Non-Arteritic Ischemic Optic Neuropathy Following COVID-19 Vaccination in Korea: A Case Series

Background@#To report the clinical manifestations of non-arteritic anterior ischemic optic neuropathy (NAION) cases after coronavirus disease 2019 (COVID-19) vaccination in Korea. @*Methods@#This multicenter retrospective study included patients diagnosed with NAION within 42 days of COVID-19 vaccination. We collected data on vaccinations, demographic features, presence of vascular risk factors, ocular findings, and visual outcomes of patients with NAION. @*Results@#The study included 16 eyes of 14 patients (6 men, 8 women) with a mean age of 63.5 ± 9.1 (range, 43–77) years. The most common underlying disease was hypertension, accounting for 28.6% of patients with NAION. Seven patients (50.0%) had no vascular risk factors for NAION. The mean time from vaccination to onset was 13.8 ± 14.2 (range, 1–41) days. All 16 eyes had disc swelling at initial presentation, and 3 of them (18.8%) had peripapillary intraretinal and/or subretinal fluid with severe disc swelling. Peripapillary hemorrhage was found in 50% of the patients, and one (6.3%) patient had peripapillary cotton-wool spots. In eight fellow eyes for which we were able to review the fundus photographs, the horizontal cup/ disc ratio was less than 0.25 in four eyes (50.0%). The mean visual acuity was logMAR 0.6 ± 0.7 at the initial presentation and logMAR 0.7 ± 0.8 at the final visit. @*Conclusion@#Only 64% of patients with NAION after COVID-19 vaccination have known vascular and ocular risk factors relevant to ischemic optic neuropathy. This suggests that COVID-19 vaccination may increase the risk of NAION. However, overall clinical features and visual outcomes of the NAION patients after COVID-19 vaccination were similar to those of typical NAION.

Short-Term Effectiveness of Oral Nirmatrelvir/Ritonavir Against the SARS-CoV-2 Omicron Variant and Culture-Positive Viral Shedding

Background@#Information on the effectiveness of nirmatrelvir/ritonavir against the omicron is limited. The clinical response and viral kinetics to therapy in the real world need to be evaluated. @*Methods@#Mild to moderate coronavirus disease 2019 (COVID-19) patients with risk factors for severe illness were prospectively enrolled as a treatment group with nirmatrelvir/ritonavir therapy versus a control group with supportive care. Serial viral load and culture from the upper respiratory tract were evaluated for seven days, and clinical responses and adverse reactions were evaluated for 28 days. @*Results@#A total of 51 patients were analyzed including 40 in the treatment group and 11 in the control group. Faster symptom resolution during hospitalization (P= 0.048) was observed in the treatment group. Only minor adverse reactions were reported in 27.5% of patients. The viral load on Day 7 was lower in the treatment group (P = 0.002). The viral culture showed a positivity of 67.6% (25/37) vs. 100% (6/6) on Day 1, 0% (0/37) vs. 16.7 (1/6) on Day 5, and 0% (0/16) vs. 50.0% (2/4) on Day 7 in the treatment and control groups, respectively. @*Conclusions@#Nirmatrelvir/ritonavir against the omicron was safe and resulted in negative viral culture conversion after Day 5 of treatment with better symptomatic resolution.

Temporal Arteritis with Diagnostic Brain Magnetic Resonance Imaging

Purpose@#To report a case of arteritic anterior ischemic optic neuropathy diagnosed with brain magnetic resonance imaging (MRI) for temporal arteritis instead of temporal artery biopsy.Case summary: An eighty-three years old female visited our clinic for right blurred vision for 2 weeks ago with occipital headache for 4 months and mastication problems. Initial best corrected visual acuity was 0.1 in right eye. She had right inferior altitudinal visual field defect and superior pale optic disc swelling with few cotton wool spots were checked. In serologic tests, erythrocyte sedimentation rate, C reactive peptide, and rheumatoid factor were increased, and fluorescent antinuclear antibody was positive. We performed high resolution brain MRI which could find superficial temporal artery’s luminal signal. In MRI image, we could find loss of intraluminal signal intensity void with total luminal obstruction. We assumed as arteritic anterior ischemic optic neuropathy and high dose intravenous steroid was done. Visual acuity of right eye was 0.9 and central scotoma was improved 1 week after intravenous steroid. We changed to oral steroid with tapering and added oral azathioprine. After 11 months of oral steroid use, her visual acuity was 0.9 in right eye and inferior altitudinal visual field defect was much improved. @*Conclusions@#A patient suspected anterior ischemic optic neuropathy was diagnosed by brain MRI with abnormalities in superficial temporal artery. Visual acuity and visual field defect were improved by steroid and immunosuppressive treatment for arteritic anterior ischemic optic neuropathy.

