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In February 2021, routine sentinel surveillance for influenza-like illness in Cambodia detected a human avian influenza A(H9N2) virus infection. Investigations identified no recent H9N2 virus infections in 43 close contacts. One chicken sample from the infected child’s house was positive for H9N2 virus and genetically similar to the human virus.

There are approximately 35,000 human deaths from rabies in Asia annually. Rabies can be prevented through timely post-exposure prophylaxis (PEP) consisting of wound washing, rabies vaccine, and in some cases, rabies immunoglobulin (RIG). However, access to rabies PEP often remains limited to urban areas and is cost-prohibitive. There is little information on procurement, distribution, monitoring, and reporting of rabies PEP. We interviewed key informants in the public sector from various levels in Bangladesh, Bhutan, Cambodia, and Sri Lanka between March 2017 and May 2018 using a descriptive assessment tool to obtain information on procurement, distribution, monitoring, and reporting of rabies PEP. These four countries in Asia were chosen to showcase a range of rabies PEP systems. National rabies focal points were interviewed in each country and focal points helped identify additional key informants at lower levels. A total of 22 key informants were interviewed at various levels (central level to health facility level) including national rabies focal points in each country. Each country has a unique system for managing rabies PEP procurement, distribution, monitoring, and reporting. There are varying levels of PEP access for those with potential rabies exposures. Rabies PEP is available in select health facilities throughout the country in Bangladesh, Bhutan, and Sri Lanka. In Cambodia, rabies PEP is limited to two urban centers. The availability of RIG in all four countries is limited. In these four countries, most aspects of the rabies PEP distribution system operate independently of systems for other vaccines. However, in Bhutan, rabies PEP and Expanded Programme on Immunization (EPI) vaccines share cold chain space in some locations at the lowest level. All countries have a monitoring system in place, but there is limited reporting of data, particularly to the central level. Systems to procure, deliver, monitor, and report on rabies PEP are variable across countries. Sharing information on practices more widely among countries can help programs to increase access to this life-saving treatment.

In September 2017, a severe trichinellosis outbreak occurred in Cambodia after persons consumed raw wild pig meat; 33 persons were infected and 8 died. We collected and analyzed the medical records for 25 patients. Clinical signs and symptoms included myalgia, facial or peripheral edema, asthenia, and fever. We observed increased levels of creatine phosphokinase and aspartate aminotransferase-, as well as eosinophilia. Histopathologic examination of muscle biopsy specimens showed nonencapsulated Trichinella larvae. A Trichinella excretory/secretory antigen ELISA identified Trichinella IgM and IgG. Biopsy samples were digested and larvae were isolated and counted. PCR for the 5S rDNA intergenic spacer region and a multiplex PCR, followed by sequencing identified the parasite as Trichinella papuae. This species was identified in Papua New Guinea during 1999 and in several outbreaks in humans in Thailand. Thus, we identified T. papuae nematodes in humans in Cambodia.

Although the current pandemic of cholera originated in Asia, reports of cholera cases and outbreaks in the region are sparse. To provide a sub-regional assessment of cholera in South and Southeast Asia, we collated published and unpublished data from existing surveillance systems from Bangladesh, Cambodia, India, Malaysia, Nepal, Pakistan, Philippines, Thailand and Vietnam. Data from existing country surveillance systems on diarrhea, acute watery diarrhea, suspected cholera and/or confirmed cholera in nine selected Asian countries (Bangladesh, Cambodia, India, Malaysia, Nepal, Pakistan, Philippines, Thailand and Vietnam) from 2011 to 2015 (or 2016, when available) were collated. We reviewed annual cholera reports from WHO and searched PubMed and/or ProMED to complement data, where information is not completely available. From 2011 to 2016, confirmed cholera cases were identified in at least one year of the 5- or 6-year period in the countries included. Surveillance for cholera exists in most countries, but cases are not always reported. India reported the most number of confirmed cases with a mean of 5964 cases annually. The mean number of cases per year in the Philippines, Pakistan, Bangladesh, Malaysia, Nepal and Thailand were 760, 592, 285, 264, 148 and 88, respectively. Cambodia and Vietnam reported 51 and 3 confirmed cholera cases in 2011, with no subsequent reported cases. We present consolidated results of available surveillance in nine Asian countries and supplemented these with publication searches. There is paucity of readily accessible data on cholera in these countries. We highlight the continuing existence of the disease even in areas with improved sanitation and access to safe drinking water. Continued vigilance and improved surveillance in countries should be strongly encouraged.

