Integrated genomic surveillance enables tracing of person-to-person SARS-CoV-2 transmission chains during community transmission and reveals extensive onward transmission of travel-imported infections, Germany, June to July 2021.

BackgroundTracking person-to-person SARS-CoV-2 transmission in the population is important to understand the epidemiology of community transmission and may contribute to the containment of SARS-CoV-2. Neither contact tracing nor genomic surveillance alone, however, are typically sufficient to achieve this objective.AimWe demonstrate the successful application of the integrated genomic surveillance (IGS) system of the German city of Düsseldorf for tracing SARS-CoV-2 transmission chains in the population as well as detecting and investigating travel-associated SARS-CoV-2 infection clusters.MethodsGenomic surveillance, phylogenetic analysis, and structured case interviews were integrated to elucidate two genetically defined clusters of SARS-CoV-2 isolates detected by IGS in Düsseldorf in July 2021.ResultsCluster 1 (n = 67 Düsseldorf cases) and Cluster 2 (n = 36) were detected in a surveillance dataset of 518 high-quality SARS-CoV-2 genomes from Düsseldorf (53% of total cases, sampled mid-June to July 2021). Cluster 1 could be traced back to a complex pattern of transmission in nightlife venues following a putative importation by a SARS-CoV-2-infected return traveller (IP) in late June; 28 SARS-CoV-2 cases could be epidemiologically directly linked to IP. Supported by viral genome data from Spain, Cluster 2 was shown to represent multiple independent introduction events of a viral strain circulating in Catalonia and other European countries, followed by diffuse community transmission in Düsseldorf.ConclusionIGS enabled high-resolution tracing of SARS-CoV-2 transmission in an internationally connected city during community transmission and provided infection chain-level evidence of the downstream propagation of travel-imported SARS-CoV-2 cases.

Effect of COVID-19 Pandemic on Invasive Pneumococcal Disease in Children, Catalonia, Spain.

We analyzed the effect of COVID-19 on healthcare demand and invasive pneumococcal disease in children in Catalonia, Spain. Compared with 2018-2019, we noted large reductions in healthcare activities and incidence of invasive pneumococcal disease in 2020. These changes likely resulted from nonpharmaceutical measures implemented during the COVID-19 pandemic.

The Catalan Surveillance Network of SARS-CoV-2 in Sewage: design, implementation, and performance.

Wastewater-based epidemiology has shown to be an efficient tool to track the circulation of SARS-CoV-2 in communities assisted by wastewater treatment plants (WWTPs). The challenge comes when this approach is employed to help Health authorities in their decision-making. Here, we describe the roadmap for the design and deployment of SARSAIGUA, the Catalan Surveillance Network of SARS-CoV-2 in Sewage. The network monitors, weekly or biweekly, 56 WWTPs evenly distributed across the territory and serving 6 M inhabitants (80% of the Catalan population). Each week, samples from 45 WWTPs are collected, analyzed, results reported to Health authorities, and finally published within less than 72 h in an online dashboard ( https://sarsaigua.icra.cat ). After 20 months of monitoring (July 20-March 22), the standardized viral load (gene copies/day) in all the WWTPs monitored fairly matched the cumulative number of COVID-19 cases along the successive pandemic waves, showing a good fit with the diagnosed cases in the served municipalities (Spearman Rho = 0.69). Here we describe the roadmap of the design and deployment of SARSAIGUA while providing several open-access tools for the management and visualization of the surveillance data.

SARS-CoV-2 Catalonia contact tracing program: evaluation of key performance indicators.

BACKGROUND: Guidance on SARS-CoV-2 contact tracing indicators have been recently revised by international public health agencies. The aim of the study is to describe and analyse contact tracing indicators based on Catalonia's (Spain) real data and proposing to update them according to recommendations. METHODS: Retrospective cohort analysis including Catalonia's contact tracing dataset from 20 May until 31 December 2020. Descriptive statistics are performed including sociodemographic stratification by age, and differences are assessed over the study period. RESULTS: We analysed 923,072 contacts from 301,522 SARS-CoV-2 cases with identified contacts (67.1% contact tracing coverage). The average number of contacts per case was 4.6 (median 3, range 1-243). A total of 403,377 contacts accepted follow-up through three phone calls over a 14-day quarantine period (84.5% of contacts requiring follow-up). The percentage of new cases declared as contacts 14 days prior to diagnosis evolved from 33.9% in May to 57.9% in November. All indicators significantly improved towards the target over time (p < 0.05 for all four indicators). CONCLUSIONS: Catalonia's SARS-CoV-2 contact tracing indicators improved over time despite challenging context. The critical revision of the indicator's framework aims to provide essential information in control policies, new indicators proposed will improve system delay's follow-up. The study provides information on COVID-19 indicators framework experience from country's real data, allowing to improve monitoring tools in 2021-2022. With the SARS-CoV-2 pandemic being so harmful to health systems and globally, is important to analyse and share contact tracing data with the scientific community.