Temporal Arteritis with Diagnostic Brain Magnetic Resonance Imaging

Purpose@#To report a case of arteritic anterior ischemic optic neuropathy diagnosed with brain magnetic resonance imaging (MRI) for temporal arteritis instead of temporal artery biopsy.Case summary: An eighty-three years old female visited our clinic for right blurred vision for 2 weeks ago with occipital headache for 4 months and mastication problems. Initial best corrected visual acuity was 0.1 in right eye. She had right inferior altitudinal visual field defect and superior pale optic disc swelling with few cotton wool spots were checked. In serologic tests, erythrocyte sedimentation rate, C reactive peptide, and rheumatoid factor were increased, and fluorescent antinuclear antibody was positive. We performed high resolution brain MRI which could find superficial temporal artery’s luminal signal. In MRI image, we could find loss of intraluminal signal intensity void with total luminal obstruction. We assumed as arteritic anterior ischemic optic neuropathy and high dose intravenous steroid was done. Visual acuity of right eye was 0.9 and central scotoma was improved 1 week after intravenous steroid. We changed to oral steroid with tapering and added oral azathioprine. After 11 months of oral steroid use, her visual acuity was 0.9 in right eye and inferior altitudinal visual field defect was much improved. @*Conclusions@#A patient suspected anterior ischemic optic neuropathy was diagnosed by brain MRI with abnormalities in superficial temporal artery. Visual acuity and visual field defect were improved by steroid and immunosuppressive treatment for arteritic anterior ischemic optic neuropathy.

Seroprevalence of Anti-SARS-CoV-2 Antibodies among Outpatients in Southwestern Seoul, Korea

Serosurveillance studies reveal the actual disease burden and herd immunity level in the population. In Seoul, Korea, a cross-sectional investigation showed 0.07% anti-severe acute respiratory syndrome coronavirus-2 antibody seropositivity among 1,500 outpatients of the university hospitals. Low seroprevalence reflects well-implemented social distancing.Serosurveillance should be repeated as the pandemic progresses.

Surgical Outcomes of Modified Medial Rectus Resections in Recurrent Intermittent Exotropia

PURPOSE: To evaluate the outcomes of modified medial rectus (MR) resection using a lowered amount of MR resection for recurrent exotropia after bilateral lateral rectus (LR) recessions. METHODS: Fifty-six patients, who underwent MR resection from 2003 to 2017 for recurrent exotropia after bilateral LR recessions, were included. MR resection was performed using modified MR resection with a smaller amount of resection than the standard of 4 mm resection at 20 prism diopters (PD) of exotropia. Postoperative surgical results at 1 month, 6 months, 1 year and 2 years were classified as a success (5 PD esotropia [ET]-10 PD exotropia [XT]), overcorrection (>5 PD ET), and undercorrection (>10 PD XT). The clinical factors affecting surgical results at postoperative 6 month and 2 years were also evaluated. RESULTS: The success rate was 78.2% at postoperative 1 month and 87.5% at postoperative 6 months. The overcorrection rate was 21.8% and the undercorrection rate was 0% at postoperative 1 month. At postoperative 6 months, the overcorrection rate decreased to 0% and the undercorrection rate was 12.5%. The success rate was 85.7% at postoperative 1 year and 66.6% at postoperative 2 years. There was no clinical factor affecting the surgical outcomes except the ocular alignment at postoperative 1 month. The deviation at postoperative 1 month was more esotropic in patients with success at postoperative 6 months and 2 years than that in patients with undercorrection (p < 0.05). CONCLUSIONS: The modified MR resection showed favorable results of 87.5% at postoperative 6 months and 85.7% at 1 year. The angle of deviation at postoperative 1 month was an indicator of subsequent surgical outcomes.

