Role of SARS-CoV-2 mutations in the evolution of the COVID-19 pandemic (preprint)

RNA viruses, including SARS-CoV-2, evolve by mutation acquisition, or by hybridization between viral genomes. The SARS-CoV-2 pandemic provided an exceptional opportunity to analyze the mutations that appeared over a three-year period. In this study, we analysed the type of mutations and their epidemic consequences on the thousands of genomes produced in our laboratory. These were obtained by next-generation sequencing from respiratory samples performed for genomic surveillance. The frequencies of mutations were calculated using Nextclade, Microsoft Excel, and an in-house Python script. In total, 61,397 genomes matching 483 Pangolin lineages were analyzed; 22,225 nucleotide mutations were identified, and of them 220 (1.0%) were each at the root of at least 836 genomes, a frequency threshold classifying mutations as hyperfertile. Two of these seeded the pandemic in Europe, namely a mutation in the RNA-dependent RNA polymerase associated with an increased mutation rate (P323L) and one in the spike protein (D614G), which plays a particular role in virus fitness. Most of these 220 hyperfertile mutations occurred in areas not predicted to be associated with increased virulence. Their number was 8+/-6 (0-22) per 1,000 nucleotides on average per gene. They were 3.7 times more frequent in accessory than informational genes (14 versus 4; p= 0.0037). Particularly, they were 4.1 times more frequent in ORF8 than in the gene encoding RNA polymerase. Interestingly, stop codons were present in 97 positions, almost only in six accessory genes including ORF7a (25 per 100 codons) and ORF8 (21). Furthermore, 1,661 mutations (16.3%) were associated with a lower number of offspring (50-835) and classified as fertile. In conclusion, except for two initial mutations that could predict a change in the dynamics of the epidemic (mutation rate and change in the virus attachment site), most of the hyperfertile mutations did not predict the emergence of a new epidemic form. Significantly, some mutations were in non-coding areas and some consisted of stop codons, indicating that some genes (particularly ORF7a and ORF8) were rather non-virulence genes at a given stage of the epidemic, which is an unusual concept for viruses.

Early Treatment with Hydroxychloroquine and Azithromycin: A Real-Life Monocentric Retrospective Cohort Study of 30,423 COVID-19 Patients (preprint)

Objective To estimate the comparative effectiveness of combination therapy with hydroxychloroquine (HCQ) and azithromycin for coronavirus disease 2019 (COVID-19)-related death based on a large monocentric cohort independent of investigators putative biases in a real-world setting. Design Retrospective monocentric cohort study, with comprehensive data collection authenticated by an external bailiff and death reports from a national database (French National Death Registry). Setting Institut Hospitalo-Universitaire Mediterranee Infection Center in Marseille, France. Participants All adults older than 18 years with PCR-proven COVID-19 who were treated directly in our centre between 2 March 2020 and 31 December 2021 and did not refuse the use of their data. Interventions HCQ and azithromycin (HCQ-AZ) as a reference treatment were compared to other regimens containing HCQ, ivermectin and azithromycin alone, combined, or none of these three drugs. The effect of vaccination was also evaluated. Main outcome measures 6-week all-cause mortality. Multivariable logistic regression estimated treatment effectiveness with adjustments for age, sex, comorbidities, vaccination, period of infection or virus variant, and outpatient or inpatient care. Results Total 30,423 COVID-19 patients were analysed (86 refused the analysis of their data) including 30,202 with available treatment data, and 535 died (1.77%). All-cause mortality was very low among patients < 50 years (8/15,925 (0.05%)) and among outpatients treated with HCQ-AZ (21 deaths out of 21,135 (0.1%), never exceeding 0.2% regardless of epidemic period). HCQ-AZ treatment was associated with a significantly lower mortality rate than no HCQ-AZ after adjustment for sex, age, period and patient care setting (adjusted OR (aOR) 95% confidence interval (CI) 0.55, 0.45-0.68). The effect was greater among outpatients (71% death protection rate) than among inpatients (45%). In a subset of 16,063 patients with available comorbidities and vaccinations status, obesity (2.01, 1.23-3.29), chronic respiratory disease (2.93, 1.29-6.64), and immunodeficiency (4.01, 1.69-9.50), on the one hand, and vaccination (0.29, 0.12-0.67) and HCQ-AZ treatment (0.47, 0.29-0.76), on the other hand, were independent factors associated with mortality. HCQ, alone or in any association, was associated with significant protection from death among outpatients (0.41, 0.21-0.79) and inpatients (0.59, 0.47-0.73). Conclusions HCQ prescribed early or late protects in part from COVID-19-related death. During pandemic health crises, financial stakes are enormous. Authentication of the data by an independent external judicial officer should be required. Public sharing of anonymized databases, ensuring their verifiability, should be mandatory in this context to avoid fake publications.

