Epidemiology and Health

Original Article

Epidemiological Characteristics of Imported Influenza A (H1N1) Cases during the 2009 Pandemic in Korea: Jun Kil Choi, Sang Won Lee, Bo Youl Choi; Epidemiol Health. 2012;34:e2012009. Published online December 31, 2012; DOI: https://doi.org/10.4178/epih/e2012009

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Abstract

<sec><title>OBJECTIVES</title>Quarantine measure for prevention of epidemic disease and further evaluations of their efficiency are possible only by elaborating analyses of imported cases. The purpose of this study was to analyze descriptive epidemiological characteristics of pandemic influenza A (H1N1) cases imported to Korea.</sec><sec><title>METHODS</title>We collected two sets of data. The first set, comprised daily reported cases of H1N1 obtained from local cities in accordance with government policy about mandatory reporting of all H1N1 cases during May 1 to August 19, 2009. The second set, including 372 confirmed imported H1N1 cases, identified from 13 National Quarantine Stations in the Korea Centers for Disease Control and Prevention from May 24 to December 31, 2009. However, given the lack of information on the nature of the imported H1N1 cases from the two data sets during the over lapping period from May 24 to August 19, we express the number of imported cases as a range for this period.</sec><sec><title>RESULTS</title>We estimated that the number of imported H1N1 cases from May 1 to August 19, 2009, was between 1,098 and 1,291 and the total number of cases was 2,409 to 2,580. We found the number of imported cases was beginning to diminish as of August. A analysis of the second data set showed that the distribution of sex was similar (males 50.7%, females 49.3%) and the age distribution from 20 to 59 was 61.5% and that of 60 and over was 0.8% of the 372 cases. We identified 25 countries where people infected with H1N1 traveled and 67.5% were in Asia. But the proportion of cases (/1,000) by region shows Oceania (0.199), South America (0.118), Southeast Asia (0.071), North America (0.049), Europe (0.035), and Northeast Asia (0.016) in that order. The order of H1N1 peaking was the Southern Hemisphere, Tropics, and the Nothern Hemisphere.</sec><sec><title>CONCLUSIONS</title>This study provided information that could make possible the evaluation of the government quarantine measure for stopping imported disease from causing community-acquired spread in the future.</sec>

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Social Distancing and Transmission-reducing Practices during the 2019 Coronavirus Disease and 2015 Middle East Respiratory Syndrome Coronavirus Outbreaks in Korea
Won Mo Jang, Deok Hyun Jang, Jin Yong Lee
Journal of Korean Medical Science.2020;[Epub] CrossRef

Reviews

A review of mathematical models and strategies for Pandemic Influenza Control.: Seong Sun Kim, Sang Won Lee, Bo Youl Choi; Korean J Epidemiol. 2008;30(2):156-167. Published online December 31, 2008; DOI: https://doi.org/10.4178/kje.2008.30.2.156

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Abstract

Despite many countries' current effort to make mathematical models for pandemic influenza (PI) and predict the impact of an outbreak, natural history of PI is remains incomplete, so that any assumption or model is unable to completely predict the impact. Our objective is to review and summarize previous studies on parameters and models of PI, and to make suggestions for the controls in order to decrease the impact of PI. We searched PubMed to retrieve literature about the PI model systematically . Reference lists and review papers on the topic were searched, as well. We found 35 articles that examined the PI model over the period of May 2003 to August 2008. We reviewed modelling methods that were focused on the PI, and their parameters i.e. latent period, and basic reproductive number (R0). Then, we summarized PI controls: antivirals, vaccines, and social distancing. Recent studies showed with mathematical models that Targeted Antiviral Prophylaxis (TAP) is the best strategy for containing PI at the source. In case of an outbreak, quick measures of social distancing, including therapeutic and prophylatic antiviral for cases and closing contacts - school closure, workplace closure, border quarantine, and home isolation - were found to be most effective. We reviewed strengths and weaknesses of models that are adaptable in Korea, and summarized their parameters. It is our hope that these strategies with various interventions give important information for future preparation for and response to PI in Korea.

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Stochastic methods for epidemic models: An application to the 2009 H1N1 influenza outbreak in Korea
Hyojung Lee, Sunmi Lee, Chang Hyeong Lee
Applied Mathematics and Computation.2016; 286: 232. CrossRef

A study on epidemiological characteristics and control methods of EHEC infection in Korea.: Sang Won Lee, Bok Kwon Lee, Yong Jae Lee, Hee Soo Lee, Suk Chan Jung, Kwak Hyo Sun, Bo Youl Choi; Korean J Epidemiol. 2005;27(1):37-52.

