A descriptive assessment of the National Institute of Public Health's contribution to the COVID-19 response in Cambodia, 2020-2021.

Objective: This paper examines the contributions made by the National Institute of Public Health to Cambodia's response to the coronavirus disease (COVID-19) pandemic during 2020-2021. Methods: The activities conducted by the Institute were compared with adaptations of the nine pillars of the World Health Organization's 2020 COVID-19 strategic preparedness and response plan. To gather relevant evidence, we reviewed national COVID-19 testing data, information about COVID-19-related events documented by Institute staff, and financial and technical reports of the Institute's activities. Results: The main contributions the Institute made were to the laboratory pillar and the incident management and planning pillar. The Institute tested more than 50% of the 2 575 391 samples for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing and provided technical advice about establishing 18 new laboratories for SARS-CoV-2 testing in the capital city of Phnom Penh and 11 provinces. The Institute had representatives on many national committees and coauthored national guidelines for implementing rapid COVID-19 testing, preventing transmission in health-care facilities and providing treatment. The Institute contributed to six other pillars, but had no active role in risk communication and community engagement. Discussion: The Institute's support was essential to the COVID-19 response in Cambodia, especially for laboratory services and incident management and planning. Based on the contributions made by the Institute during the COVID-19 pandemic, continued investment in it will be critical to allow it to support responses to future health emergencies in Cambodia.

Impact of oral intervention on the oral and overall health of children living with HIV in Cambodia: a randomized controlled trial.

BACKGROUND: Maintaining oral health is essential for improving overall health of children living with HIV. Therefore, we evaluated the effectiveness of an oral health intervention for improving their oral and overall health. In addition, we examined their longitudinal association between changes in oral and overall health. METHODS: We conducted a 2-year randomized controlled trial involving children living with HIV in Cambodia. Children aged 3-15 years and their caregivers were randomly allocated either to the intervention (group A) or control (group B) arm. A second control arm (group C) included children without HIV. The group A children received oral health education sessions and practiced home-based daily care. RESULTS: In the baseline survey, 482 children participated (group A: n = 160, group B: n = 168, group C: n = 154), and 350 completed the endline survey. An interaction effect in teeth brushing duration was observed in children in group A relative to group B (AOR = 2.69, 95% CI: 1.37-5.31) and group C (AOR = 3.78, 95% CI: 1.70-8.40). Longitudinal associations were observed between changes in oral hygiene and overall health, as presented by alterations in dental caries in permanent teeth with viral load detection (adjusted odds ratio = 3.58, 95% CI: 1.10 - 11.73), in salivary flow quantity with the overall quality of life (ß = 0.07, 95% CI: < 0.01 - 0.13), as well as in dental caries, salivary pH, debris index with body mass index for age among group A children. CONCLUSIONS: Oral health intervention may improve oral care behaviors and potentially enhance overall health among children living with HIV in antiretroviral therapy in a resource-constrained setting. TRIAL REGISTRATION: ISRCTN 15177479.

Descriptive assessment of COVID-19 responses and lessons learnt in Cambodia, January 2020 to June 2022.

As a member state of the International Health Regulations 2005, Cambodia is continuously strengthening its capacity to respond to health emergencies and prevent the international spread of diseases. Despite this, Cambodia's capacity to prevent, detect and rapidly respond to public health threats remained limited at the onset of the pandemic, as was the case in most countries. This paper describes epidemiological phases, response phases, strategy and lessons learnt in Cambodia between 27 January 2020 and 30 June 2022. We classified epidemiological phases in Cambodia into three phases, in which Cambodia responded using eight measures: (1) detect, isolate/quarantine; (2) face coverings, hand hygiene and physical distancing measures; (3) risk communication and community engagement; (4) school closures; (5) border closures; (6) public event and gathering cancellation; (7) vaccination; and (8) lockdown. The measures corresponded to six strategies: (1) setting up and managing a new response system, (2) containing the spread with early response, (3) strengthening the identification of cases and contacts, (4) strengthening care for patients with COVID-19, (5) boosting vaccination coverage and (6) supporting disadvantaged groups. Thirteen lessons were learnt for future health emergency responses. Findings suggest that Cambodia successfully contained the spread of SARS-CoV-2 in the first year and quickly attained high vaccine coverage by the second year of the response. The core of this success was the strong political will and high level of cooperation from the public. However, Cambodia needs to further improve its infrastructure for quarantining and isolating cases and close contacts and laboratory capacity for future health emergencies.