SARS-CoV-2 quasi-species analysis from patients with persistent nasopharyngeal shedding: potential tool to finest genomic watch (preprint)

At the time of a new and unprecedented viral pandemic, many questions are being asked about the genomic evolution of SARS-CoV-2 and the emergence of different variants, leading to therapeutic and immune evasion and survival of this genetically highly labile RNA virus. The nasopharyngeal persistence of infectious virus beyond 17 days proves its constant interaction with the human immune system and increases the intra-individual mutational possibilities. We performed a prospective high-throughput sequencing study (ARTIC Nanopore) of SARS-CoV-2 from so-called "persistent" patients, comparing them with a non-persistent population, and analyzing the quasi-species present in a single sample at time t. Global intra-individual variability in persistent patients was found to be higher than in controls (mean 5.3%, Standard deviation 0.9 versus 4.6% SD 0.3, respectively, p< 0,001). In the detailed analysis, we found a greater difference between persistent and non-persistent patients with non-severe COVID 19, and between the two groups infected with clade 20A. Furthermore, we found minority N501Y and P681H mutation clouds in all patients, with no significant differences found between both groups. The question of the SARS-CoV-2 viral variants’ genesis remains to be further investigated, with the need to prevent new viral propagations and their consequences, and quasi-species analysis could be an important key to watch out.

A 21L/BA.2-21K/BA.1 MixOmicron SARS-CoV-2 hybrid undetected by qPCR that screen for variant in routine diagnosis (preprint)

Among the multiple SARS-CoV-2 variants identified since summer 2020, several have co-circulated, creating opportunities for coinfections and potentially genetic recombinations that are common in coronaviruses. Viral recombinants are indeed beginning to be reported more frequently. Here, we describe a new SARS-CoV-2 recombinant genome that is mostly that of a Omicron 21L/BA.2 variant but with a 3-prime tip originating from a Omicron 21K/BA.1 variant. Two such genomes were obtained in our institute from adults sampled in February 2022 in university hospitals of Marseille, southern France, by next-generation sequencing carried out with the Illumina or Nanopore technologies. The recombination site was located between nucleotides 26,858-27,382. In the two genomic assemblies, mean sequencing depth at mutation-harboring positions was 271 and 1,362 reads and mean prevalence of the majoritary nucleotide was 99.3+/-2.2% and 98.8+/-1.6%, respectively. Phylogeny generated trees with slightly different topologies according to whether genomes were depleted or not of the 3-prime tip. This 3-prime terminal end brought in the Omicron 21L/BA.2 genome a short transposable element of 41 nucleotides named S2m that is present in most SARS-CoV-2 except a few variants among which the Omicron 21L/BA.2 variant and may be involved in virulence. Importantly, this recombinant is not detected by currently used qPCR that screen for variants in routine diagnosis. The present observation emphasizes the need to survey closely the genetic pathways of SARS-CoV-2 variability by whole genome sequencing, and it could contribute to gain a better understanding of factors that lead to observed differences between epidemic potentials of the different variants.