Knowledge, Confidence, and Learning Needs Regarding Advance Directives among Hospital Nurses / 중환자간호학회지

PURPOSE: Nurses' knowledge regarding advance directives may affect their administration of and confidence towards end of life care. This study aimed to describe the relationships of knowledge, confidence, and learning needs with advance directives among hospital nurses.METHOD: This cross-sectional study was performed at a tertiary university hospital in Seoul between September 25 and October 14, 2017. Convenience sampling was used to recruit nurses who provided bedside care and had at least 1 year of clinical experience. We used a validated self-report questionnaire.RESULTS: The mean score of knowledge, confidence and learning needs were 5.00±1.73, 29.81±7.52, and 64.54±8.48 respectively. Hospital nurses' knowledge, confidence and learning needs were significantly different according to age, job position, educational level and perceived advance directives. Knowledge regarding advance directives was significantly associated with confidence (r = .27, p < .001) and learning needs (r = .16, p = .005).CONCLUSION: Knowledge regarding advance directives was relatively low compared to the findings of previous studies. Therefore, nurses should be knowledgeable and encouraged to initiate advance directives. It is necessary to develop a standardized educational program regarding advance directives based on Korean cultures.

Long-term Intraocular Pressure Elevation after Primary Angle Closure Treated with Early Phacoemulsification

PURPOSE: To assess long-term changes in intraocular pressure (IOP) and the development of glaucoma after early phacoemulsification in acute primary angle closure. METHODS: Retrospective chart review of acute primary angle closure patients treated with phacoemulsification in attack eyes versus fellow eyes. Within a month after the angle closure attack, all subjects underwent cataract surgery and were divided into two groups: group A received cataract surgery on their attack eyes. Group B also received cataract surgery on their fellow eye after phacoemulsification of the attack eyes. Study outcomes were the prevalence of IOP rise (occurrence of IOP >21 mmHg) and the incidence of newly developed glaucoma. RESULTS: Eighty-nine eyes were included, with 62 attack eyes in group A and 27 fellow eyes in group B. Group A (14 eyes, 22.58%) had a higher cumulative rate of IOP rise than group B (3 eyes, 11.11%) at 12 months (p = 0.001). Newly developed glaucoma was not observed in group B; however, 6 patients in group A developed glaucoma during the 12-month follow-up period (p < 0.001). CONCLUSIONS: The attack eyes treated with phacoemulsification showed a significantly higher prevalence of IOP rise and newly developed glaucoma than fellow eyes that received phacoemulsification. These findings suggest that there is a possibility of IOP rise and development of glaucoma even when angle closure and successful IOP control have apparently been achieved after phacoemulsification.

Assessment of Tissue Perfusion with Blood Oxygenation Level-Dependent Magnetic Resonance Imaging in Critical Limb Ischemia

No abstract available.

Relationship between Palpebral Fissure Height and Corneal Astigmatism of Epiblepharon

PURPOSE: To study the effect of plapebral fissure height on astigmatism in epiblepharon patients. METHODS: The study consisted of 68 eyes of 34 patients who were diagnosed with epiblepharon and 88 eyes of 44 patients who had normal eyelids from September 2012 to July 2013. Data on palpebral fissure height and refractive errors were compared between the epiblepharon group and the control group. Epiblepharon patients were further divided into two subgroups depending on the degree of preoperative corneal erosion in order to study the effects of corneal erosion on corneal astigmatism. RESULTS: The mean age was 5.6 ± 2.2 years in the epiblepharon group and 6.1 ± 1.5 years in the control group (p = 0.339). The mean astigmatism was 2.28 ± 1.54 D in the epiblepharon group and 0.91 ± 1.07 D in the control group. The epiblepharon group showed higher astigmatism than the control group (p < 0.001). The mean palepebral fissure height was 6.70 ± 1.19 mm in the epiblepharon group and 7.63 ± 1.06 mm in the control group. The epiblepharon group exhibited smaller palpebral fissure height than the control group (p < 0.001). In the palpebral fissure height subgroups of the epiblepharon group, the <7.0 mm group showed higher astigmatism than the ≥7.0 mm group (p = 0.026). Higher astigmatism was associated with smaller palpebral fissure height (p = 0.022). CONCLUSIONS: Patients with epiblepharon had significantly higher corneal astigmatism, and higher astigmatism was associated with smaller palpebral fissure height.