Sexual and reproductive health services access and provision in Cambodia during the COVID-19 pandemic: a mixed-method study of urban-rural differences.

BACKGROUND: The COVID-19 pandemic pushed governments worldwide to implement unprecedented mitigation measures, including safe-distancing, lockdowns, disruption of non-essential services, border closures and travel restrictions, with both potential to affect rural and urban service-users differently and unintended consequences including reductions in sexual and reproductive health (SRH) services. We aimed to explore rural-urban differences in progress and challenges in SRH services provision in Cambodia, particularly during initial months of the COVID-19 pandemic. METHODS: We used a mixed-methods study design, including a household survey of 423 adolescents and women aged 18-49 and semi-structured interviews with 21 healthcare providers. We analysed survey data using multivariable logistic regression to identify associations between rural-urban setting and contraceptive perceptions or access. We analysed interview data thematically. RESULTS: Rural-urban residence was significantly associated with reported perceptions about and access to contraceptives. Rural participants had higher odds of stating it was possible to change contraceptive methods early in the COVID-19 pandemic, compared with urban participants. Qualitative data showed that although SRH services continued, health-workers faced differential challenges in rural and urban areas, e.g. service-users not attending due to job losses in urban areas and not complying with safe-distancing and mask-wearing requests in rural areas. CONCLUSIONS: COVID-19 and inadequate mitigation responses differentially affected rural and urban SRH service providers and service-users, exacerbating existing socioeconomic stressors while adding new fears of infection, transport constraints, and reduced livelihoods. Added financial support could help mitigate challenges in both rural and urban areas.

Residual risk of mother-to-child transmission of HBV despite timely Hepatitis B vaccination: a major challenge to eliminate hepatitis B infection in Cambodia.

BACKGROUND: In countries with intermediate or high hepatitis B virus (HBV) endemicity, mother-to-child transmission (MTCT) represents the main route of chronic HBV infection. There is a paucity of information on HBV MTCT in Cambodia. This study aimed to investigate the prevalence of HBV infection among pregnant women and its MTCT rate in Siem Reap, Cambodia. METHODS: This longitudinal study included two parts, study-1 to screen HBsAg among pregnant women and study-2 to follow up babies of all HBsAg-positive and one-fourth of HBsAg-negative mothers at their delivery and six-month post-partum. Serum or dried blood spot (DBS) samples were collected to examine HBV sero-markers by chemiluminescent enzyme immunoassay (CLEIA), and molecular analyses were performed on HBsAg-positive samples. Structured questionnaires and medical records were used to examine the risk factors for HBV infection. MTCT rate was calculated by HBsAg positivity of 6-month-old babies born to HBsAg-positive mothers and ascertained by the homology of HBV genomes in mother-child pair at 6-month-old. RESULTS: A total of 1,565 pregnant women were screened, and HBsAg prevalence was 4.28% (67/1565). HBeAg positivity was 41.8% and was significantly associated with high viral load (p < 0.0001). Excluding subjects who dropped out due to restrictions during COVID-19, one out of 35 babies born to HBsAg-positive mothers tested positive for HBsAg at 6 months of age, despite receiving timely HepB birth dose and HBIG, followed by 3 doses of HepB vaccine. Hence the MTCT rate was 2.86%. The mother of the infected baby was positive for HBeAg and had a high HBV viral load (1.2 × 109 copies/mL). HBV genome analysis showed 100% homology between the mother and the child. CONCLUSIONS: Our findings illustrate the intermediate endemicity of HBV infection among pregnant women in Siem Reap, Cambodia. Despite full HepB vaccination, a residual risk of HBV MTCT was observed. This finding supports the recently updated guidelines for the prevention of HBV MTCT in 2021, which integrated screening and antiviral prophylaxis for pregnant women at risk of HBV MTCT. Furthermore, we strongly recommend the urgent implementation of these guidelines nationwide to effectively combat HBV in Cambodia.

Social contact patterns relevant for infectious disease transmission in Cambodia.