Sequential appearance and isolation of a SARS-CoV-2 recombinant between two major SARS-CoV-2 variants in a chronically infected immunocompromised patient (preprint)

Genetic recombination is a major evolutionary mechanism among RNA viruses, and it is common in coronaviruses, including those infecting humans. A few SARS-CoV-2 recombinants have been reported to date whose genome harbored combinations of mutations from different mutants or variants, but a single patient sample was analyzed, and the virus was not isolated. Here, we report the gradual creation of a hybrid genome of B.1.160 and Alpha variants in a lymphoma patient chronically infected for 14 months, and we isolated the recombinant virus. The hybrid genome was obtained by next-generation sequencing, and recombination sites were confirmed by PCR. This consisted of a parental B.1.160 backbone interspersed with two fragments, including the spike gene, from an Alpha variant. Analysis of seven sequential samples from the patient decoded the recombination steps, including the initial infection with a B.1.160 variant, then a concurrent infection with this variant and an Alpha variant, the generation of hybrid genomes, and eventually the emergence of a predominant recombinant virus isolated at the end of the patient follow-up. This case exemplifies the recombination process of SARS-CoV-2 in real life, and it calls for intensifying genomic surveillance in patients coinfected with different SARS-CoV-2 variants, and more generally with several RNA viruses, as this may lead to the creation of new viruses.

Culture and identification of a Deltamicron SARS-CoV-2 in a three cases cluster in southern France (preprint)

Multiple SARS-CoV-2 variants have successively, or concommitantly spread worldwide since summer 2020. A few co-infections with different variants were reported and genetic recombinations, common among coronaviruses, were reported or suspected based on co-detection of signature mutations of different variants in a given genome. Here were report three infections in southern France with a Delta 21J/AY.4-Omicron 21K/BA.1 Deltamicron recombinant. The hybrid genome harbors signature mutations of the two lineages, supported by a mean sequencing depth of 1,163-1,421 reads and mean nucleotide diversity of 0.1-0.6%. It is composed of the near full-length spike gene (from codons 156-179) of an Omicron 21K/BA.1 variant in a Delta 21J/AY.4 lineage backbone. It is similar to those reported for 15 other patients sampled since January 2022 in Europe. Importantly, we cultured an isolate of this recombinant and sequenced its genome. It was observed by scanning electron microscopy. As it is misidentified with current variant screening qPCR, we designed and implemented for routine diagnosis a specific duplex qPCR. Finally, structural analysis of the recombinant spike suggested its hybrid content could optimize viral binding to the host cell membrane. These findings prompt further studies of the virological, epidemiological, and clinical features of this recombinant.

First cases of infection with the 21L/BA.2 Omicron variant in Marseille, France (preprint)

The SARS-CoV-2 21K/BA.1, 21L/BA.2, and BA.3 Omicron variants have recently emerged worldwide. To date, the 21L/BA.2 Omicron variant has remained very minority globally but became predominant in Denmark instead of the 21K/BA.1 variant. Here we describe the first cases diagnosed with this variant in south-eastern France. We identified thirteen cases using variant-specific qPCR and next-generation sequencing between 28/11/2021 and 31/01/2022, the first two cases being diagnosed in travellers returning from Tanzania. Overall, viral genomes displayed a mean (+/-standard deviation) number of 65.9+/-2.5 (range, 61-69) nucleotide substitutions and 31.0+/-8.3 (27-50) nucleotide deletions, resulting in 49.6+/-2.2 (45-52) amino acid substitutions (including 28 in the spike protein) and 12.4+/-1.1 (12-15) amino acid deletions. Phylogeny showed the distribution in three different clusters of these genomes, which were most closely related to genomes from England and South Africa, from Singapore and Nepal, or from France and Denmark. Structural predictions pointed out a significant enlargement and flattening of the 21L/BA.2 N-terminal domain surface compared with that of the 21K/BA.2 Omicron variant, which may facilitate initial viral interactions with lipid rafts. Close surveillance is needed at global, country and center scales to monitor the incidence and clinical outcome of the 21L/BA.2 Omicron variant.