Surveillance of SARS-CoV-2 virus circulation using Acute Respiratory Infections sentinel system of Catalonia (PIDIRAC) during the 2019-2020 season: A retrospective observational study.

BACKGROUND: In the context of COVID-19 pandemic in Catalonia (Spain), the present study analyses respiratory samples collected by the primary care network using Acute Respiratory Infections Sentinel Surveillance System (PIDIRAC) during the 2019-2020 season to complement the pandemic surveillance system in place to detect SARS-CoV-2. The aim of the study is to describe whether SARS-CoV-2 was circulating before the first confirmed case was detected in Catalonia, on February 25th, 2020. METHODS: The study sample was made up of all samples collected by the PIDIRAC primary care network as part of the Influenza and Acute Respiratory Infections (ARI) surveillance system activities. The study on respiratory virus included coronavirus using multiple RT-PCR assays. All positive samples for human coronavirus were subsequently typed for HKU1, OC43, NL63, 229E. Every respiratory sample was frozen at-80°C and retrospectively studied for SARS-CoV-2 detection. A descriptive study was performed, analysing significant differences among variables related to SARS-CoV- 2 cases comparing with rest of coronaviruses cases through a bivariate study with Chi-squared test and statistical significance at 95%. RESULTS: Between October 2019 and April 2020, 878 respiratory samples from patients with acute respiratory infection or influenza syndrome obtained by PIDIRAC were analysed. 51.9% tested positive for influenza virus, 48.1% for other respiratory viruses. SARS-CoV-2 was present in 6 samples. The first positive SARS-CoV-2 case had symptom onset on 2 March 2020. These 6 cases were 3 men and 3 women, aged between 25 and 50 years old. 67% had risk factors, none had previous travel history nor presented viral coinfection. All of them recovered favourably. CONCLUSION: Sentinel Surveillance PIDIRAC enhances global epidemiological surveillance by allowing confirmation of viral circulation and describes the epidemiology of generalized community respiratory viruses' transmission in Catalonia. The system can provide an alert signal when identification of a virus is not achieved in order to take adequate preparedness measures.

SARS-CoV-2 seroprevalence in blood donors before and after the first wave in Catalonia (Spain).

BACKGROUND: Due to the COVID-19 pandemic, a national lockdown was applied in Spain from March to May 2020. It is uncertain when SARS-CoV-2 started to circulate in Catalonia, and only a few cases were diagnosed in this period. We assessed the SARS-CoV-2 seroprevalence in blood donors before and after the first wave and compared it with public health service (PHS) data. MATERIALS AND METHODS: Retrospective archive or prospective fresh blood samples were obtained from blood donors aged 18 to 70 and anonymized after demographic data had been recorded (gender, age, place of residence, blood collection date). Two CE-marked enzyme-linked immunosorbent assays were used to test for anti-SARS-CoV-2. A SARS-CoV-2 IgM test was additionally performed in positive samples. Individuals aged 18 to 70 from among the general population diagnosed as having SARS-CoV-2 by the PHS were included for comparison with blood donor results. RESULTS: A total of 10,170 blood donations were included in the first period, between 24 February and 9 March 2020, and 6,829 in the second period, between 16 May and 17 June 2020. The observed SARS-CoV-2 seroprevalence among blood donors rose from 0.27% (95% CI: 0.18-0.39) before the first wave to 5.55% (95% CI: 5.03-6.12) after it, and was even higher (6.90% [95% CI: 5.64-8.41]) among blood donors aged 18 to 29. The seroprevalence among blood donors was higher in more populated areas (Barcelona: 7.69%). A comparison of blood donor data with officially diagnosed cases showed a global 87.44% underestimation of SARS-CoV-2 in June 2020. DISCUSSION: We analyzed the explosive 3-month increase in blood donor SARS-CoV-2 seroprevalence (from 0.27% to 5.55%) and show that more than 87% of cases went undiagnosed, despite the unprecedented deployment of testing measures. SARS-CoV-2 IgM results suggest that the virus was circulating among blood donors in February 2020. Blood donors are definitively proven to be a valuable resource for emerging disease surveillance studies.