Social mixing patterns are key determinants of infectious disease transmission. Mathematical models parameterised with empirical data from contact pattern surveys have played an important role in understanding epidemic dynamics and informing control strategies, including for SARS-CoV-2. However, there is a paucity of data on social mixing patterns in many settings. We conducted a community-based survey in Cambodia in 2012 to characterise mixing patterns and generate setting-specific contact matrices according to age and urban/rural populations. Data were collected using a diary-based approach from 2016 participants, selected by stratified random sampling. Contact patterns were highly age-assortative, with clear intergenerational mixing between household members. Both home and school were high-intensity contact settings, with 27.7% of contacts occurring at home with non-household members. Social mixing patterns differed between rural and urban residents; rural participants tended to have more intergenerational mixing, and a higher number of contacts outside of home, work or school. Participants had low spatial mobility, with 88% of contacts occurring within 1 km of the participants' homes. These data broaden the evidence-base on social mixing patterns in low and middle-income countries and Southeast Asia, and highlight within-country heterogeneities which may be important to consider when modelling the dynamics of pathogens transmitted via close contact.

Influx of Backyard Farming with Limited Biosecurity Due to the COVID-19 Pandemic Carries an Increased Risk of Zoonotic Spillover in Cambodia.

Backyard farming with limited biosecurity creates a massive potential for zoonotic spillover. Cambodia, a developing nation in Southeast Asia, is a hub for emerging and endemic infectious diseases. Due to pandemic-induced job losses in the tourism sector, rumors suggest that many former Cambodian tour guides have turned to backyard farming as a source of income and food security. A cross-sectional study including 331 tour guides and 69 poultry farmers in Cambodia before and during the novel coronavirus disease 2019 (COVID-19) pandemic was conducted. Participants were administered a survey to assess food security, income, and general farming practices. Survey data were collected to evaluate the risk perceptions for avian influenza virus (AIV), antimicrobial resistance (AMR), and general biosecurity management implemented on these poultry farms. Overall, food security decreased for 80.1% of the tour guides during the COVID-19 pandemic. Approximately 21% of the tour guides interviewed used backyard poultry farming to supplement losses of income and food insecurity during the COVID-19 pandemic, with a significantly higher risk than for traditional poultry farmers. Agricultural intensification in Cambodia due to the COVID-19 pandemic has caused an influx of makeshift farms with limited biosecurity. Inadequate biosecurity measures in animal farms can facilitate spillover and contribute to future pandemics. Improved biosecurity and robust viral surveillance systems are critical for reducing the risk of spillover from backyard farms. IMPORTANCE While this study highlights COVID-19-associated changes in poultry production at a small scale in Cambodia, poultry production is expected to expand due to an increase in the global demand for poultry protein during the pandemic, changes in urbanization, and the reduction of the global pork supply caused by African swine fever (ASF). The global demand and surge in poultry products, combined with inadequate biosecurity methods, can lead to an increased risk of domestic animal and human spillovers of zoonotic pathogens such as avian influenza. Countries in regions of endemicity are often plagued by complex emergency situations (i.e., food insecurity and economic fallouts) that hinder efforts to effectively address the emergence (or reemergence) of zoonotic diseases. Thus, novel surveillance strategies for endemic and emerging infectious diseases require robust surveillance systems and biosecurity training programs to prevent future global pandemics.

Income loss and gender-based violence during the COVID-19 pandemic among female entertainment workers in Cambodia: a cross-sectional phone survey.

BACKGROUND: In Cambodia, female entertainment workers (FEWs) are disproportionately affected by global and local disasters, such as the COVID-19 pandemic. To prevent the spread of COVID-19, the government imposed tight restrictions, including closures of entertainment venues, such as karaoke bars, beer gardens, nightclubs, or massage parlors, leading FEWs to face economic and social disruptions. This study aims to assess the relationship between income loss during the pandemic and gender-based violence (GBV) among FEWs in Cambodia to inform future disaster response programs. METHODS: We conducted a phone survey in August 2021 with 369 randomly sampled FEWs from a national organization's email list. We used a structured questionnaire to ask the participants about job and income loss, food security, mental health, access to health services, and GBV. We fit a linear regression model to examine the differences in GBV experience between FEWs who lost all their income and those who lost partial income due to the COVID-19 pandemic. Key covariables comprised the number of dependents, smartphone ownership, internet access, food security, and mental health. Multivariable linear regression analysis was conducted. RESULTS: The mean age (31.6 vs. 30.6), years of formal education (6.3 vs. 6.3), marital status (24.2 vs. 23.8 never married), and the number of children (1.3 vs. 1.1) of women reporting having lost all income were not significantly different from those who experienced partial income loss. Overall, GBV experiences were significantly higher in FEWs who lost all income than in those who lost partial income (62.9% vs. 47.4%, p = 0.03). Controlling for the number of dependents, smartphone ownership, and food security, the adjusted odds ratio for GBV was significant in the adjusted model (AOR = 1.23 (1.08-1.40), p = 0.001) indicating that those who experienced total income loss were more likely to experience GBV than those who experienced partial income loss. In addition, they were significantly less likely to be food secure (p = 0.04), less likely to own a smartphone (p = 0.02), and had more dependents (p < 0.001). CONCLUSION: Disaster response programs should consider the implications of safety measures and government support for both formal and informal workers regarding safety, food access, and mental health support. Food assistance programs should target the most vulnerable informal sector workers during crises.

