• Communications for Statistical Applications and Methods
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• v.21 no.6
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• pp.487-500
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• 2014

A new method to calculate the transmittable prevalence of an epidemic disease is proposed based on a back-calculation formula. We calculated the probabilities of reactivation and of parasitemia as well as transmittable prevalence (the number of persons with parasitemia in the incubation period) of malaria in South Korea using incidence of 12 years(2001-2012). For this computation, a new probability function of transmittable condition is obtained. The probability of reactivation is estimated by the least squares method for the back-calculated longterm incubation period. The probability of parasitemia is calculated by a convolution of the survival function of the short-term incubation function and the probability of reactivation. Transmittable prevalence is computed by a convolution of the infected numbers and the probabilities of transmission. Confidence intervals are calculated using the parametric bootstrap method. The method proposed is applicable to other epidemic diseases in other countries where incidence and a long incubation period are available. We found the estimated transmittable prevalence in South Korea was concentrated in the summer with 276 cases on a peak at the $31^{st}$ week and with about a 60% reduction in the peak from the naive prevalence. The statistics of transmittable prevalence can be used for malaria prevention programs and to select blood transfusion donors.

• Journal of Preventive Medicine and Public Health
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• v.7 no.2
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• pp.403-415
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• 1974

The author has investigated epidemiological features of human cases of epidemic encephalitis (E. E.) in the Republic of Korea and the status of antibody requisition in pre-and post-epidemic time. And virological and serological studies with regarding the relationship of E. E. infection between human and piglet, and field survey against its vector by means of virus isolation from mosquitoes were carried out. Finally, vaccine field trial against human population has also been evaluated in order to confirm its effectiveness. The results of the studies are summarized as follows : 1. The annual incidence of reported cases during the past 25 years (1949-1973) in the Republic of Korea has shown two patterns, one was typical cyclic incidence and the other one was irregular. Annual average morbidity and mortality rate per 100,000 population were 5.7 and 2.1 and fatality rate was 34.6% in typical cyclic years. 2. With regard to the geographical distribution of E. E., the province of Jeolla-Bug-Do illustrated the highest incidence regardless of the epidemic size. 3. The main epidemic period was between mid-August and mid-September (above 90% of the total number of cases). The first case was reported in middle of July and the epidemic ceased in late of October. 4. An analysis of the age distribution of cases of E. E., has shown that above 90% of the total cases occurred in the age groups under 14 years and it was noted that about its 54% were occurred in the age groups between 5-9 years group. 5. Through the Haemagglutination Inhibition (H-I) test for the laboratory diagnosis of E. E., it was found that higher H-I antibody titer was usually detected in the convalescent phase, 15 days after onset. 6. The H-I antibody survey against 563 healthy population by age groups during the pre-epidemic season showed that 422(75%) were less than H-I titer, 1:20 and 122(21.7%) were positive H-I titer, 1:20. Among the 94 American in Seoul who had not been in E. E. endemic area previously only one person had appeared sero-conversion as a H-I titer of 1:80 after post-epidemic season. 7. The E. E. virus could be isolated from the mosquitos pools-C, tritaeniorhyncus which were caught between late July and middle August. 8. E.E. Virus was also isolated from piglet blood on early August and H-I antibody conversion was occurred mostly on middle of August. 9. H-I antibody sero-conversion rate reached to high level when vaccine purified by mouse brain tissue inoculated, showing 98.9%. Higher antibody titer was acquired when booster inoculation was performed, Four fold rise of H-I add N-T antibodies was confirmed with 93.2% and 82.1% respectively.

• Journal of Korean Academy of Nursing
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• v.2 no.1
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• pp.73-85
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• 1971