Superior Cervical Sympathetic Ganglion: Normal Imaging Appearance on 3T-MRI

OBJECTIVE: To identify superior cervical sympathetic ganglion (SCSG) and describe their characteristic MR appearance using 3T-MRI. MATERIALS AND METHODS: In this prospective study, we recruited 53 consecutive patients without history of head and neck irradiation. Using anatomic location based on literature review, both sides of the neck were evaluated to identify SCSGs in consensus. SCSGs were divided into definite (medial to internal carotid artery [ICA] and lateral to longus capitis muscle [LCM]) and probable SCSGs based on relative location to ICA and LCM. Two readers evaluated signal characteristics including intraganglionic hypointensity of all SCSGs and relative location of probable SCSGs. Interrater and intrarater agreements were quantified using unweighted kappa. RESULTS: Ninety-one neck sites in 53 patients were evaluated after exclusion of 15 neck sites with pathology. Definite SCSGs were identified at 66 (73%) sites, and probable SCSGs were found in 25 (27%). Probable SCSGs were located anterior to LCM in 16 (18%), lateral to ICA in 6 (7%), and posterior to ICA in 3 (3%). Intraganglionic hypointensity was identified in 82 (90%) on contrast-enhanced fat-suppressed T1-weighted images. There was no statistical difference in the relative location between definite and probable SCSGs of the right and left sides with intragnalionic hypointensity on difference pulse sequences. Interrater and intrarater agreements on the location and intraganglionic hypointensity were excellent (κ-value, 0.749-1.000). CONCLUSION: 3T-MRI identified definite SCSGs at 73% of neck sites and varied location of the remaining SCSGs. Intraganglionic hypointensity was a characteristic feature of SCSGs.

Giant hypothalamic hamartoma associated with an intracranial cyst in a newborn

We report the case of a giant hypothalamic hamartoma with a large intracranial cyst in a neonate. On ultrasonography, the lesion presented as a lobulated, mass-like lesion with similar echogenicity to the adjacent brain parenchyma, located anterior to the underdeveloped and compressed left temporal lobe, and presenting as an intracranial cyst in the left cerebral convexity without definite internal echogenicity or septa. The presence of a hypothalamic hamartoma and intracranial neurenteric cyst were confirmed by surgical biopsy. The association of a giant hypothalamic hamartoma and a neurenteric cyst is rare. Due to the rarity of this association, the large size of the intracranial cyst, and the resulting distortion in the regional anatomy, the diagnosis of the solid mass was not made correctly on prenatal high-resolution ultrasonography.

Complex Hemangioma of the Breast: Case Report, with Imaging Findings

Vascular tumors in the breast are rare, and most can be classified as being either angiosarcomas or hemangiomas. Hemangiomas are benign vascular tumors that are usually identified incidentally. Here, we are reporting on a case of a complex hemangioma of the breast, and describing the mammography, ultrasonography, and magnetic resonance imaging findings for this patient.

Comparison of Patient Characteristics in Thyroid-Associated Ophthalmopathy with and without Strabismus

PURPOSE: To determine immunochemical and clinical differences in thyroid-associated ophthalmopathy (TAO) patients with restrictive strabismus and without strabismus. METHODS: A retrospective chart review of 15 TAO patients with strabismus (25 eyes) and 24 TAO patients without strabismus (39 eyes) who presented to the Ophthalmology Clinic between August 2011 and December 2013 was performed. Visual acuity, intraocular pressure (IOP), Hertel exophthalmometry, soft tissue score, and enlargement of extraocular muscles on computed tomography (CT) were obtained and compared in each group. Thyroid related autoantibody (thyroid-stimulating hormone receptor antibody, TRAb; thyroid peroxidase antibody, TPOAb; anti-thyroglobulin antibody, TgAb) titers and positive rates were obtained at the time of diagnosis or before treatment and analyzed. RESULTS: The gender and smoking proportion were not significantly different between the 2 groups. The mean age of TAO patients with strabismus was 52.53 years and of TAO patients without strabismus 40.33 years (p = 0.004). The differences in visual acuity and IOP between the 2 groups were not significant. Hertel exophthalmometry showed less proptotis in the TAO with strabismus group than the TAO without strabismus group (16.84 mm versus 18.67 mm). The soft tissue score was not significantly different. The extraocular muscle enlargement rate of TAO with strabismus was significantly higher than in TAO without strabismus group. In the TAO with strabismus group, TRAb level was higher than in the TAO without strabismus group (p = 0.021). CONCLUSIONS: The TAO with strabismus group was older and had higher positive rate, level of TRAb, and extraocular muscle enlargement rate on CT than the TAO without strabismus group. Furthermore, proptosis was less definite in the TAO with strabismus group.

