraindicated (1B) to reduce their mortality. However, we did not support high-frequency oscillatory ventilation (1B) and inhaled nitric oxide (1A) as a standard treatment. We also suggest high positive end-expiratory pressure (2B), extracorporeal membrane oxygenation as a rescue therapy (2C), and neuromuscular blockage for 48 hours after starting mechanical ventilation (2B). The application of recruitment maneuver may reduce mortality (2B), however, the use of systemic steroids cannot reduce mortality (2B). In mechanically ventilated patients, we recommend light sedation (1B) and low tidal volume even without ARDS (1B) and suggest lung protective ventilation strategy during the operation to lower the incidence of lung complications including ARDS (2B). Early tracheostomy in mechanically ventilated patients can be performed only in limited patients (2A). In conclusion, of 12 recommendations, nine were in the management of ARDS, and three for mechanically ventilated patients.

Clinical Practice Guideline of Acute Respiratory Distress Syndrome / 결핵및호흡기질환

There is no well-stated practical guideline for mechanically ventilated patients with or without acute respiratory distress syndrome (ARDS). We generate strong (1) and weak (2) grade of recommendations based on high (A), moderate (B) and low (C) grade in the quality of evidence. In patients with ARDS, we recommend low tidal volume ventilation (1A) and prone position if it is not contraindicated (1B) to reduce their mortality. However, we did not support high-frequency oscillatory ventilation (1B) and inhaled nitric oxide (1A) as a standard treatment. We also suggest high positive end-expiratory pressure (2B), extracorporeal membrane oxygenation as a rescue therapy (2C), and neuromuscular blockage for 48 hours after starting mechanical ventilation (2B). The application of recruitment maneuver may reduce mortality (2B), however, the use of systemic steroids cannot reduce mortality (2B). In mechanically ventilated patients, we recommend light sedation (1B) and low tidal volume even without ARDS (1B) and suggest lung protective ventilation strategy during the operation to lower the incidence of lung complications including ARDS (2B). Early tracheostomy in mechanically ventilated patients can be performed only in limited patients (2A). In conclusion, of 12 recommendations, nine were in the management of ARDS, and three for mechanically ventilated patients.

A Comparison of Clinical Characteristics between Adenoviral and Group A Streptococcal Pharyngitis in Children / 소아감염

PURPOSE: To compare the clinical characteristics and laboratory finding between adenoviral and group A streptococcal (GAS) pharyngitis. METHODS: A retrospective review of medical records was performed in the patients with adenovirus infection among those who were admitted for febrile respiratory disease from January 2011 to July 2013 and GAS pharyngitis among those who visited for symptoms of scarlet fever from August 2006 to July 2013. RESULTS: 179 patients (AV1 group) were diagnosed with adenoviral pharyngitis and 37 (AV2 group) of these patients had adenovirus single infection. 26 patients (GAS group) were diagnosed with scarlet fever. Adenoviral infection (AV2 group) developed in younger patients compared to GAS group (2.8+/-2.1 years vs. 5.4+/-1.8 years, P=0.000). Total durations of fever and admission were longer in AV2 (6.3+/-2.6 days vs. 3.3+/-1.9 days, P=0.000; 4.1+/-1.2 days vs. 1.9+/-1.8 days, P=0.000, respectively). WBC counts were higher in AV2 (11,449+/-5,680 cells/mm2 vs. 6,722+/-6,941 cells/mm2, P=0.000). CRP was not significantly different between AV2 and GAS group (3.8+/-3.2 mg/dL vs. 5.2+/-5.1 mg/dL, P=0.368). No difference was found between two groups in the percentage of antibiotics use (91.9% vs. 100%, P=0.261). CONCLUSION: Clinical characteristics and measures of inflammation in the laboratory findings were similar between adenoviral and GAS pharyngitis group. It is necessary to conduct the test for respiratory virus and bacteria in early stage to differentiate in the pharyngitis patients with leukocytosis and elevation of CRP level.

