Following reports of patients with unexplained pneumonia at the end of December 2019 in Wuhan, China, the causative agent was identified as coronavirus (SARS-CoV-2), and the 2019 novel coronavirus disease was named COVID-19 by the World Health Organization. Putative patients with COVID-19 have been identified in South Korea, and attempts have been made to isolate the pathogen from these patients. Upper and lower respiratory tract secretion samples from putative patients with COVID-19 were inoculated onto cells to isolate the virus. Full genome sequencing and electron microscopy were used to identify the virus. The virus replicated in Vero cells and cytopathic effects were observed. Full genome sequencing showed that the virus genome exhibited sequence homology of more than 99.9% with SARS-CoV-2 which was isolated from patients from other countries, for instance China. Sequence homology of SARS-CoV-2 with SARS-CoV, and MERS-CoV was 77.5% and 50%, respectively. Coronavirus-specific morphology was observed by electron microscopy in virus-infected Vero cells. SARS-CoV-2 was isolated from putative patients with unexplained pneumonia and intermittent coughing and fever. The isolated virus was named BetaCoV/Korea/KCDC03/2020.

Kim JY, et al. J Korean Med Sci. 2019 Dec;35(7):e86. https://doi.org/10.3346/jkms.2020.35.e86

Alveolar macrophages constitutively reside in the respiratory tracts of pigs and humans. An in vivo role of alveolar macrophages in defending against influenza viruses in mice infected with a reassorted influenza virus, 1918 HA/NA:Tx/91, was reported, but there has been no report on an in vivo role of alveolar macrophages in a natural host such as a pig using currently circulating human influenza virus. Here we show that in vivo depletion of alveolar macrophages in pigs by dichloromethylene diphosphonate (MDPCL2) treatment results in 40% mortality when pigs are infected with currently circulating human H1N1 influenza viruses, while none of the infected control pigs died. All infected pigs depleted of alveolar macrophages suffered from more severe respiratory signs than infected control pigs. Induction of tumor necrosis factor alpha in the infected pigs depleted of alveolar macrophages was significantly lower than that in the lungs of infected control pigs, and the induction of interleukin-10, an immunosuppressive cytokine, significantly increased in the lungs of infected pigs depleted of alveolar macrophages compared to infected control pigs. When we measured antibody titers and CD8 ⁺ T lymphocytes expressing gamma interferon (IFN-γ), lower antibody titers and a lower percentage of CD8 ⁺ T lymphocytes expressing IFN-γ were detectable in MDPCL2-treated infected pigs than in phosphate-buffered saline- and liposome-treated and infected pigs. Taken together, our findings suggest that alveolar macrophages are essential for controlling H1N1 influenza viruses in pigs.

Coronavirus Disease-19 (COVID-19) is a respiratory infection characterized by the main symptoms of pneumonia and fever. It is caused by the novel coronavirus severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), which is known to spread via respiratory droplets. We aimed to determine the rate and likelihood of SARS-CoV-2 transmission from COVID-19 patients through non-respiratory routes. Serum, urine, and stool samples were collected from 74 hospitalized patients diagnosed with COVID-19 based on the detection of SARS-CoV-2 in respiratory samples. The SARS-CoV-2 RNA genome was extracted from each specimen and real-time reverse transcription polymerase chain reaction performed. CaCo-2 cells were inoculated with the specimens containing the SARS-COV-2 genome, and subcultured for virus isolation. After culturing, viral replication in the cell supernatant was assessed. Of the samples collected from 74 COVID-19 patients, SARS-CoV-2 was detected in 15 serum, urine, or stool samples. The virus detection rate in the serum, urine, and stool samples were 2.8% (9/323), 0.8% (2/247), and 10.1% (13/129), and the mean viral load was 1,210 ± 1,861, 79 ± 30, and 3,176 ± 7,208 copy/μL, respectively. However, the SARS-CoV-2 was not isolated by the culture method from the samples that tested positive for the SARS-CoV-2 gene. While the virus remained detectable in the respiratory samples of COVID-19 patients for several days after hospitalization, its detection in the serum, urine, and stool samples was intermittent. Since the virus could not be isolated from the SARS-COV-2-positive samples, the risk of viral transmission via stool and urine is expected to be low.

Background: After the detection of the first case of coronavirus disease 2019 (COVID‐19) in South Korea on January 20, 2019, it has triggered three major outbreaks. To decrease the disease burden of COVID‐19, social distancing and active mask wearing were encouraged, reducing the number of patients with influenza‐like illness and altering the detection rate of influenza and respiratory viruses in the Korea Influenza and Respiratory Viruses Surveillance System (KINRESS). We examined the changes in respiratory viruses due to COVID‐19 in South Korea and virological causes of the high detection rate of human rhinovirus (hRV) in 2020.Methods: We collected 52 684 oropharyngeal or nasopharyngeal swab samples from patients with influenza‐like illness in cooperation with KINRESS from 2016 to 2020. Influenza virus and other respiratory viruses were confirmed using real‐time RT‐PCR. The weekly detection rate was used to compare virus detection patterns.Results: Non‐enveloped virus (hRV, human bocavirus, and human adenovirus) detection rates during the COVID‐19 pandemic were maintained. The detection rate of hRV significantly increased in 2020 compared with that in 2019 and was negatively correlated with number of COVID‐19‐confirmed cases in 2020. The distribution of strains and genetic characteristics in hRV did not differ between 2019 and 2020.Conclusions: The COVID‐19 pandemic impacted the respiratory virus detection rate. The extremely low detection rate of enveloped viruses resulted from efforts to prevent the spread of COVID‐19 in South Korea. The high detection rate of hRV may be related to resistance against environmental conditions as a non‐enveloped virus and the long period of viral shedding from patients.

An outbreak of nosocomial infections with Middle East respiratory syndrome coronavirus occurred in South Korea in May 2015. Spike glycoprotein genes of virus strains from South Korea were closely related to those of strains from Riyadh, Saudi Arabia. However, virus strains from South Korea showed strain-specific variations.