The emergence, spread and vanishing of a French SARS-CoV-2 variant exemplifies the fate of RNA virus epidemics and obeys the Black Queen rule (preprint)

Summary The nature and dynamics of mutations associated with the emergence, spread and vanishing of SARS-CoV-2 variants causing successive waves are complex 1-5 . We determined the kinetics of the most common French variant (“Marseille-4”) for 10 months since its onset in July 2020 5 . Here, we analysed and classified into subvariants and lineages 7,453 genomes obtained by next-generation sequencing. We identified two subvariants, Marseille-4A, which contains 22 different lineages of at least 50 genomes, and Marseille-4B. Their average lifetime was 4.1±1.4 months, during which 4.1±2.6 mutations accumulated. Growth rate was 0.079±0.045, varying from 0.010 to 0.173. All the lineages exhibited a “gamma” distribution. Several beneficial mutations at unpredicted sites initiated a new outbreak, while the accumulation of other mutations resulted in more viral heterogenicity, increased diversity and vanishing of the lineages. Marseille-4B emerged when the other Marseille-4 lineages vanished. Its ORF8 gene was knocked out by a stop codon, as reported in several mink lineages and in the alpha variant. This subvariant was associated with increased hospitalization and death rates, suggesting that ORF8 is a nonvirulence gene. We speculate that the observed heterogenicity of a lineage may predict the end of the outbreak.

Analysis of SARS-CoV-2 variants from 24,181 patients exemplifies the role of globalisation and zoonosis in pandemics (preprint)

After the end of the first epidemic episode of SARS-CoV-2 infections, as cases began to rise again during the summer of 2020, we at IHU Mediterranee Infection in Marseille, France, intensified the genomic surveillance of SARS-CoV-2, and described the first viral variants. In this study, we compared the incidence curves of SARS-CoV-2-associated deaths in different countries and reported the classification of SARS-CoV-2 variants detected in our institute, as well as the kinetics and sources of the infections. We used mortality collected from a COVID-19 data repository for 221 countries. Viral variants were defined based on [≥]5 hallmark mutations shared by [≥]30 genomes. SARS-CoV-2 genotype was determined for 24,181 patients using next-generation genome and gene sequencing (in 47% and 11% of cases, respectively) or variant-specific qPCR (in 42% of cases). Sixteen variants were identified by analysing viral genomes from 9,788 SARS-CoV-2-diagnosed patients. Our data show that since the first SARS-CoV-2 epidemic episode in Marseille, importation through travel from abroad was documented for seven of the new variants. In addition, for the B.1.160 variant of Pangolin classification (a.k.a. Marseille-4), we suspect transmission from mink farms. In conclusion, we observed that the successive epidemic peaks of SARS-CoV-2 infections are not linked to rebounds of viral genotypes that are already present but to newly-introduced variants. We thus suggest that border control is the best mean of combating this type of introduction, and that intensive control of mink farms is also necessary to prevent the emergence of new variants generated in this animal reservoir.

Investigation of a COVID-19 Outbreak on an Aircraft Carrier: An Epidemic Model Based on Real Data (preprint)