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Abstract PDF: Abstract
E. coli is a bacterium that is commonly found in the gut of humans and warm-blooded animals. Most strains of E. coli are harmless. But some strains such as Enterohaemorrhagic E. coli(EHEC), can cause severe food borne disease. It is transmitted to humans primarily through consumption of contaminated foods, such as raw or undercooked ground meat. There is no widely agreed definition of when a shiga-toxin producing E. coli is considered to be an EHEC. But in Korea, the word "EHEC", "STEC", "VTEC" are often used as same meaning, which refer to the E.coli those producing shiga-toxin. We suggest the term STEC refers to those E. coli produce one or more shiga-toxins(stx), and the term EHEC refers only to STEC that cause a clinical illness. EHEC infection were designated as the class 1 notifiable disease in Korea in 2000. Although EHEC/STEC cases were not common in Korea, the number of STEC infection cases reported has increased since 2001. From 2001 to 2004, the number of STEC infection cases in Korea were 11, 8, 52, 118 respectively. These cases included 17 due to E. coli O157, 136 due to E. coli, serogroup non-O157, and 15 due to E. coli that were not serogrouped. The most common serotype implicated is E. coli O91 without virulent factor and clinical symptoms. But those cases involve in one epidemic in primary school in 2004. STEC infections in Korea occur in all age groups, with the highest frequencies in children less than 5 years old. Healthy cattle are the main animal reservoir for STEC and they harbor the organism as part of the bowel flora. The proportion of STEC in E. coli in animal feces was examined by using stool samples from 283 Korean beef cattle on 27 farms, 169 milk cattle on 28 frams, 455 swine on 50 farms. As determined by culture and toxin assay, the proportion of STEC was 25.8%(16 STEC/62 E. coli) in milk cattle, 18.8%(19 STEC/101 E.coli) in Korean beef cattle, 14.0%(25 STEC/178 E. coli) in swine. Effective surveillance of EHEC/STEC in humans is essential in order to protect the public health. EHEC infection is notifiable in many countries including USA, Japan, and Belgium, Finland, Italy, Netherlands, and the United Kingdom(UK), have sentinel systems. England, Wales, and Scotland have comprehensive national laboratory reporting schemes for STEC. And there has been an increase in the number of reported cases and outbreaks during the past decades in many countries Prevention of STEC infection requires control measures at all stages of surveillace, investigations and special pathogen tracing such as PulseNet.; Summary

Original Articles

A Epidemic Survey of the Shigellosis in Jeju Island during the First Half of Year 2000.: Jong Myon Bae, Sang Won Lee, Byung Guk Yang, Seong Chul Hong, Geun Ryang Bae, Sung Hack Kang; Korean J Epidemiol. 2001;23(1):80-80.

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Abstract PDF: Abstract
PURPOSE
A field investigation was done to evaluate the level of the epidemic of Shigellosis in Jeju Island during the first half of year 2000.
METHODS
Confirming the Shigellosis was done by the structured questionnaire and the result of rectal swab for the residents having a diarrhea.
RESULTS
As the confirmed patients with Shigella sonnei were 933 from 25 April to 14 August 2000, the crude incidence rate was 174 per 100,000 persons. The highest incidence rate was shown in 5-9 year-old group. Especially the south area of Jeju Island, called as Namjejugun, had the major epidemic occurrence.
CONCLUSIONS
The huge and chronic epidemic of Shigellosis was confirmed. The nature of this epidemic suggested that the endemic occurrence had been existed in Jeju Island.; Summary

An Epidemiologic Investigation of Shigella Sonnei Outbreak at a Primary School in Taegu city.: Byung Yeol Chun, Keon Yeop Kim, Ki Soo Park, Sang Won Lee, Young Joo Hur, Sun Hee Park, Ki Sang Kim, Sang Won Lee, Soon Ja Kim, Young Sook Hong; Korean J Epidemiol. 2000;22(2):101-107.

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Abstract PDF: Abstract
PURPOSE
S: This study was conducted to determine the source of infection and mode of transmission of the shigellosis outbreak on March 27, 1998 at a primary school in Taegu city.
METHODS
On-site interview using a standard questionnaire and rectal swab were conducted to 1,629 peoples who ate lunch on March 26 and 1,389 peoples who contacted with suspected cases. And bacteriological examination for 91 environmental materials and 25 food items were performed.
RESULTS
Of the 1,629 persons who ate lunch on March 26, seventy three had culture-confirmed S. sonnei infection(first attack rate: 4.5%). And additional fifty four had shigellosis among those 1,389 persons who might be exposed to the suspected cases(second attack rate: 3.9%). A total of 730 persons who complained one of four typical symptoms or more were treated as suspected cases(first attack rate of suspected cases: 44.8%). S. sonnei was never isolated from water, foods, and other environmental materials. The median incubation period was estimated about two days. The common symptom reported were diarrhea(88.7%), fever(73.4%), abdominal pain(54.7%), and vomiting episode(38.4%) in order. The shorter duration of the outbreak and the large proportion of cases involving students who ate lunch on March 26 are consistent with fecal-oral transmission, although the limited epidemiologic data obtainable do not clearly define the route of transmission.
CONCLUSIONS
Thus the outbreak reported here appear to be related to the unsanitary conditions of food facility in this school.; Summary

An Epidemiological Investigation of Bacterial Dysentery Outbreak in Busan(Pusan), 1999.: Hai Rim Shin, Duk Hee Lee, Heung Man Sul, Sang Won Lee, Young Ju Huh; Korean J Epidemiol. 2000;22(2):93-100.