The duration of humoral and cellular immune memory following SARS-CoV-2 infection in populations in least developed countries remains understudied but is key to overcome the current SARS-CoV-2 pandemic. Sixty-four Cambodian individuals with laboratory-confirmed infection with asymptomatic or mild/moderate clinical presentation were evaluated for Spike (S)-binding and neutralizing antibodies and antibody effector functions during acute phase of infection and at 6-9 months follow-up. Antigen-specific B cells, CD4 + and CD8 + T cells were characterized, and T cells were interrogated for functionality at late convalescence. Anti-S antibody titers decreased over time, but effector functions mediated by S-specific antibodies remained stable. S- and nucleocapsid (N)-specific B cells could be detected in late convalescence in the activated memory B cell compartment and are mostly IgG + . CD4 + and CD8 + T cell immune memory was maintained to S and membrane (M) protein. Asymptomatic infection resulted in decreased antibody-dependent cellular cytotoxicity (ADCC) and frequency of SARS-CoV-2-specific CD4 + T cells at late convalescence. Whereas anti-S antibodies correlated with S-specific B cells, there was no correlation between T cell response and humoral immune memory. Hence, all aspects of a protective immune response are maintained up to nine months after SARS-CoV-2 infection and in the absence of re-infection.

The East/Central/South African genotype of Chikungunya virus with the E1-A226V mutation emerged in 2011 in Cambodia and spread in 2012. An outbreak of 190 cases was documented in Trapeang Roka, a rural village. We surveyed 425 village residents within 3-4 weeks after the outbreak, and determined the sensitivity and specificity of case definitions and factors associated with infection by CHIKV. Self-reported clinical presentation consisted mostly of fever, rash and arthralgia. The presence of all three clinical signs or symptoms was identified as the most sensitive (67%) and specific (84%) self-reported diagnostic clinical indicator compared to biological confirmation by MAC-ELISA or RT-PCR used as a reference. Having an indoor occupation was associated with lower odds of infection compared with people who remained at home (adjOR 0.32, 95%CI 0.12-0.82). In contrast with findings from outbreaks in other settings, persons aged above 40 years were less at risk of CHIKV infection, likely reflecting immune protection acquired when Chikungunya circulated in Cambodia before the Khmer Rouge regime in 1975. In view of the very particular history of Cambodia, our epidemiological data from Trapeang Roka are the first to support the persistence of CHIKV antibodies over a period of 40 years.

Cross-border disease transmission is a key challenge for prevention and control of outbreaks. Variation in surveillance structure and national guidelines used in different countries can affect their data quality and the timeliness of outbreak reports. This study aimed to evaluate timeliness and data quality of national outbreak reporting for four countries in the Mekong Basin Disease Surveillance network (MBDS). Data on disease outbreaks occurring from 2010 to 2015 were obtained from the national disease surveillance reports of Cambodia, Lao PDR, Myanmar, and Vietnam. Data included total cases, geographical information, and dates at different timeline milestones in the outbreak detection process. Nine diseases or syndromes with public health importance were selected for the analysis including: dengue, food poisoning & diarrhea, severe diarrhea, diphtheria, measles, H5N1 influenza, H1N1 influenza, rabies, and pertussis. Overall, 2,087 outbreaks were reported from the four countries. The number of outbreaks and number of cases per outbreak varied across countries and diseases, depending in part on the outbreak definition used in each country. Dates on index onset, report, and response were >95% complete in all countries, while laboratory confirmation dates were 10%-100% incomplete in most countries. Inconsistent and out of range date data were observed in 1%-5% of records. The overall timeliness of outbreak report, response, and public communication was within 1-15 days, depending on countries and diseases. Diarrhea and severe diarrhea outbreaks showed the most rapid time to report and response, whereas diseases such as rabies, pertussis and diphtheria required a longer time to report and respond. The hierarchical structure of the reporting system, data collection method, and country's resources could affect the data quality and timeliness of the national outbreak reporting system. Differences in data quality and timeliness of outbreak reporting system among member countries should be considered when planning data sharing strategies within a regional network.