Awareness and Ethical Attitudes Toward 'Do-Not-Resuscitate (DNR)' for Cancer Patients

PURPOSE: This descriptive study was conducted to investigate awareness and attitudes toward 'Do-Not-Resuscitate (DNR)'. METHODS: Study data were collected from July 24 to September 30, 2011 using structured questionnaires. Study subjects were 209 patients suffering from cancer at "C" Univ. hospital located in Seoul and Cancer Patient Coalition in Seoul. The purpose of the study was explained directly to them. All the data of 209 questionnaires were collected and analyzed without dropping out. RESULTS: In terms of awareness toward DNR, 61.5% said DNR is "necessary" because "their recoveries are impossible" (51.7%) and "they want dignified deaths" (41.1%). When it comes to ethical attitudes toward DNR according to demographic characteristics, there were significant differences both between genders (p<.032) on "Medical staff should tell hopeless patients their conditions openly" and between level of education and monthly income (p<.013) on "DNR decision should be made according to the guideline, if needed". CONCLUSION: The result of this study suggests that decisions on DNR should be made not by only families and doctors but by patients themselves as well. For this, sufficient explanations and education programs for DNR need to be developed and DNR decision including both patient's and family's demand should be standardized.

Correction of Hypertropia Coexisting with Intermittent Exotropia

PURPOSE: To investigate the clinical features associated with hypertropia and report the surgical outcomes of hypertropia coexisting with exotropia. METHODS: We reviewed the medical records of 148 patients with intermittent exotropia coexisting with hypertropia over 4 PD who received exotropia surgery. The cases accompanied by apparent paralytic strabismus such as superior oblique palsy were excluded. Patients were divided into group I(clinically diagnosed hypertropia) and group II (non-specific hypertropia) and the clinical features of coexisting hypertropia and surgical outcomes were analyzed. RESULTS: Among the 148 patients, group Iconsisted of 38 patients (26%) and group II of 110 patients (74%). The average amount of preoperative hypertropia angle in primary gaze was 9.58 +/- 3.89 PD and 6.62 +/- 2.69 PD in group I and II, respectively. Group I included 12 patients with dissociated vertical deviation (DVD), 10 patients with unilateral inferior oblique overaction, 13 patients with asymmetric bilateral inferior oblique overaction and 3 patients with superior oblique overaction. Group II included 19 patients with comitant hypertropia (17%), head tilt positive pattern (simulated superior oblique palsy) was found in 84 patients (76.3%) and variable incomitance was observed. In group I, 29 patients received simultaneous horizontal muscle with hypertropia surgery. Postoperative hypertropia angle in group I was 1.41 +/- 2.93 PD and 4 cases were considered surgical failure. In group II, hypertropia was resolved with horizontal muscle surgery only and the amount of postoperative hypertropia was 0.45 +/- 1.60 PD. CONCLUSIONS: In this study, vertical deviations in intermittent exotropia with concomitant hypertropia related to obvious oblique muscle dysfunction or DVD were corrected effectively by oblique or vertical rectus muscle surgery. Nonspecific hypertropia can be resolved after horizontal muscle surgery alone, however, for precise differential diagnosis, careful examination for variable clinical features is necessary before determining surgery.

Side Effects after the Use of Cyclopentolate for Cycloplegic Refraction

PURPOSE: To investigate the frequency of side effects due to the use of cyclopentolate for cycloplegic refraction. METHODS: For 4 months, temperature change and adverse effects in 157 children who visited the pediatric ophthalmology clinic of a university hospital for cycloplegic refraction using cyclopentolate were observed. Topical 1% cyclopentolate was instilled 5 times at 5 minute intervals and temperature measured before and after administration using a tympanic thermometer. Side effects such as facial flushing, skin rash, and central nervous system disorders were recorded while cycloplegic refraction was performed. RESULTS: The mean temperature was increased 36.67 +/- 0.10degrees C to 36.90 +/- 0.09degrees C, but no fever exceeded 38degrees C. Seventeen (10.83%) patients experienced side effects including facial flushes (n = 6), temperature change (n = 5), abnormal central nervous system symptoms (n = 4), and a visible skin rash (n = 2). No patient experienced more than 1 side effect and long term adverse effects were not observed. CONCLUSIONS: The incidence of side effects due to cyclopentolate instillation for cycloplegic refraction was 10.83% in children. Although side effects due to cyclopentolate disappeared without any treatment, cafeful monitoring for their occurrence is necessary.