A Case of Hypersensitivity to Mosquito Bites without Peripheral Natural Killer Cell Lymphocytosis in a 6-Year-Old Korean Boy

Hypersensitivity to mosquito bites (HMB) is a rare disease characterized by intense skin reactions such as bulla and necrotic ulcerations at bite sites, accompanied by general symptoms such as high-grade fever and malaise occurred after mosquito bites. It has been suggested that HMB is associated with chronic Epstein-Barr virus (EBV) infection and natural killer (NK) cell leukemia/lymphoma. We describe here a Korean child who presented with 3-yr history of HMB without natural killer cell lymphocytosis. He has been ill for 6 yr with HMB. Close observation and examination for the development of lymphoproliferative status or hematologic malignant disorders is needed.

Comparison of Immune Response by Virus Infection and Vaccination to 2009 Pandemic Influenza A/H1N1 in Children

We aimed to compare the immune response induced by natural infection with 2009 pandemic influenza A/H1N1 (pH1N1) virus and by monovalent pH1N1 vaccination in children and adolescents. This cross-sectional clinical study was conducted at 3 hospitals in Korea from February to May 2010. A total of 266 healthy subjects aged from 6 months to 18 yr were tested for the presence of the antibody against pH1N1 using hemagglutination inhibition (HI) test. Information about pH1N1 vaccination and laboratory-confirmed pH1N1 infection history was obtained. The overall rate of HI titers of > or = 1:40 against pH1N1 was 38.7%, and the geometric mean titer (GMT) was 20.5. Immunogenicity of pH1N1 vaccination only was reflected by a 41.1% of seroprotection rate and a GMT of 22.5. Immunogenicity of natural infection only was reflected by a 61.0% of seroprotection rate and a GMT of 40.0. GMT was significantly higher in the subjects of natural infection group than in the subjects of pH1N1 vaccination group (P < 0.001). The immune responses induced by natural pH1N1 infection exceed those induced by pH1N1 vaccinations.

Detection of Human Herpesvirus-6 (HHV-6) in Cerebrospinal Fluid of a Patient with Fatal Status Epilepticus / 대한소아신경학회지

Human herpesvirus-6 (HHV-6) often causes mild illnesses, but is rarely associated with encephalitis or other fatal neurological conditions. We report a girl who died of a intractable status epilepticus from HHV-6. A 14-month-old girl presented with focal motor seizures in right extremities evolving to generalized convulsive status epilepticus. She had a history of mild diarrhea for 4 days and high fever for 2 days. Although she was treated with lorazepam, phenytoin, phenobarbital, and continuous midazolam infusion, generalized seizures continued for 3 hours after arrival. She became seizure free, but remained unconscious and ended up to death at the 44 days of hospitalization. The CSF HHV-6 DNA PCR turned out to be positive.

Evaluation of immunogenicity of the 2008-2009 seasonal influenza vaccines by microneutralization test / 소아과

PURPOSE: For evaluating the immunogenicity of an influenza vaccine, the microneutralization (MN) test has a higher sensitivity and specificity as compared to the hemagglutination inhibition (HI) test. However, the MN test is more time consuming and is difficult to standardize. We performed the MN test to determine its usefulness as an alternative or complementary test to the HI test for evaluating the immunogenicity of influenza vaccines. METHODS: We compared the MN test with the HI test using 50 paired samples taken from a previous clinical study (2008-2009) in Korean children under 18 years of age. RESULTS: The linear correlation coefficients of the 2 tests for H3N2, H1N1, and influenza B were 0.69, 0.70, and 0.66, respectively. We identified a high index of coincidence between the 2 tests. For an influenza vaccine, the postvaccination seroprotection rates and seroconversion rates determined by the MN test were 78.0% and 96.0%, 90% and 42.0%, and 42.0% and 48.0% for H3N2, H1N1, and influenza B, respectively. Geometric mean titer fold increases of H3N2, H1N1, and influenza B were 2.89, 5.04, and 4.29, respectively, and were 2.5-fold higher. We obtained good results in the evaluation of the immunogenicity of the 2008-2009 seasonal influenza vaccines. CONCLUSION: We found that the MN test was as effective as the HI test. Therefore, we suggest that the MN test can be used as an alternative or complementary test to the HI test for evaluating the immunogenicity of influenza vaccines.

