Impact of COVID-19 and closed transmission of SARS-CoV-2 during the first wave in Toyama Prefecture, Japan, March 30 to May 18, 2020.

We studied 226 patients in Toyama Prefecture, notified with COVID-19 during the first wave between March 30 and May 18, 2020. Of the 226 patients, 22 (9.7%) died, of whom most (95%) were aged ≥65 years. A large cluster comprising 59 patients (41 residents and 18 staff members) was identified in a nursing home on April 17. No deaths occurred among the staff members, but 12 of the 41 cases in residents (29%) died. Although the Ct values were significantly lower in the 20-64 and the ≥65 years age-groups than in the age <20 years age-group, no correlation was found between the Ct values and the severity, fatal outcome, or secondary infection. The haplotype network of 145 SARS-CoV-2 isolates (64%) from 226 patients was analyzed. The viral genomes of the case groups differed by less than five nucleotide bases. These data suggest that SARS-CoV-2 strains, which were initially introduced into Toyama Prefecture during late March and early April 2020, and their closely related strains, identified as the lineage B.1.1, circulated during the first wave. The reduced inter-prefectural mobility of local residents may support a lack of strain diversity in SARS-CoV-2 during a state of emergency in the first wave.

Long-Term Detection and Isolation of Severe Fever with Thrombocytopenia Syndrome (SFTS) Virus in Dog Urine.

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne infection caused by the SFTS virus (SFTSV), with a high fatality rate of approximately 30% in humans. In recent years, cases of contact infection with SFTSV via bodily fluids of infected dogs and cats have been reported. In this study, clinical and virological analyses were performed in two dogs in which SFTSV infection was confirmed for the first time in the Toyama prefecture. Both dogs recovered; however, one was severely ill and the other mildly ill. The amount of the SFTSV gene was reduced to almost similar levels in both dogs. In the dogs' sera, the SFTSV gene was detected at a low level but fell below the detection limit approximately 2 weeks after onset. Notably, the SFTSV gene was detected at levels several thousand times higher in urine than in other specimens from both dogs. Furthermore, the gene was detected in the urine for a long period of >2 months. The clinical signs disappeared on days 1 or 6 after onset, but infectious SFTSV was detected in the urine up to 3 weeks later. Therefore, it is necessary to be careful about contact with bodily fluids, especially urine, even after symptoms have disappeared.

Activation of SARS-CoV-2 by trypsin-like proteases in the clinical specimens of patients with COVID-19.

SARS-CoV-2 enters host cells through the angiotensin converting enzyme 2 (ACE2) receptor and/or transmembrane protease, serine 2 (TMPRSS2). In this study, we investigated whether proteases increased SARS-CoV-2 infectivity using pseudotyped viruses and clinical specimens from patients with COVID-19. First, we investigated how trypsin increased infectivity using the pseudotyped virus. Our findings revealed that trypsin increased infectivity after the virus was adsorbed on the cells, but no increase in infectivity was observed when the virus was treated with trypsin. We examined the effect of trypsin on SARS-CoV-2 infection in clinical specimens and found that the infectivity of the SARS-CoV-2 delta variant increased 36,000-fold after trypsin treatment. By contrast, the infectivity of SARS-CoV-2 omicron variant increased to less than 20-fold in the clinical specimens. Finally, using five clinical specimens containing delta variants, enhancement of viral infectivity was evaluated in the presence of the culture supernatant of several anaerobic bacteria. As a result, viral infectivities of all the clinical specimens containing culture supernatants of Fusobacterium necrophorum were significantly increased from several- to tenfold. Because SARS-CoV-2 infectivity increases in the oral cavity, which may contain anaerobic bacteria, keeping the oral cavities clean may help prevent SARS-CoV-2 infection.

Evaluation of SARS-CoV-2 isolation in cell culture from nasal/nasopharyngeal swabs or saliva specimens of patients with COVID-19.

It has been revealed that SARS-CoV-2 can be efficiently isolated from clinical specimens such as nasal/nasopharyngeal swabs or saliva in cultured cells. In this study, we examined the efficiency of viral isolation including SARS-CoV-2 mutant strains between nasal/nasopharyngeal swab or saliva specimens. Furthermore, we also examined the comparison of viral isolation rates by sample species using simulated specimens for COVID-19. As a result, it was found that the isolation efficiency of SARS-CoV-2 in the saliva specimens was significantly lower than that in the nasal/nasopharyngeal swab specimens. In order to determine which component of saliva is responsible for the lower isolation rate of saliva specimens, we tested the abilities of lactoferrin, amylase, cathelicidin, and mucin, which are considered to be abundant in saliva, to inhibit the infection of SARS-CoV-2 pseudotyped viruses (SARS-CoV-2pv). Lactoferrin and amylase were found to inhibit SARS-CoV-2pv infection. In conclusion, even if the same number of viral genome copies was detected by the real-time RT-PCR test, infection of SARS-CoV-2 present in saliva is thought to be inhibited by inhibitory factors such as lactoferrin and amylase, compared to nasal/nasopharyngeal swab specimens.