A epidemiological study was conducted by author on 925 official reported patients with the first grade legal communicable disease during the period from January 1969 to December 1970 in all area of Kangwon province. As the results of this study, tile following conclusion were obtained. A) Typhoid fever 1. Of all 925 patients surveyed, typhoid fever showed the highest rate as 50.7 percent. 2. Age group from 10 to 14 years old showed the highest rates 3. High epidemic period was from June to September. 4. As for the occupational distribution, unemployed showed the highest rate as 63.2 percent, followed by-21.1 percent in farmer and 9.4 percent in student. 5. Most of all patients(93.7%) were isolated in their own house 6. The morbidity rate was 16.0 per 100, 000 population and case fatality rate was 1.76 percent 7. The mean of the duration from onset to diagnosis and carnation were 11.7$\pm$7.1 days and 25.1$\pm$13, 8 days respectively. 8. Main diagnostic method was almost the clinical examination B) Dysentery 1, Of all 925 patients surveyed, dysentery showed 44.4 percent 2. Age group from 0 to 9 years old showed the highest rate 3. High epidemic period of this disease was from April to August 4. As for the occupational distribution, unemployed showed the highest rate as 73.9 percent, followed by 17.7 person in farmers and 7.0 percent in student 5. the attack rate of agricultural area was higher than of fishing area 6. The mean of the duration from onset to diagnosis and crating duration were 10.4$\pm$4.3 days and 15.7$\pm$8.8 days respectively. 7. The morbidity rate and case fatality rate were 21.8 per 100.000 population and 1.46 percent, respectively. 8. Most of all patients were isolated in own house 9. Most of all patients (97.6%) were diagnosed by the clinical examination C) Diphtheria 1. As for the age distribution, 0-4 years old group showed the highest rate as 44.4 percent followed by 27.7 percent in 5-9 years old group and 22.2 percent in 10-14 years old group 3. Epidemic season was almost in autumn, winter and spring 3. The morbidity rate was 0.96 per 100.000 population and case fatality rate was high as 26.6 percent 4. 66.6 percent of this disease was isolated in their own house and the others were admitted in hospital D) Paratyphoid fever 1. Most of all patients were attacked below 20 years old 2. Epidemic season was almost was almost in late summer 3. The morbidity rate was 0.53 per 100.000 population 4. The mean of the duration from onset to diagnosis and crating duration were 18.3$\pm$1.3 day and 13.7$\pm$0.2 day. respectively.

• Journal of the Korean Data and Information Science Society
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• v.28 no.2
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• pp.297-307
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• 2017

The epidemic model is used to model the spread of disease and to control the disease. In this research, we utilize SEIR model which is one of applications the SIR model that incorporates Exposed step to the model. The SEIR model assumes that a people in the susceptible contacted infected moves to the exposed period. After staying in the period, the infectee tends to sequentially proceed to the status of infected, recovered, and removed. This type of infection can be used for research in cases where there is a latency period after infectious disease. In this research, we collected respiratory infectious disease data for the Middle East Respiratory Syndrome Coronavirus (MERSCoV). Assuming that the spread of disease follows a stochastic process rather than a deterministic one, we utilized the Poisson process for the variation of infection and applied epidemic model to the stochastic chemical reaction model. Using observed pandemic data, we estimated three parameters in the SIER model; exposed rate, transmission rate, and recovery rate. After estimating the model, we applied the fitted model to the explanation of spread disease. Additionally, we include a process for generating the Exposed trajectory during the model estimation process due to the lack of the information of exact trajectory of Exposed.

• Safety and Health at Work
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• v.13 no.3
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• pp.294-301
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• 2022

Background: In the early stage of the coronavirus disease 2019 (COVID-19) epidemic, small- and midsized enterprises (SMEs) may be an important transmission consideration. The study aimed to identify the pattern of COVID-19 prevention measures during the outbreaks in Daegu and Gyeongsangbuk-do at the early stage of COVID-19. Moreover, we investigated whether SME size and past experiences affected the preventive measures implemented in the region. Methods: A survey detailing the general characteristics and implementation of 12 preventive activities was conducted in 122 SMEs in Daegu and Gyeongsangbuk-do. The survey was analyzed by size and operation period. Results: The study subjects consisted of 53 (43.4%) workplaces with 1-5 employees, 50 (40.9%) workplaces with 6-30 employees, and 19 (15.6%) workplaces with 31-49 employees. The lowest three items among those surveyed were 'symptomatic workers to stay home for 3-4 days' (17.2%), 'work remotely' (18.9%), and 'video meetings' (20.5%). There were significant differences in the rate of several preventive measures implemented. The larger sized SMEs, the higher the number of implementations (p < 0.01). The operation period had no significant relationship with the implementation of preventive measures. The same pattern was observed in multiple generalized linear regression with covariate adjustment. Conclusion: Preventive measures among SMEs with fewer than 50 employees were identified. Even within SMEs, a gap in preventive measures according to size was confirmed. To prevent the spread of infection and protect workers' right to health, different support for different sized SMEs is necessary.