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BACKGROUND
In March 1999, six children who attended a nursery school became ill with acute gastroenteritis by Shigella sonnei. The majority of the children became sick one day after sharing a snack which was served from one of the children's home. By the time the outbreak of dysentery was recognized, the rest of family members of the children became also sick. The nursery school was located in a crowded residential area. EPIDEMIOLOGIC INVESTIGATION: After active and passive surveillance was established on patients with diarrhea, 438 patients were registered. Among them, 252 patients were considered to have simple diarrhea, but the rest (186 patients) suffered from more than three consecutive diarrheas. Shigella sonnei was isolated from 75 patients. The first attack rate was estimated at 50.0%, the second, 25.6%-34.3% and the third, 13.5%. The epidemic lasted for two months spreading further from person to person in the highly populous area. The active surveillance was implemented after the occurrence of the secondary attack of dysentery among the residents, who had no obvious direct contact with people associated with the nursery school.
CONCLUSION
This investigation demonstrates the need for prompt implementation of active surveillance when Shigella infection is recognized in a highly populous city.; Summary

An Epidemiologic Investigation on the Mode of Transmission of the Lethal Salmonellosis Outbreak in Hamyang County.: Jang Rak Kim, Sang Won Lee, Hong Bin Kim, Jin Cha, Kwang Hyun Lee, Kang Woo Bae; Korean J Epidemiol. 1999;21(2):185-194.

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An outbreak of Salmonella enteritidis epidemic involving about 200 inpatients of gastroenteritis and 1 death occurred among about 750 participants from Hamyang County who attended 4 wedding lunch parties at one buffet restaurant on April 25, 1999. There were also many patients including 1 death among about 500 participants outside Hamyang County who attended same parties. Person to person interviews made to 155 inpatients revealed that distribution of incubation periods was between 1 to 34 hours with median time, 13-14 hours. A retrospective cohort study was conducted to investigate the mode of transmission. Telephone interviews were made to party participants (except 61 inpatients who already had been interviewed personally) on symptoms and on which they had eaten among 40 served foods including water at the parties and data among 288 persons were available for the analyses. One hundred and ninety one interviewees had more than two symptoms among symptoms of diarrhea(more than 3 times), abdominal pain, and fever, which gave an attack rate of 66.3%(191/288). The relative short incubation period and high attack rate suggested the presence of higher infecting dose in this epidemic. Logistic regression analysis revealed that the probable infective foods were boiled cockle, gamju, boiled midodok, fried rices, eomook, and boiled pig's trotter. Salmonella enteritidis were identified in the specimens of boiled cockle, cooked beef, and uncooked beef. Only boiled cockle was both an epidemiological and microbiological infective food. There might be cross-contaminations between several served foods, which meant presence of many contaminated foods by Salmonella enteritidis with different stage of their multiplications. Efforts to inspect food service areas and educate foodhandlers in good personal hygiene and proper foodhandling practices should be strengthened to reduce the incidences of salmonellosis in Korea.; Summary

An Epidemiologic Investigation of Typhoid Fever Outbreak in Pusan, 1996.: Hai Rim Shin, Byung Seong Suh, Jue Bok Song, Duk Hee Lee, Meang Bok Lee, Jin Hyung Park, Man Su Kim, Young Hack Shin, Sang Won Lee, Hee Choul Ohrr; Korean J Epidemiol. 1997;19(2):122-130.

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Abstract PDF: Abstract
An epidemiologic investigation was carried out to identify the source of infection of typhoid fever outbreak, which was occurred in Nam-Gu, Pusan city from April 20 to June 28, 1996. The distribution of 83 reported cases (55 confirmed cases and 28 suspected cases) by sex and age group showed that this epidemic would be occurred by the exposure to a common source with low toxic pathogen because 55.4% of cases were under 20 years old and most of the adults cases were female. The epidemic curve showed a unimodel curve with a peak on about 15 May and tailed down to 23 June, suggesting that the exposure was constant. These results supposed that the contamination of a public water supply would be the source of infection. The analysis of reported cases and population survey conducted to household members and community contacts living in the epidemic area, led the conclusion that the source of infection was tap water supplied through the Dae Youn pumping station, based on the following findings: (1) There were singificant differences of incidence rate among regions (Tong) even though in the same Dong and the spot map of incident cases distributed in accord with the water supply by Dae-Youn pumping station. (2) Among reported cases, 21 cases, including 17 confirmed cases, stated they had used only tap water. (3) The analysis of tap water from the house which had seven typhoid cases, revealed the contamination of E coli and the dilution of residual chlorinated concentration. (4) The outbreak of typhoid fever was stopped after the replacement of The worn-out pipe line of tap water supply to the new one.; Summary

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