Neutralizing Antibody Levels and Epidemiological Characteristics of Patients with Breakthrough COVID-19 Infection in Toyama, Japan.

Breakthrough infection (BI) after coronavirus disease 2019 (COVID-19) vaccination has increased owing to the emergence of novel SARS-CoV-2 variants. In this study, we analyzed the epidemiological information and possession status of neutralizing antibodies in patients with BI using SARS-CoV-2 pseudotyped viruses. Analysis of 44 specimens from patients diagnosed with COVID-19 after two or more vaccinations showed high inhibition of infection by 90% or more against the Wuhan strain and the Alpha and Delta variants of pseudotyped viruses in 40 specimens. In contrast, almost no neutralizing activity was observed against the Omicron BA.1 variant. Many patients without neutralizing activity or BI were immunosuppressed. The results of this study show that contact with an infected person can result in BI, even when there are sufficient neutralizing antibodies in the blood. Thus, sufficient precautions must be taken to prevent infection even after vaccination.

Neutralization of Omicron subvariants BA.1 and BA.5 by a booster dose of COVID-19 mRNA vaccine in a Japanese nursing home cohort.

The sustained epidemic of Omicron subvariants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a worldwide concern, and older adults are at high risk. We conducted a prospective cohort study to assess the immunogenicity of COVID-19 mRNA vaccines (BNT162b2 or mRNA-1273) in nursing home residents and staff between May 2021 and December 2022. A total of 335 SARS-CoV-2 naïve individuals, including 141 residents (median age: 88 years) and 194 staff (median age: 44 years) participated. Receptor-binding domain (RBD) and nucleocapsid (N) protein IgG and neutralizing titer (NT) against the Wuhan strain, Alpha and Delta variants, and Omicron BA.1 and BA.5 subvariants were measured in serum samples drawn from participants after the second and third doses of mRNA vaccine using SARS-CoV-2 pseudotyped virus. Breakthrough infection (BTI) was confirmed by a notification of COVID-19 or a positive anti-N IgG result in serum after mRNA vaccination. Fifty-one participants experienced SARS-CoV-2 BTI during the study period. The RBD IgG and NTs against Omicron BA.1 and BA.5 were markedly increased in SARS CoV-2 naïve participants 2 months after the third dose of mRNA vaccine, compared to those 5 months after the second dose, and declined 5 months after the third dose. The decline in RBD IgG and NT against Omicron BA.1 and BA.5 in SARS-CoV-2 naïve participants after the second and the third dose was particularly marked in those aged ≥ 80 years. BTIs during the BA.5 epidemic period, which occurred between 2 and 5 months after the third dose, induced a robust NT against BA.5 even five months after the booster dose vaccination. Further studies are required to assess the sustainability of NTs elicited by Omicron-containing bivalent mRNA booster vaccine in older adults.

[Depression screening test for patients with metastatic gastric and colorectal cancer].

The prevalence of depression has been reported to be higher in cancer patients, especially those of advanced stage, compared to normal controls. However, depression is often under-recognized in clinical oncology settings. And this psychological problem is not routinely assessed even in patients with inoperable metastatic cancer who often have psychological disorders. Psychological distress including depression, is affected by physical, psychosocial, and clinical factors. In order to detect psychiatric problems at the early stage, we assessed the mental conditions of 47 inpatients with metastatic gastric and colorectal cancerusing the Japanese version of Zung's Self Rating Depression Scale(SDS)and analyzed the relationships between these factors and SDS scores. While SDS scores of our patients did not differ according to their gender, age, performance status (PS), ortypes of patients' character, they were significantly higher in Group B(cancer patients with palliative care alone), compared to Group A(those receiving chemotherapy)(p<0. 001). As the disease in the four identical patients progressed to the terminal stage, their scores were significantly increased, respectively(p<0. 05). These results suggest that psychological intervention should be more critical for terminally ill patients without any indication of chemotherapy.