Epidemiological characteristics of varicella outbreaks in the Republic of Korea, 2016-2020.

OBJECTIVES: We described the trends and epidemiological characteristics of varicella outbreaks from 2016 to 2020 in the Republic of Korea. METHODS: We investigated variables such as the outbreak setting, age of patients, vaccination status, and lesion count. The collected data were analyzed with the Cochrane-Armitage trend test and Kruskal-Wallis test. These statistical tests were performed using R ver. 4.0.3. RESULTS: The number of varicella outbreaks increased from 2016 to 2018; however, after a slight decrease in the number of outbreaks in 2019, the number fell sharply in 2020. The median size of outbreaks decreased from 8 to 9 cases during 2016-2019 to 6 cases in 2020. The median duration of outbreaks was 18 days during 2016-2017, 28 days in 2018, 29 days in 2019, and 15 days in 2020. Varicella outbreaks occurred most frequently in elementary schools, and vaccination coverage of patients increased from 89.4% in 2016 to 97.2% in 2019. The median age of patients with outbreak-related varicella decreased from 8 years in 2016 to 6 years in 2020. CONCLUSION: Significant changes were observed in the age of patients with outbreak-related varicella. Ongoing monitoring of varicella outbreaks should be conducted. Further research will be needed to measure the disease burden of varicella and enable evidence-based policy decisions.

Viral Shedding among Re-Positive Severe Acute Respiratory Syndrome Coronavirus-2 Positive Individuals in Republic of Korea.

This study investigated the infectivity of severe acute respiratory syndrome (SARS-CoV-2) in individuals who re-tested positive for SARS-CoV-2 RNA after recovering from their primary illness. We investigated 295 individuals with re-positive SARS-CoV-2 polymerase chain reaction (PCR) test results and 836 of their close contacts. We attempted virus isolation in individuals with re-positive SARS-CoV-2 PCR test results using cell culture and confirmed the presence of neutralizing antibodies using serological tests. Viral culture was negative in all 108 individuals with re-positive SARS-CoV-2 PCR test results in whom viral culture was performed. Three new cases of SARS-CoV-2 infection were identified among household contacts using PCR. Two of the three new cases had had contact with the index patient during their primary illness, and all three had antibody evidence of past infection. Thus, there was no laboratory evidence of viral shedding and no epidemiological evidence of transmission among individuals with re-positive SARS-CoV-2 PCR test results.

Reports of anaphylaxis after coronavirus disease 2019 vaccination, South Korea, 26 February to 30 April 2021.

The South Korea mass vaccination programme administered 3.8 million doses of COVID-19 vaccinations between 26 February and 30 April 2021. After 173 suspected anaphylaxis reports to the nationwide monitoring system for adverse events following immunisation, 44 anaphylaxis cases were confirmed using Brighton Collaboration case definitions. The rates per million doses were 18.2 cases and 6.2 cases for Vaxzevria and Comirnaty, respectively. Median time of onset was 14 min after vaccination and most cases had recovered at the time of review.

Contact Tracing during Coronavirus Disease Outbreak, South Korea, 2020.

We analyzed reports for 59,073 contacts of 5,706 coronavirus disease (COVID-19) index patients reported in South Korea during January 20-March 27, 2020. Of 10,592 household contacts, 11.8% had COVID-19. Of 48,481 nonhousehold contacts, 1.9% had COVID-19. Use of personal protective measures and social distancing reduces the likelihood of transmission.

Epidemiological Investigation of the Outbreak of Acute Respiratory Infection caused by Adenovirus Type B55 in a Physical Education School in 2017.

BACKGROUND: On May 19, 2017, the cluster of 6 acute respiratory infections due to adenovirus in the swimming department of a physical education school (School J) was reported to Korea Centers for Disease Control and Prevention. An epidemiological investigation was conducted to identify the transmission route of the infection and to control the outbreak. MATERIALS AND METHODS: A retrospective cohort study (Study 1) was conducted on students and teachers of the athletic departments using the swimming pool, and a prospective surveillance (Study 2) was conducted on all students and teachers of the School J. A case was defined as any student and school personnel who developed more than two of the following symptoms from April 10 to July 2, 2017: fever, sore throat, cough, rhinorrhea, or headache. Relative risks (RRs) were calculated to compare the attack rates according to potential risk factors. Multivariable logistic regression was performed to identify the risk factors for infection in the outbreak. RESULTS: 47 cases were identified: 33 (55.9%) cases occurred among 59 students and teachers in Study 1 and 14 (3.9%) among 362 students and school personnel in Study 2. There were 18 laboratory confirmed adenovirus infection cases. The common symptoms were headache (71.7%), fever (69.6%), rhinorrhea (63.0%), sputum (56.5%), and sore throat (54.3%). 23.9% of the cases were accompanied with diarrhea and 19.6% with eye congestion. None of the cases developed pneumonia. 32.6% of the cases were hospitalized. In Study 1, attack rate in the swimming department was higher than that in others (RR: 1.90; 95% confidence interval [CI]: 1.01-3.60). In Study 2, being a member of the shooting department (RR: 20.70; 95% CI: 4.90-87.47) and being a first year high school student (RR: 10.95; 95% CI: 2.90-41.33) were identified as risk factors for the infections. Genetic analyses of the adenoviruses showed 100% identical sequence in homology and confirmed the human adenovirus B55 (HAdV-B55). No adenovirus was detected at examining the water and environment of the swimming pool and dormitory. CONCLUSION: The outbreak is inferred to be occurred via propagated transmission among the students in the same athletic department, while the students with symptoms of respiratory infection continued performing school activities without any restrictions. Infection control measures such as early detection of symptoms of respiratory infection and restriction of group activity are necessary to prevent respiratory infection outbreak in the communal living setting.