Monitoring SARS-CoV-2 variant transitions using differences in diagnostic cycle threshold values of target genes (preprint)

Monitoring the emergence of new SARS-CoV-2 variants is important to detect potential risks of increased transmission or disease severity. We investigated the identification of SARS-CoV-2 variants from real-time reverse transcriptase polymerase chain reaction (RT-PCR) routine diagnostics data. Cycle threshold (Ct) values of positive samples were collected from April 2021 to January 2022 in the Northern Metropolitan Area of Barcelona (n = 15,254). Viral lineage identification from whole-genome sequencing (WGS) was available for 4,618 (30.3%) of these samples. Pairwise differences in the Ct values between gene targets (ΔCt) were analyzed for variants of concern or interest circulating in our area. A specific delay in the Ct of the N-gene compared to the RdRp-gene (ΔCtNR) was observed for Alpha, Delta, Eta and Omicron. Temporal differences in ΔCtNR correlated with the dynamics of viral replacement of Alpha by Delta and of Delta by Omicron according to WGS results. Using ΔCtNR, prediction of new variants of concern at early stages of circulation was achieved with high sensitivity and specificity (91.1% and 97.8% for Delta; 98.5% and 90.8% for Omicron). Thus, tracking population-wide trends in ΔCt values obtained from routine diagnostics testing in combination with WGS could be useful for real-time management and response to local epidemics.

The first wave of the Spanish COVID-19 epidemic was associated with early introductions and fast spread of a dominating genetic variant (preprint)

The COVID-19 pandemic has shaken the world since the beginning of 2020. Spain is among the European countries with the highest incidence of the disease during the first pandemic wave. We established a multidisciplinar consortium to monitor and study the evolution of the epidemic, with the aim of contributing to decision making and stopping rapid spreading across the country. We present the results for 2170 sequences from the first wave of the SARS-Cov-2 epidemic in Spain and representing 12% of diagnosed cases until 14th March. This effort allows us to document at least 500 initial introductions, between early February-March from multiple international sources. Importantly, we document the early raise of two dominant genetic variants in Spain (Spanish Epidemic Clades), named SEC7 and SEC8, likely amplified by superspreading events. In sharp contrast to other non-Asian countries those two variants were closely related to the initial variants of SARS-CoV-2 described in Asia and represented 40% of the genome sequences analyzed. The two dominant SECs were widely spread across the country compared to other genetic variants with SEC8 reaching a 60% prevalence just before the lockdown. Employing Bayesian phylodynamic analysis, we inferred a reduction in the effective reproductive number of these two SECs from around 2.5 to below 0.5 after the implementation of strict public-health interventions in mid March. The effects of lockdown on the genetic variants of the virus are reflected in the general replacement of preexisting SECs by a new variant at the beginning of the summer season. Our results reveal a significant difference in the genetic makeup of the epidemic in Spain and support the effectiveness of lockdown measures in controlling virus spread even for the most successful genetic variants. Finally, earlier control of SEC7 and particularly SEC8 might have reduced the incidence and impact of COVID-19 in our country.

The impact of the COVID-19 pandemic on harm reduction services in Spain (preprint)

Background: Containment policies and other restrictions introduced by the Spanish government in response to the COVID-19 pandemic present challenges for marginalised populations, such as people who use drugs. Harm reduction centres are often linked to social services, mental health services, and infectious disease testing, in addition to tools and services that help to reduce the harms associated with injecting drugs. This study aimed to explore the impact of the pandemic on these services in four autonomous communities in Spain. Methods: : This is a cross-sectional study that employed a seven-section structured survey administered electronically to 20 centres in July 2020. Data from the most heavily affected months (March–June) in 2020 were compared to data from the same period in 2019. Averages were calculated with their ranges, rates, and absolute numbers. Results: : All 11 responding centres reported having had to adapt or modify their services during the Spanish state of alarm (14 March–21 June 2020). One centre reported complete closure for two months and four reported increases in their operating hours. The average number of service users across all centres decreased by 22% in comparison to the same period in the previous year and the average needle distribution decreased by 40% in comparison to 2019. Most centres reported a decrease in infectious disease testing rates (hepatitis B and C viruses [HBV, HCV], human immunodeficiency virus (HIV), and tuberculosis [TB]) for March, April, and May in 2020 compared to the previous year. Reported deaths as a result of overdose did not increase during the state of alarm, but 2/11 (18%) centres reported an increase in overdose deaths immediately after finalisation of the state of alarm. Conclusion: Overall, Spanish harm reduction centres were able to continue operating and offering services by adjusting operating hours. The number of overall service users and needles distributed fell during the Spanish state of alarm lockdown period, suggesting that fewer clients accessed harm reduction services during this time, putting them at greater risk of reusing or sharing injecting equipment, overdosing, acquiring infectious diseases with decreased access to testing or discontinuing ongoing treatment such as methadone maintenance therapy, hepatitis C treatment, or antiretroviral therapy.