• Journal of applied mathematics & informatics
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• v.30 no.3_4
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• pp.635-646
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• 2012

This paper is concerned with an SIRS epidemic model with spatial diffusion and time delay representing the length of the immunity period. By using a new cross iteration scheme and Schauder's fixed point theorem, we reduce the existence of traveling wave solutions to the existence of a pair of upper-lower solutions. By constructing a newfashioned pair of upper-lower solutions, we derive the existence of a traveling wave solution connecting the uninfected steady state and the infected steady state.

• Journal of applied mathematics & informatics
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• v.27 no.3_4
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• pp.779-793
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• 2009

This paper deals with a delayed SEIRS epidemic model with pulse vaccination and crowded incidence rate. Moreover, the case of vertical and horizontal transmission is considered. By using the discrete dynamical system determined by the stroboscopic map, the exact infection-free periodic solution of the SEIRS model is obtained. Further, by employing the comparison arguments, we prove that under the condition that $R_*$ < 1 the infection-free periodic solution is globally attractive, and that under the condition that $R^*$ > 1 the disease is uniformly persistent, which means that after some period of time the disease will become endemic.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.1
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• pp.9-15
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• 2011

Highly pathogenic avian influenza could not be identified visually. It takes time to identify the symptoms by its incubation period. Without taking a quick step, the diffusion area of HPAI has dramatically increased, the extent of damage becomes bigger. In network research, the algorithm of finding the central node on the network applied to various diffusion of epidemic problems, was used in control system of tracing the diffusion path, blocking central nodes. This study tried to make the diffusion of HPAI network model for the crowded farms area, and reduce the diffusion rate to control the high-risk farms.

• Journal of the Korean Data and Information Science Society
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• v.20 no.1
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• pp.149-158
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• 2009

Tsutsugamushi fever occupies more than 80% of total fall epidemic diseases and has an incubation period of 1 or 2 weeks as well. We have assumed that the incubation period distribution is gamma and therefore, reach an agreement that the infected distribution is normal with ${\hat{\mu}}=309.92$, ${\hat{\sigma}}=14.154$ by back calculation method. The infection cases are found severely large around the month of October. The infection case distribution demonstrates the incidence number increasing rapidly and progresses fast during the month of November. In this study, we have calculated the future prevalence number of maximum 1,200 people by inferred infection probability and incubation period distribution with some sort of limitation that the trend of increasing incidence number is not taking into an account. We considered the SIRS model which is also known as epidemic model, familiar to interaction between epidemiological classes. Our estimated parameters converged well with the initial parameter values.

• Clinical and Experimental Pediatrics
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• v.48 no.5
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• pp.500-505
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• 2005

Purpose : This study was designed to estimate the prevalence of Mycoplasma pneumoniae infection during an epidemic period by means of examining the antibody conversion rate and to investigate the association of the antibody conversion with age, initial antibody titer, and atopy. Methods : We chose 191 children whose antibody titer to M. pneumoniae was negative, 1 : 40, or 1 : 80 during the first half of 2003. After the second half of 2003 when the M. pneumoniae epidemic occurred, follow-up collection of sera was performed during the first half of 2004. M. pneumoniae antibody titer was measured by Serodia-Myco II particle agglutination test. Results : Of 191 children, antibody conversion was detected in 83 children(43.5 percent). No significant difference was found between the conversion and non-conversion group with respect to age, sex and atopy. Dividing the subjects into four groups by age, results on the antibody conversion rate revealed no significant differences between the groups. Assessed by initial antibody titer, a diminished trend of conversion rate was observed in children with 1 : 80 titer but the difference was not significant. There was no significant difference in the antibody conversion rate between atopic and non-atopic children. Conclusion : Based on the antibody conversion rate in this study, the prevalence of M. pneumoniae infection during an epidemic period was estimated to be 43.5 percent. This high infection rate suggests that during an epidemic, we should bear in mind M. pneumoniae as an important etiologic agent for respiratory infection in children.