Background: From mid-March to mid-April 2020, the French aircraft carrier Charles de Gaulle suffered a COVID-19 outbreak. An investigation was performed to describe the outbreak, including how the virus was introduced on board. We present the clinical pictures of COVID-19 cases with risk factors for infection and severity, effectiveness of preventive measures, and we discuss the real collective protective rate.Methods: A confirmed case was any service member with a positive SARS-CoV-2 RT-PCR and/or who presented symptoms of anosmia and/or ageusia. We considered the entire crew as a cohort and questioned them about individual, epidemiological, and clinical data. We performed viral genome sequencing and searched for SARS-CoV-2 in the environment.Results: The attack rate was 65% (1085/1767). The sex ratio was 6·9, and median age was 29 years. There were four clinical profiles: asymptomatic (13·0%), non-specific symptomatic (8·1%), specific symptomatic (76·3%), and severe (i.e. requiring oxygen therapy, 2·6%). Active smoking prevented severe COVID-19; age and obesity were risk factors.The instantaneous reproduction rate Rt and viral sequencing supported the hypothesis of several introductions of the virus on board, with an acceleration of the Rt when preventive measures were lifted. Physical distancing prevented infection (ORa, 0·55, 95% CI, 0·40-0·76). In the end, transmission stopped when the proportion of infected personnel was large enough to prevent the virus from circulating (65%, 95% CI, 62-68).Discussion: Asymptomatic and non-specific clinical pictures of COVID-19, combined with a lack of knowledge at that time about the specific symptoms of COVID-19 (anosmia, ageusia), delayed detection of the outbreak. Once it was identified, the lack of an isolation ward made it difficult to manage transmission on board, and the outbreak spread until a collective protective rate was reached. However, physical distancing was effective when applied. Syndromic surveillance and point-of-care biology could enable early detection of such viral emergences or outbreaks.Funding Information: No funding to declare.Declaration of Interests: The authors declare that they have no competing interests.Ethics Approval Statement: This was not an experimental protocol, but an outbreak investigation with routine care provided to infected individuals, so no ethical approval from any named institutional and/or licensing/ethics committee was required. We obtained individual informed consent to analyze data. No administrative authorization was required to access and use medical records. We chose not to provide certain details and to aggregate certain data in order to maintain patient anonymity. All methods were carried out in accordance with relevant guidelines and regulations.

Implementation of an in-house real-time reverse transcription-PCR assay for the rapid detection of the SARS-CoV-2 Marseille-4 variant (preprint)

IntroductionThe SARS-CoV-2 pandemic has been associated with the occurrence since summer 2020 of several viral variants that overlapped or succeeded each other in time. Those of current concern harbor mutations within the spike receptor binding domain (RBD) that may be associated with viral escape to immune responses. In our geographical area a viral variant we named Marseille-4 harbors a S477N substitution in this RBD. Materials and methodsWe aimed to implement an in-house one-step real-time reverse transcription-PCR (qPCR) assay with a hydrolysis probe that specifically detects the SARS-CoV-2 Marseille-4 variant. ResultsAll 6 cDNA samples from Marseille-4 variant strains identified in our institute by genome next-generation sequencing (NGS) tested positive using our Marseille-4 specific qPCR, whereas all 32 cDNA samples from other variants tested negative. In addition, 39/42 (93%) respiratory samples identified by NGS as containing a Marseille-4 variant strain and 0/26 samples identified as containing non-Marseille-4 variant strains were positive. Finally, 1,585/2,889 patients SARS-CoV-2-diagnosed in our institute, 10/277 (3.6%) respiratory samples collected in Algeria, and none of 207 respiratory samples collected in Senegal, Morocco, or Lebanon tested positive using our Marseille-4 specific qPCR. DiscussionOur in-house qPCR system was found reliable to detect specifically the Marseille-4 variant and allowed estimating it is involved in more than half of our SARS-CoV-2 diagnoses since December 2020. Such approach allows the real-time surveillance of SARS-CoV-2 variants, which is warranted to monitor and assess their epidemiological and clinical characterics based on comprehensive sets of data.

