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Contact tracing data of SARS-CoV-2 Omicron variant cases during December 2021 in Cantabria, Spain, showed increased transmission (secondary attack rate 39%) compared with Delta cases (secondary attack rate 26%), uninfluenced by vaccination status. Incubation and serial interval periods were also reduced. Half of Omicron transmissions happened before symptom onset in the index case-patient.

In a cohort of essential workers in the United States previously infected with SARS-CoV-2, risk factors for reinfection included being unvaccinated, infrequent mask use, time since first infection, and being non-Hispanic Black. Protecting workers from reinfection requires a multipronged approach including up-to-date vaccination, mask use as recommended, and reduction in underlying health disparities.

Wastewater monitoring of SARS-CoV-2 enables early detection and monitoring of the COVID-19 disease burden in communities and can track specific variants of concern. We determined proportions of the Omicron and Delta variants across 30 municipalities covering >75% of the province of Alberta (population 4.5 million), Canada, during November 2021-January 2022. Larger cities Calgary and Edmonton exhibited more rapid emergence of Omicron than did smaller and more remote municipalities. Notable exceptions were Banff, a small international resort town, and Fort McMurray, a medium-sized northern community that has many workers who fly in and out regularly. The integrated wastewater signal revealed that the Omicron variant represented close to 100% of SARS-CoV-2 burden by late December, before the peak in newly diagnosed clinical cases throughout Alberta in mid-January. These findings demonstrate that wastewater monitoring offers early and reliable population-level results for establishing the extent and spread of SARS-CoV-2 variants.

Empirical evidence on the epidemiological characteristics of the emerged SARS‐CoV‐2 variants could shed light on the transmission potential of the virus and strategic outbreak control planning. In this study, by using contact tracing data collected during an Omicron‐predominant epidemic phase in Hong Kong, we estimated the mean serial interval of SARS‐CoV‐2 Omicron BA.4, BA.5, and BA.2.12.1 variants at 2.8 days (95% credible interval [CrI]: 1.5, 6.7), 2.7 days (95% CrI: 2.1, 3.6), and 4.4 days (95% CrI: 2.6, 7.5), respectively, with adjustment for right truncation and sampling bias. The short serial interval for the current circulating variant indicated that outbreak mitigations through contact tracing and case isolation would be quite challenging.

Background Respiratory viral infections have significant global health impacts. We compared 30‐day intensive care unit (ICU) admission and all‐cause mortality risks in patients with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) Delta and Omicron variants versus influenza A and B (A/B). Methods Data from two retrospective inpatient cohorts in Copenhagen were analyzed. Cohorts included hospitalized influenza A/B patients (2017–2018) and SARS‐CoV‐2 Delta/Omicron patients (2021–2022), aged ≥18 years, admitted within 14 days of a positive real‐time polymerase chain reaction test result. Cumulative ICU admission and mortality rates were estimated using the Aalen–Johansen estimator. Cox regression models calculated hazard ratios (HRs) for ICU admission and mortality. Results The study encompassed 1459 inpatients (Delta: 49%; Omicron: 26%; influenza A: 6.4%; and influenza B: 18%). Cumulative incidence of ICU admission was 11%, 4.0%, 7.5%, and 4.1%, for Delta, Omicron, influenza A, and B, respectively. For ICU admission, adjusted HRs (aHRs) were 3.1 (p < .001) and 1.5 (p = .34) for Delta and Omicron versus influenza B, and 1.5 (p = .36) and 0.71 (p = .48) versus influenza A. For mortality, aHRs were 3.8 (p < .001) and 3.4 (p < .001) for Delta and Omicron versus influenza B, and 2.1 (p = .04) and 1.9 (p = .11) versus influenza A. Conclusion Delta but not Omicron inpatients had an increased risk for ICU admission compared to influenza B; however, both variants were associated with higher risks of mortality than influenza B. Only Delta inpatients had a higher risk of mortality than influenza A inpatients. This study compared the risks of intensive care unit (ICU) admission and mortality among patients with severe acute respiratory syndrome coronavirus 2 Delta and Omicron variants versus those with influenza A and B. It found that patients with the Delta variant had a higher risk of ICU admission and mortality compared to those with influenza B, and a higher mortality risk than those with influenza A. However, while Omicron patients also had a higher mortality risk than influenza B patients, they did not show an increased risk for ICU admission compared to influenza B.