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.

Diarrheal infection remains a major public health problem in low and middle-income countries (LMICs). Prevention and control of diarrheal diseases are considered a global health priority. This case-control study aims to describe the prevalence of diarrhea etiologic agents and antimicrobial resistance in bacterial enteropathogens for acute diarrhea among children, adult civilians, and military personnel in Cambodia, detecting over 20 bacterial species, viruses, and parasites. A total of 918 subjects with acute diarrhea (cases), 791 aged-matched subjects without diarrhea (controls), and 675 follow-up cases were enrolled from five hospitals in Battambang and Oddor Meanchey provinces from 2020 to 2023. Pathogens were identified from collected stool samples via bacteriology, molecular techniques, immunoassays, and microscopy. Bacterial isolates were tested for antibiotic resistance patterns. From enrolled diarrhea cases, 533 stool samples (58%) were positive for enteric pathogens, compared to 389 samples (49%) in controls, underscoring the high carriage rate of enteric pathogens in this population as well as the difficulties in establishing the etiology of diarrhea cases. The most common enteric pathogens in cases were enteric bacteria with Aeromonas (15%), followed by Plesiomonas (12%), and enteroaggregative E. coli (EAEC) (10%). Shigella ( p  < 0.05), enterotoxigenic E. coli with heat-stable toxins (ETEC-ST) ( p  < 0.01), and Plesiomonas ( p  < 0.01) had a statistically significant association with acute diarrhea cases. Rotavirus was the most common virus found (51% of cases with virus), followed by norovirus (19%), and sapovirus (16%). In terms of antimicrobial resistance, 84% of Shigella isolates were highly resistant to trimethoprim/sulfamethoxazole (SXT), almost 80% of Campylobacter jejuni isolates were resistant to ciprofloxacin (82%) and nalidixic acid (85%). Over 50% of ETEC, Shigella , and EAEC isolates were resistant to ceftriaxone, ciprofloxacin, and SXT, respectively. Overall, our study highlights the high endemicity of enteric bacterial pathogens and the significant carriage rates of these pathogens even in individuals without overt symptoms. Although the overall antimicrobial resistance was moderate, prevalent isolates harbor a significant resistance to the first-line of treatment. This highlights the importance of ongoing diarrhea etiology and antimicrobial resistance (AMR) surveillance efforts to guide the development and implementation of an effective AMR management program in diarrheal infections.

Leptospirosis is an emerging but neglected public health challenge in the Asia/Pacific Region with an annual incidence estimated at 10-100 per 100,000 population. No accurate data, however, are available for at-risk rural Cambodian communities. We conducted anonymous, unlinked testing for IgM antibodies to Leptospira spp. on paired sera of Cambodian patients <20 years of age between 2007-2009 collected through active, community-based surveillance for febrile illnesses in a convenience sample of 27 rural and semi-rural villages in four districts of Kampong Cham province, Cambodia. Leptospirosis testing was done on paired serological samples negative for Dengue, Japanese encephalitis and Chikungunya viruses after random selection. Convalescent samples found positive while initial samples were negative were considered as proof of acute infection. We then applied a mathematical model to estimate the risk of fever caused by leptospirosis, dengue or other causes in rural Cambodia. A total of 630 samples are coming from a randomly selected subset of 2358 samples. IgM positive were found on the convalescent serum sample, among which 100 (15.8%) samples were IgM negative on an earlier sample. Seventeen of these 100 seroconversions were confirmed using a Microagglutination Test. We estimated the probability of having a fever due to leptospirosis at 1. 03% (95% Credible Interval CI: 0. 95%-1. 22%) per semester. In comparison, this probability was 2. 61% (95% CI: 2. 55%, 2. 83%) for dengue and 17. 65% (95% CI: 17. 49%, 18. 08%) for other causes. Our data from febrile cases aged below 20 years suggest that the burden of leptospirosis is high in rural Cambodian communities. This is especially true during the rainy season, even in the absence of identified epidemics.