Human-to-human transmission of Chlamydia psittaci in China, 2020: an epidemiological and aetiological investigation.

BACKGROUND: Chlamydia psittaci can infect a wide range of avian species, occasionally causing psittacosis (also known as parrot fever) in humans. Most human psittacosis cases are associated with close contact with pet birds or poultry. In December, 2020, an outbreak of severe community-acquired pneumonia of unknown aetiology was reported in a hospital in Shandong province, China, and some of the patients' close contacts had respiratory symptoms. Our aims were to determine the causative agent of this epidemic and whether there had been human-to-human transmission. METHODS: For this epidemiological and aetiological investigation study, we enrolled patients who had community-acquired pneumonia confirmed by chest CT at two local hospitals in Shandong Province in China. We collected sputum, bronchoalveolar lavage fluid, and nasopharyngeal swab samples from participants and detected pathogens by surveying for 22 target respiratory microbes using a commercial assay, followed by metagenomic next-generation sequencing, specific nested PCR, and qPCR tests. We excluded individuals who were C psittaci-negative on both tests. We recruited close contacts of the C psittaci-positive patients, and tested nasopharyngeal swabs from the close contacts and samples from ducks from the processing plant where these patients worked. We then integrated the epidemiological, clinical, and laboratory data to reveal the potential chain of transmission of C psittaci that characterised this outbreak. FINDINGS: Between Dec 4 and 29, 2020, we used metagenomic next-generation sequencing and different PCR-based approaches to test 12 inpatients with community-acquired pneumonia, of whom six (50%) were workers at a duck-meat processing plant and two (17%) were unemployed people, who were positive for C psittaci and enrolled in this study. We contacted 61 close contacts of the six patients who worked at the duck-meat processing plant, of whom 61 (100%) were enrolled and tested, and we determined that the community-acquired pneumonia outbreak was caused by C psittaci. Within the outbreak cluster, 17 (77%) of 22 participants had confirmed C psittaci infections and five (23%) of 22 participants were asymptomatic C psittaci carriers. The outbreak had begun with avian-to-human transmission, and was followed by secondary and tertiary human-to-human transmission, which included transmission by several asymptomatic carriers and by health-care workers. In addition, some of the participants with confirmed C psittaci infection had no identified source of infection, which suggested cryptic bacterial transmission. INTERPRETATION: Our study data might represent the first documented report of human-to-human transmission of C psittaci in China. Therefore, C psittaci has the potential to evolve human-to-human transmission via various routes, should be considered an elevated biosecurity and emergent risk, and be included as part of the routine diagnosis globally, especially for high-risk populations. FUNDING: Academic Promotion Programme of Shandong First Medical University, National Science and Technology Major Project, ARC Australian Laureate Fellowship.

Identification of a recombinant equine coronavirus in donkey, China.

Equine coronavirus (ECoV) was first identified in the USA and has been previously described in several countries. In order to test the presence of ECoV in China, we collected 51 small intestinal samples from donkey foals with diarrhoea from a donkey farm in Shandong Province, China between August 2020 and April 2021. Two samples tested positive for ECoV and full-length genome sequences were successfully obtained using next-generation sequencing, one of which was further confirmed by Sanger sequencing. The two strains shared 100% sequence identity at the scale of whole genome. Bioinformatics analyses further showed that the two Chinese strains represent a novel genetic variant of ECoV and shared the highest sequence identity of 97.05% with the first identified ECoV strain - NC99. In addition, it may be a recombinant, with the recombination region around the NS2 gene. To our knowledge, this is the first documented report of ECoV in China, highlighting its risk to horse/donkey breeding. In addition, its potential risk to public health also warrants further investigation.

Identification of novel bat coronaviruses sheds light on the evolutionary origins of SARS-CoV-2 and related viruses.

Despite the discovery of animal coronaviruses related to SARS-CoV-2, the evolutionary origins of this virus are elusive. We describe a meta-transcriptomic study of 411 bat samples collected from a small geographical region in Yunnan province, China, between May 2019 and November 2020. We identified 24 full-length coronavirus genomes, including four novel SARS-CoV-2-related and three SARS-CoV-related viruses. Rhinolophus pusillus virus RpYN06 was the closest relative of SARS-CoV-2 in most of the genome, although it possessed a more divergent spike gene. The other three SARS-CoV-2-related coronaviruses carried a genetically distinct spike gene that could weakly bind to the hACE2 receptor in vitro. Ecological modeling predicted the co-existence of up to 23 Rhinolophus bat species, with the largest contiguous hotspots extending from South Laos and Vietnam to southern China. Our study highlights the remarkable diversity of bat coronaviruses at the local scale, including close relatives of both SARS-CoV-2 and SARS-CoV.