Objective The emergence of SARS‐CoV‐2 infection in dogs and cats in different countries worldwide raises concerns that pets are at a higher risk for spreading or transmitting of SARS‐CoV‐2 to humans and other pets and increased the research works about the zoonotic aspects and natural routes of infection in companion animals. The current study aimed to detect the SARS‐CoV‐2 in household dogs and cats living with COVID‐19 positive owners. Methods Deep oropharyngeal and rectal swabs were collected from 30 household pets (20 cats and 10 dogs) living with COVID‐19 positive owners from April 2021 to 2022 in Kerman, Iran. All dogs’ and cats’ samples were tested by real‐time reverse transcription polymerase chain reaction for detection of SARS‐CoV‐2. Results Two household cats out of 20 examined (10%) were positive for SARS‐CoV‐2, whereas none of the examined dogs were positive for SARS‐CoV‐2. The two cats positive for SARS‐CoV‐2 were symptomatic and suffered from severe anorexia with maximum contact with their infected owners. Conclusion This study reported the presence of SARS‐CoV‐2 in household cats in close contact with COVID‐19 positive owners during the circulation of new SARS‐CoV‐2 variants (Delta and Omicron) in Iran and suggested that the transmission may have occurred from owners to their cats. Therefore, infected owners should eagerly limit close contact with their pets during COVID‐19 illness. • SARS‐CoV‐2 was detected in 2 cats out of 20 examined (10%). • SARS‐CoV‐2 was not detected in dog samples. • The two cats positive for SARS‐CoV‐2 had clinical signs and were in close contact with COVID‐19 positive owners.

COVID-19 is a new acute respiratory infectious disease caused by a novel Coronavirus (2019-COV-2) infection. On November 26, 2021, the World Health Organization announced a new 2019-COV-2 variant strain Omicron (B.1.1.529). Omicron's emergence added further uncertainty to the outbreak. Here we report the first case infected with Omicron in China, a 17-year-old female student. In this paper, the clinical symptoms, laboratory and imaging examinations and treatment of the first Omicron-infected patient in China were analyzed. This report might provide a reference for the diagnosis and treatment of patients infected with Omicron strain across the world. The novel Coronavirus antibody tests were performed on the day of admission: IgM level was normal, novel Coronavirus antibody IgG was 132.666s /CO and IgG was 148.47s /CO on the 7th day of admission. IgG showed an increasing trend, which is consistent with the results of multiple novel Coronavirus non-Omicron strain infections.

With the spread of the Coronavirus disease 2019 (COVID-19), missing learning opportunities due to COVID-19 has been raised as a major concern for university education. We aimed to examine the effectiveness of a booster dose of COVID-19 vaccines among Japanese university students during the spread of the Omicron variant. We enrolled 249 students who became a close contact and 294 COVID-19-infected students though the Hiroshima University COVID-19 registration system. Infection rates of people in close contact with sick individuals and symptoms of infected students were examined. Close contacts who had received a booster dose showed a significantly lower infection rate (31%) compared with those with two doses (50%, p = 0.02) and the unvaccinated (71%, p = 0.002). Age- and sex-adjusted odds ratios of receipt of a booster dose vs. two doses and unvaccinated were 0.40 (95% confidence interval [CI], 0.23–0.70, p = 0.001) and 0.44 (95% CI, 0.25–0.77, p = 0.004), respectively. The incidence of severe fever (38.5°C or higher) was significantly less prevalent in those with a booster dose (16%) compared with two doses (40%, p = 0.002) and those who were unvaccinated (75%, p < 0.0001). Booster doses reduced infection rates among close-contact students and can help students to avoid missing learning opportunities.

Several measures, including behavioral restrictions for individuals, have been taken throughout the world to control the spread of COVID-19. The aim of these measures is to prevent infected persons from coming into contact with susceptible persons. Since the behavioral restrictions for all citizens, such as city-wide lockdowns, were directly linked to the stagnation of economic activities, the assessment of such measures is crucial. In order to evaluate the effects of behavioral restrictions, we employed the broken-link model to compare the situation of COVID-19 in Shanghai, where a lockdown was implemented from March to June 2022, with the situation in Taiwan, where the spread of COVID-19 has been well controlled so far. The results show that the small link-connection probability was achieved by the substantial isolation of infected persons, including the lockdown measures. Although the strict measures for behavioral restrictions were effective to reduce the total number infected people, the daily reported cases per one million people followed the curve evaluated by the broken-link model. This result considers that infections are unavoidable for the population.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019, which has been a global pandemic. Since SARS-CoV-2 is transmitted through contaminated surfaces and aerosols, environmental disinfection is important to block the spread of the virus. Photocatalysts are attractive tools for virus inactivation and are widely used as air purifiers and coating materials. However, photocatalysts are inactive in the dark, and some of them need to be excited with light of a specific wavelength. Therefore, photocatalysts that can effectively inactivate SARS-CoV-2 in indoor environments are needed. Here, we show that a WO3 photocatalyst containing copper inactivated the SARS-CoV-2 WK-521 strain (Pango lineage A) upon irradiation with white light in a time- and concentration-dependent manner. Additionally, this photocatalyst also inactivated SARS-CoV-2 in dark conditions due to the antiviral effect of copper. Furthermore, this photocatalyst inactivated not only the WK-521 strain but also the Omicron variant BA.2. These results indicate that the WO3 photocatalyst containing copper can inactivate indoor SARS-CoV-2 regardless of the variant, in visible light or darkness, making it an effective tool for controlling the spread of SARS-CoV-2.