SARS-CoV-2 European resurgence foretold: interplay of introductions and persistence by leveraging genomic and mobility data (preprint)

Following the first wave of SARS-CoV-2 infections in spring 2020, Europe experienced a resurgence of the virus starting late summer that was deadlier and more difficult to contain. Relaxed intervention measures and summer travel have been implicated as drivers of the second wave. Here, we build a phylogeographic model to evaluate how newly introduced lineages, as opposed to the rekindling of persistent lineages, contributed to the COVID-19 resurgence in Europe. We inform this model using genomic, mobility and epidemiological data from 10 West European countries and estimate that in many countries more than 50% of the lineages circulating in late summer resulted from new introductions since June 15th. The success in onwards transmission of these lineages is predicted by SARS-CoV-2 incidence during this period. Relatively early introductions from Spain into the United Kingdom contributed to the successful spread of the 20A.EU1/B.1.177 variant. The pervasive spread of variants that have not been associated with an advantage in transmissibility highlights the threat of novel variants of concern that emerged more recently and have been disseminated by holiday travel. Our findings indicate that more effective and coordinated measures are required to contain spread through cross-border travel.

Introduction into the Marseille geographical area of a mild SARS-CoV-2 variant originating from sub-Saharan Africa (preprint)

BACKGROUNDIn Marseille, France, the COVID-19 incidence evolved unusually with several successive epidemic episodes. The second outbreak started in July, was associated with North Africa, and involved travelers and an outbreak on passenger ships. This suggested the involvement of a new viral variant. METHODSWe sequenced the genomes from 916 SARS-CoV-2 strains from COVID-19 patients in our institute. The patients demographic and clinical features were compared according to the infecting viral variant. RESULTSFrom June 26th to August 14th, we identified a new viral variant (Marseille-1). Based on genome sequences (n=89) or specific qPCR (n=53), 142 patients infected with this variant were detected. It is characterized by a combination of 10 mutations located in the nsp2, nsp3, nsp12, S, ORF3a, ORF8 and N/ORF14 genes. We identified Senegal and Gambia, where the virus had been transferred from China and Europe in February-April as the sources of the Marseille-1 variant, which then most likely reached Marseille through Maghreb when French borders reopened. In France, this variant apparently remained almost limited to Marseille. In addition, it was significantly associated with a milder disease compared to clade 20A ancestor strains. CONCLUSIONOur results demonstrate that SARS-CoV-2 can genetically diversify rapidly, its variants can diffuse internationally and cause successive outbreaks.

Genomic diversity and evolution of coronavirus (SARS-CoV-2) in France from 309 COVID-19-infected patients (preprint)

The novel coronavirus (SARS-CoV-2) causes pandemic of viral pneumonia. The evolution and mutational events of the SARS-CoV-2 genomes are critical for controlling virulence, transmissibility, infectivity, severity of symptoms and mortality associated to this infectious disease. We collected and investigated 309 SARS-CoV-2 genomes from patients infected in France. Detailed genome cartography of all mutational events (SNPs, indels) was reported and correlated to clinical features of patients. A comparative analysis between our 309 SARS-CoV-2 genomes from French patients and the reference Wuhan coronavirus genome revealed 315 substitution mutations and six deletion events: ten were in 5/3 UTR, 178 were nonsynonymous, 126 were synonymous and one generated a stop codon. Six different deleted areas were also identified in nine viral variants. In particular, 30 substitution mutations (18 nonsynonymous) and one deletion (21765-21770) concerned the spike S glycoprotein. An average of 7.8 mutational events (+/- 1.7 SD) and a median of 8 (range, 7-9) were reported per viral isolate. Comparative analyses and clustering of specific mutational signatures in 309 genomes disclose several divisions in groups and subgroups combining their geographical and phylogenetic origin. Clinical outcomes of the 309 COVID-19-infected patients were investigated according to the mutational signatures of viral variants. These findings highlight the genome dynamics of the coronavirus 2019-20 and shed light on the mutational landscape and evolution of this virus. Inclusion of the French cohort enabled us to identify 161 novel mutations never reported in SARS-CoV-2 genomes collected worldwide. These results support a global and continuing surveillance of the emerging variants of the coronavirus SARS-CoV-2.