The emergence of the COVID-19 pandemic has led to significant progress in the field of wastewater-based surveillance (WBS) of respiratory pathogens and highlighted its potential for a wider application in public health surveillance. This study aimed to evaluate whether monitoring of respiratory syncytial virus (RSV) in wastewater can provide a comprehensive picture of disease transmission at the community level. The study was conducted in Larissa (Central Greece) between October 2022 and January 2023. Forty-six wastewater samples were collected from the inlet of the wastewater treatment plant of Larissa and analyzed with a real-time reverse transcription polymerase chain reaction (RT-PCR) based method. RSV and SARS-CoV-2 wastewater viral loads (genome copies/100,000 inhabitants) were analyzed against sentinel surveillance data on influenza-like illness (ILI) to identify potential associations. Univariate linear regression analysis revealed that RSV wastewater viral load (lagged by one week) and ILI notification rates in children up to 14 years old were strongly associated (std. Beta: 0.73 (95% CI: 0.31–1.14), p = 0.002, R2 = 0.308). A weaker association was found between SARS-CoV-2 viral load and ILI rates in the 15+ age group (std. Beta: 0.56 (95% CI: 0.06–1.05), p = 0.032, R2 = 0.527). The results support the incorporation of RSV monitoring into existing wastewater-based surveillance systems.
Early identification of COVID-19 cases has been vital for reducing transmission and enabling treatment. In Greece, in autumn 2021 when Delta was the predominant circulating variant, unvaccinated citizens had to be tested before attending activities, and self-testing was required twice a week for students (5–17 years). Here, we describe the time of diagnosis by age group and possible exposure to assess testing strategies (September to November 2021). Information on the presence of symptoms at the time of diagnosis was available for 69,298 cases; 24,855 (36%) were asymptomatic or tested the same day as onset (early diagnosis), 21,310 (31%) reported testing one day after, and 23,133 (33%) did so two or more days after the onset of symptoms. The median lag was 2 days (1–14). Early diagnosis significantly differed among age groups (p-value < 0.001) and was higher among children. For every one-year increase of age, the odds of an early diagnosis were reduced by 1%. Cases exposed during training activities or in settings such as accommodation centers and hospitals were more frequently diagnosed early. The percentage of persons having a positive self-test before a rapid test/PCR diagnosis ranged from 7% in the age group of 60 years and above to 86% in the age group of 5–17 years. The provision of self-tests in schools and increased testing in closed settings led to an earlier diagnosis and probably to a decreased transmission of the virus in the period during which Delta was the predominant variant in Greece. However, more effort is needed for early diagnosis of adults in the community, especially after the onset of symptoms.
Background The emergence of the highly infectious Omicron variant at the end of 2021 changed the pandemic dynamics, also causing an increase in COVID-19 re-infections. Our aim was to investigate suspected re-infections and the characteristics of individuals with multiple infections since the beginning of the pandemic until early April 2022. Methods Since the beginning of the pandemic, all COVID-19 positive tests (Rapid Antigen Tests - RAT and PCR) have been recorded in the COVID-19 National Electronic Registry. Cases were extracted and reported daily based on the first positive test for each individual (first episodes). Establishment of the Omicron variant, associated with a re-infection surge, triggered the decision for modifying case definition and applying a different methodology to include suspected re-infections in the number of daily reported cases after 3rd of April. Suspected re-infections were defined as “positive PCR or RAT sample ≥90 days following a previous positive PCR or RAT”. The number of re-infections were estimated retrospectively on the Registry’s data. Results Overall, 6,348 suspected re-infections were recorded up to 15/12/2021 (0.6% of the laboratory confirmed tests), whereas until 3/4/22 the number was increased at 115.201, raising the percentage to 4%. Distribution of the number of reinfections per ISO week is depicted in Figure 1, along with the number of first episodes. Suspected re-infections stand for 3.7% of the total number of first episodes recorded up to 3/4/22 (3,077,711), with their integration having a noticeable effect on case counting. Among them, 99.3% represent a second episode of infection and 0.7% multiple re-infections. Median age of suspected re-infections was 29 years (IQR: 19-44) (Figure 2). The median length of the time interval between two subsequent infections was 8 months (IQR: 5-12) (Figure 3). Conclusion Up until mid-December 2021, COVID-19 re-infection was uncommon, changing to higher rates after the emergence of Omicron variant, thus documenting the immune escape capacity of this variant. Besides the improvement in surveillance, knowledge about the re-infections and their characteristics provides a proxy of the immune protection from previous exposure to COVID-19, against circulating variants over time. Disclosures All Authors: No reported disclosures.
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