Protective Field Efficacy Study of Influenza Vaccines for Korean Children and Adolescent in 2010-2011 Season / 소아감염

PURPOSE: We conducted a prospective comparative clinical study to determine the field efficacy of the 2010-2011 influenza vaccines [Influenza virus strains; A/California/7/2009 (H1N1), A/Perth/16/2009 (H3N2), B/Brisbane/60/2008] in healthy Korean children under 18 years of age. METHODS: In this study, we enrolled subjects aged between 6 months and 18 years and divided them into 2 study groups: a group who received the influenza vaccines (407 subjects), and a control group who did not receive the influenza vaccines (230 subjects). Ours was a multicenter study that involved 7 hospitals, including the Korea Cancer Center Hospital. The study was conducted between September 2010 and February 2011. We collected nasal wash or throat swab samples from subjects who presented with acute febrile respiratory or influenza-like illnesses at the hospital. We used PCR to confirm the presence of the influenza virus in the respiratory samples and characterize the virus type. RESULTS: In this study, we collected 22 respiratory samples from the influenza-vaccinated group and found 3 cases of influenza virus infection. Similarly, we collected 21 samples from the control group and found 12 cases of influenza virus infection among 10 subjects during the study period. We determined the field efficacy of the 2010-2011 seasonal influenza vaccines to be 83.2% in healthy Korean children and adolescents. CONCLUSION: In this study, we determined the field efficacy of the 2010-2011 seasonal influenza vaccines in healthy Korean children and adolescents. We found that the field efficacy of 2010-2011 seasonal influenza vaccines was adequate.

Analysis of Palivizumab Prophylaxis in Patients with Acute Lower Respiratory Tract Infection Caused by Respiratory Syncytial Virus / 소아감염

PURPOSE: The aim of this study was to identify the clinical characteristics of lower respiratory tract infection due to respiratory syncytial virus (RSV) in young children and to provide information for an effective guideline for palivizumab administration in Korea. METHODS: We reviewed medical charts of 167 patients under 3 years of age who were hospitalized in Dongguk University Ilsan Hospital for lower respiratory tract infection between January 2007 and February 2011. Diagnosis of the virus was made based on the multiplex real time polymerase chain reaction. RESULTS: There were 113 patients who were infected by respiratory syncytial virus. 90 patients were term infants and 23 patients were preterm infants. No difference was shown between term and preterm infants except the days of admission which was 9.0+/-6.0 days and 12.6+/-21.0 days respectively. In the preterm group their mean age at the time of admission was 5.21+/-4.9 months and the mean gestational age was 33.1+/-4.3 weeks, and the mean birth weight was 2,152+/-950 g. Only 4 patients were born under 28 weeks gestational age and were candidates for palivizumab administration. CONCLUSION: Most of the patients with severe RSV lower respiratory tract infection were term or near term infants who were not candidates for palivizumab prophylaxis. A nationwide study is needed to make a new risk stratified guideline for RSV prophylaxis for our country.

Clinical Characteristics of Hospitalized Pediatric Patients with 2009 Novel Influenza A Infection / 소아알레르기및호흡기학회지

PURPOSE: Novel influenza H1N1 A virus developed pandemic infection, and patients requiring hospitalization have rapidly increased because of severe clinical symptoms and signs. We describe the clinical features of hospitalized pediatric patients with novel influenza virus infection. METHODS: We reviewed the medical charts of 128 pediatric patients under the age of 16 who were hospitalized in Dongguk University Ilsan Hospital between September 2009 and February 2010. We compared the clinical features of the pneumonia and non-pneumonia groups of patients, and analyzed clinical difference according to M. pneumoniae coinfection and severity of pneumonia. RESULTS: The male to female sex ratio of the subjects was 2.2:1, and the average age was 6.2 years. Sixty-five patients (50.8%) had pneumonia and their average age was 6.7 years. Variables including duration of admission, total WBC counts, neutrophil percentage and CRP were significantly different between the 2 groups, however, the other variables were not. The number of patients diagnosed with severe pneumonia was 20 (30.8%). M. pneumoniae coinfection occurred in 24.6% of patients in the pneumonia group, however, it did not influence the severity of pneumonia. Underlying asthma was more significantly associated with severe pneumonia than with mild pneumonia. There was no death case. CONCLUSION: In this study, 2009 novel influenza infection was more prevalent in school-age boys. M. pneumoniae coinfection occurred frequently, however, it did not seem to influence disease severity. Patients with underlying asthma tend to develop severe pneumonia more frequently.