A Study of Ocular Disease and Treatment in Patients with Developmental Disability

PURPOSE: To evaluate ocular abnormalities in children with developmental disability and to find out whether any correlation exists between developmental disability and surgical outcome. METHODS: Totally 43 patients with the diagnosis of developmental disability were enrolled in this retrospective study. RESULTS: Mean follow-up was 4.54 +/- 2.35 year. 20 patients had exodeviation, 15 patients had esodeviation, 10 patients had dissociated vertical deviation and 4 patients had dyskinetic strabismus. 21 patients had surgery and the mean deviation angle was decreased from 36.67 +/- 15.70 PD to 5.33 +/- 5.93 PD in exotropia and 56.25 +/- 8.54 PD to 5.75 +/- 4.65 PD in esotropia. Refractive error was found in 33 patients (88.4%). 26 patients (60.5%) had monocular amblyopia and 17 patients (65.38%) showed improvement of visual acuity after treatment. CONCLUSIONS: Exotropia is the most common type strabismus in patients with developmental disability and dyskinetic strabismus is found in cerebral palsy. Strabismus Surgery for patients with stable angle deviation and amblyopia treatment is effective in children with developmental disability. However decision for surgery should be made after a long follow up period.

Southern Analysis after Long-range PCR: Clinical Application in Korean Patients with Myotonic Dystrophy 1

PURPOSE: Myotonic dystrophy 1 (DM1, OMIM 160900) is an autosomal-dominant muscular disorder caused by an expansion of CTG repeats in the 3' UTR of the DMPK gene. Variable expansions of CTG repeats preclude the accurate determination of repeat size. We tried to show the clinical and analytical validity of the application of Southern blotting after long-range PCR was demonstrated in Korean DM1 patients. MATERIALS AND METHODS: The Southern blotting of long-range PCR was applied to 1,231 cases with clinical suspicion of DM1, between 2000 and 2011. PCR was performed using genomic DNA with forward 5'-CAGTTCACAACCGCTCCGAGC-3' and reverse 5'-CGTGGAGGATGGAACACGGAC-3' primers. Subsequently, the PCR fragments were subjected to gel electrophoresis, capillary transfer to a nylon membrane, hybridization with a labeled (CAG)10 probe. The correlation between clinical manifestations and the CTG repeat expansions were analyzed. RESULTS: Among a total of 1,231 tested cases, 642 individuals were diagnosed with DM1 and the range of the detected expansion was 50 to 2,500 repeats; fourteen cases with mild DM1 (75+/-14 repeats), 602 cases with classical DM1 (314+/-143 repeats), and 26 cases with congenital DM1 (1,219+/-402 repeats). The positive and negative predictive values were 100%. The age at test requested and the CTG repeat numbers were inversely correlated (R=-0.444, P<0.01). CONCLUSION: This study indicates that Southern blotting after long-range PCR is a reliable diagnostic method DM1.

Occurrence and characterization of oseltamivir-resistant influenza virus in children between 2007-2008 and 2008-2009 seasons / 소아과

PURPOSE: There was a global increase in the prevalence of oseltamivir-resistant influenza viruses during the 2007-2008 influenza season. This study was conducted to investigate the occurrence and characteristics of oseltamivir-resistant influenza viruses during the 2007-2008 and 2008-2009 influenza seasons among patients who were treated with oseltamivir (group A) and those that did not receive oseltamivir (group B). METHODS: A prospective study was conducted on 321 pediatric patients who were hospitalized because of influenza during the 2007-2008 and 2008-2009 influenza seasons. Drug resistance tests were conducted on influenza viruses isolated from 91 patients. RESULTS: There was no significant difference between the clinical characteristics of groups A and B during both seasons. Influenza A/H1N1, isolated from both groups A and B during the 2007-2008 and 2008-2009 periods, was not resistant to zanamivir. However, phenotypic analysis of the virus revealed a high oseltamivir IC50 range and that H275Y substitution of the neuraminidase (NA) gene and partial variation of the hemagglutinin (HA) gene did not affect its antigenicity to the HA vaccine even though group A had a shorter hospitalization duration and fewer lower respiratory tract complications than group B. In addition, there was no significant difference in the clinical manifestations between oseltamivir-susceptible and oseltamivir-resistant strains of influenza A/H1N1. CONCLUSION: Establishment of guidelines to efficiently treat influenza with oseltamivir, a commonly used drug for treating influenza in Korean pediatric patients, and a treatment strategy with a new therapeutic agent is required.