Population Bottlenecks and Intra-host Evolution During Human-to-Human Transmission of SARS-CoV-2.

The emergence of the novel human coronavirus, SARS-CoV-2, causes a global COVID-19 (coronavirus disease 2019) pandemic. Here, we have characterized and compared viral populations of SARS-CoV-2 among COVID-19 patients within and across households. Our work showed an active viral replication activity in the human respiratory tract and the co-existence of genetically distinct viruses within the same host. The inter-host comparison among viral populations further revealed a narrow transmission bottleneck between patients from the same households, suggesting a dominated role of stochastic dynamics in both inter-host and intra-host evolutions.

Intra-host variation and evolutionary dynamics of SARS-CoV-2 populations in COVID-19 patients.

BACKGROUND: Since early February 2021, the causative agent of COVID-19, SARS-CoV-2, has infected over 104 million people with more than 2 million deaths according to official reports. The key to understanding the biology and virus-host interactions of SARS-CoV-2 requires the knowledge of mutation and evolution of this virus at both inter- and intra-host levels. However, despite quite a few polymorphic sites identified among SARS-CoV-2 populations, intra-host variant spectra and their evolutionary dynamics remain mostly unknown. METHODS: Using high-throughput sequencing of metatranscriptomic and hybrid captured libraries, we characterized consensus genomes and intra-host single nucleotide variations (iSNVs) of serial samples collected from eight patients with COVID-19. The distribution of iSNVs along the SARS-CoV-2 genome was analyzed and co-occurring iSNVs among COVID-19 patients were identified. We also compared the evolutionary dynamics of SARS-CoV-2 population in the respiratory tract (RT) and gastrointestinal tract (GIT). RESULTS: The 32 consensus genomes revealed the co-existence of different genotypes within the same patient. We further identified 40 intra-host single nucleotide variants (iSNVs). Most (30/40) iSNVs presented in a single patient, while ten iSNVs were found in at least two patients or identical to consensus variants. Comparing allele frequencies of the iSNVs revealed a clear genetic differentiation between intra-host populations from the respiratory tract (RT) and gastrointestinal tract (GIT), mostly driven by bottleneck events during intra-host migrations. Compared to RT populations, the GIT populations showed a better maintenance and rapid development of viral genetic diversity following the suspected intra-host bottlenecks. CONCLUSIONS: Our findings here illustrate the intra-host bottlenecks and evolutionary dynamics of SARS-CoV-2 in different anatomic sites and may provide new insights to understand the virus-host interactions of coronaviruses and other RNA viruses.

Multiple approaches for massively parallel sequencing of SARS-CoV-2 genomes directly from clinical samples.

BACKGROUND: COVID-19 (coronavirus disease 2019) has caused a major epidemic worldwide; however, much is yet to be known about the epidemiology and evolution of the virus partly due to the scarcity of full-length SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) genomes reported. One reason is that the challenges underneath sequencing SARS-CoV-2 directly from clinical samples have not been completely tackled, i.e., sequencing samples with low viral load often results in insufficient viral reads for analyses. METHODS: We applied a novel multiplex PCR amplicon (amplicon)-based and hybrid capture (capture)-based sequencing, as well as ultra-high-throughput metatranscriptomic (meta) sequencing in retrieving complete genomes, inter-individual and intra-individual variations of SARS-CoV-2 from serials dilutions of a cultured isolate, and eight clinical samples covering a range of sample types and viral loads. We also examined and compared the sensitivity, accuracy, and other characteristics of these approaches in a comprehensive manner. RESULTS: We demonstrated that both amplicon and capture methods efficiently enriched SARS-CoV-2 content from clinical samples, while the enrichment efficiency of amplicon outran that of capture in more challenging samples. We found that capture was not as accurate as meta and amplicon in identifying between-sample variations, whereas amplicon method was not as accurate as the other two in investigating within-sample variations, suggesting amplicon sequencing was not suitable for studying virus-host interactions and viral transmission that heavily rely on intra-host dynamics. We illustrated that meta uncovered rich genetic information in the clinical samples besides SARS-CoV-2, providing references for clinical diagnostics and therapeutics. Taken all factors above and cost-effectiveness into consideration, we proposed guidance for how to choose sequencing strategy for SARS-CoV-2 under different situations. CONCLUSIONS: This is, to the best of our knowledge, the first work systematically investigating inter- and intra-individual variations of SARS-CoV-2 using amplicon- and capture-based whole-genome sequencing, as well as the first comparative study among multiple approaches. Our work offers practical solutions for genome sequencing and analyses of SARS-CoV-2 and other emerging viruses.