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Mpox is an infectious disease caused by the Monkeypox virus, which is divided into two main genetic clades: Clade I and Clade II. A large-scale outbreak linked to Clade IIb emerged in 2022 and rapidly spread to more than 100 countries worldwide. Here, we describe the first and only documented Mpox outbreak in Cambodia (2023-2024), the public health outbreak response efforts and analysis, and integrating epidemiological and genomic approaches.To investigate the outbreak, samples from suspect cases were confirmed using qPCR before virus whole genome sequences were obtained for phylogenomic analyses.Epidemiological investigation revealed transmission primarily through intimate contact within socially connected networks, exclusively among men who have sex with men. None of the confirmed cases reported recent international travel or zoonotic exposure. Phylogenomic analysis showed that all Cambodian Mpox genomes belonged to lineage C.1, nested within Clade IIb. Bayesian analysis of publicly available C.1 genomes indicated that the most closely related sequence was from Thailand. Monophyletic clustering of Cambodian sequences, alongside a high proportion of APOBEC3 mutations, indicates localized human-to-human transmission after introduction.Altogether, these results illustrate the risk of regional lineages like C.1 introducing Mpox into previously unaffected countries, where socially connected human networks can sustain outbreaks despite control efforts.

Background Tracking the emergence, introduction and spread of SARS-CoV-2 variants of concern are essential for informing public health strategies. In 2021, Cambodia faced two major epidemic waves of SARS-CoV-2 triggered by the successive rise of the Alpha and Delta variants. Methods Phylodynamic analysis of 1,163 complete SARS-CoV-2 genomes from Cambodia, along with global sequences, were conducted between February and September 2021 to infer viral introductions, molecular epidemiology and population dynamics. The relationship between epidemic trends and control strategies were evaluated. Bayesian phylogeographic reconstruction was employed to estimate and contrast the spatiotemporal dynamics of the Alpha and Delta variants over time. Results Here we reveal that the Alpha variant displays rapid lineage diversification, accompanied by the acquisition of a spike E484K mutation that coincides with the national implementation of mass COVID-19 vaccination. Despite nationwide control strategies and increased vaccination coverage, the Alpha variant was quickly displaced by Delta variants that exhibits a higher effective reproductive number. Phylogeographic inference indicates that the Alpha variant was introduced through south-central region of Cambodia, with strong diffusion rates from the capital of Phnom Penh to other provinces, while the Delta variant likely entered the country via the northern border provinces. Conclusions Continual genomic surveillance and sequencing efforts, in combination with public health strategies, play a vital role in effectively tracking and responding to the emergence, evolution and dissemination of future emerging variants. Plain language summary Tracking how SARS-CoV-2, the virus that causes COVID-19, changes over time is important for public health. In Cambodia, there were two major COVID-19 waves in 2021, driven by the Alpha and Delta variants. We analyzed 1,163 virus samples from Cambodia, plus samples from other places, to understand how these variants spread. We found that the Alpha variant quickly spread and changed as Cambodia started a mass vaccination campaign. Despite efforts to control it, the Delta variant, which spreads more easily, soon took over. The Alpha variant likely came into Cambodia from the south, while the Delta variant probably entered from the north. Monitoring these changes helps us respond better to future outbreaks. Su et al. dissect SARS-CoV-2 variant patterns in Cambodia. They uncover divergent evolutionary trajectories and population dynamics, along with contrasting migration patterns, between Alpha and Delta variants in 2021.

Avian Influenza A(H5N1) Virus in Cambodia In this report from Cambodia, 16 human cases of highly pathogenic avian influenza A(H5N1) virus infection that occurred from February 2023 through August 2024 are described.

Abstract The first case of coronavirus disease 2019 (COVID-19) in Cambodia was confirmed on 27 January 2020 in a traveller from Wuhan. Cambodia subsequently implemented strict travel restrictions, and although intermittent cases were reported during the first year of the COVID-19 pandemic, no apparent widespread community transmission was detected. Investigating the routes of severe acute respiratory coronavirus 2 (SARS-CoV-2) introduction into the country was critical for evaluating the implementation of public health interventions and assessing the effectiveness of social control measures. Genomic sequencing technologies have enabled rapid detection and monitoring of emerging variants of SARS-CoV-2. Here, we detected 478 confirmed COVID-19 cases in Cambodia between 27 January 2020 and 14 February 2021, 81.3 per cent in imported cases. Among them, fifty-four SARS-CoV-2 genomes were sequenced and analysed along with representative global lineages. Despite the low number of confirmed cases, we found a high diversity of Cambodian viruses that belonged to at least seventeen distinct PANGO lineages. Phylogenetic inference of SARS-CoV-2 revealed that the genetic diversity of Cambodian viruses resulted from multiple independent introductions from diverse regions, predominantly, Eastern Asia, Europe, and Southeast Asia. Most cases were quickly isolated, limiting community spread, although there was an A.23.1 variant cluster in Phnom Penh in November 2020 that resulted in a small-scale local transmission. The overall low incidence of COVID-19 infections suggests that Cambodia’s early containment strategies, including travel restrictions, aggressive testing and strict quarantine measures, were effective in preventing large community outbreaks of COVID-19.

Bats and their ectoparasites are significant reservoirs and potential vectors of emerging zoonotic pathogens, yet the viral diversity within bat-associated arthropods remains poorly characterized. This study reports the identification of a novel coltivirus (order Reovirales), provisionally designated Stricticimex coltivirus (SCCV), in a newly described bat bug species, Stricticimex phnomsampovensis, collected from cave-dwelling wrinkle-lipped free-tailed bats (Mops plicatus) in Cambodia. Metagenomic sequencing and phylogenetic analysis revealed that SCCV clusters within the Coltivirus genus, showing closest similarity to Tai Forest Reovirus (TFRV) previously isolated from African bats. SCCV was detected in 18.4% of examined bat bugs and successfully isolated in VeroE6 cells, with replication confirmed in multiple mammalian cell lines. The discovery of SCCV extends the known diversity and geographic range of Coltivirus and highlights bat ectoparasites as overlooked hosts of potentially zoonotic viruses. These findings underscore the importance of integrated One Health surveillance targeting both bats and their ectoparasites to better assess the risk of pathogen spillover in biodiverse regions with high human-animal contact.

Circulating bat coronaviruses present a significant pandemic threat, yet our understanding of their genetic diversity and evolutionary dynamics remains limited. Over 3 years, we sampled 1,462 bats in Cambodia Steung Treng province, identifying extensive and diverse coronaviruses co-circulation. Using metatranscriptomic and amplicon sequencing, we generated 33 complete sarbecovirus genomes, revealing novel lineages that cluster into four distinct groups, each associated with different Rhinolophus bat species. Our analysis highlights rapid migration and recombination of sarbecovirus lineages over short distances and timescales. Of note, the receptor-binding domains of two novel viral groups exhibit high similarity to SARS-CoV-2, and pseudovirus assays confirmed the ability of this spike protein to mediate entry into cells expressing human ACE2, suggesting a potential zoonotic risk. The observed genetic diversity underscores the urgent need for continuous surveillance to identify high-risk animal-to-human interfaces and inform pandemic preparedness.