SARS-CoV-2 Cross-Reactivity in Prepandemic Serum from Rural Malaria-Infected Persons, Cambodia.

Inhabitants of the Greater Mekong Subregion in Cambodia are exposed to pathogens that might influence serologic cross-reactivity with severe acute respiratory syndrome coronavirus 2. A prepandemic serosurvey of 528 malaria-infected persons demonstrated higher-than-expected positivity of nonneutralizing IgG to spike and receptor-binding domain antigens. These findings could affect interpretation of large-scale serosurveys.

Presence of Recombinant Bat Coronavirus GCCDC1 in Cambodian Bats.

Bats have been recognized as an exceptional viral reservoir, especially for coronaviruses. At least three bat zoonotic coronaviruses (SARS-CoV, MERS-CoV and SARS-CoV-2) have been shown to cause severe diseases in humans and it is expected more will emerge. One of the major features of CoVs is that they are all highly prone to recombination. An extreme example is the insertion of the P10 gene from reoviruses in the bat CoV GCCDC1, first discovered in Rousettus leschenaultii bats in China. Here, we report the detection of GCCDC1 in four different bat species (Eonycteris spelaea, Cynopterus sphinx, Rhinolophus shameli and Rousettus sp.) in Cambodia. This finding demonstrates a much broader geographic and bat species range for this virus and indicates common cross-species transmission. Interestingly, one of the bat samples showed a co-infection with an Alpha CoV most closely related to RsYN14, a virus recently discovered in the same genus (Rhinolophus) of bat in Yunnan, China, 2020. Taken together, our latest findings highlight the need to conduct active surveillance in bats to assess the risk of emerging CoVs, especially in Southeast Asia.

Longitudinal monitoring in Cambodia suggests higher circulation of alpha and betacoronaviruses in juvenile and immature bats of three species.

Recent studies suggest that coronaviruses circulate widely in Southeast Asian bat species and that the progenitors of the SARS-Cov-2 virus could have originated in rhinolophid bats in the region. Our objective was to assess the diversity and circulation patterns of coronavirus in several bat species in Southeast Asia. We undertook monthly live-capture sessions and sampling in Cambodia over 17 months to cover all phases of the annual reproduction cycle of bats and test specifically the association between their age and CoV infection status. We additionally examined current information on the reproductive phenology of Rhinolophus and other bat species presently known to occur in mainland southeast China, Vietnam, Laos and Cambodia. Results from our longitudinal monitoring (573 bats belonging to 8 species) showed an overall proportion of positive PCR tests for CoV of 4.2% (24/573) in cave-dwelling bats from Kampot and 4.75% (22/463) in flying-foxes from Kandal. Phylogenetic analysis showed that the PCR amplicon sequences of CoVs (n = 46) obtained clustered in Alphacoronavirus and Betacoronavirus. Interestingly, Hipposideros larvatus sensu lato harbored viruses from both genera. Our results suggest an association between positive detections of coronaviruses and juvenile and immature bats in Cambodia (OR = 3.24 [1.46-7.76], p = 0.005). Since the limited data presently available from literature review indicates that reproduction is largely synchronized among rhinolophid and hipposiderid bats in our study region, particularly in its more seasonal portions (above 16° N), this may lead to seasonal patterns in CoV circulation. Overall, our study suggests that surveillance of CoV in insectivorous bat species in Southeast Asia, including SARS-CoV-related coronaviruses in rhinolophid bats, could be targeted from June to October for species exhibiting high proportions of juveniles and immatures during these months. It also highlights the need to develop long-term longitudinal surveys of bats and improve our understanding of their ecology in the region, for both biodiversity conservation and public health reasons.

A novel SARS-CoV-2 related coronavirus in bats from Cambodia.

Knowledge of the origin and reservoir of the coronavirus responsible for the ongoing COVID-19 pandemic is still fragmentary. To date, the closest relatives to SARS-CoV-2 have been detected in Rhinolophus bats sampled in the Yunnan province, China. Here we describe the identification of SARS-CoV-2 related coronaviruses in two Rhinolophus shameli bats sampled in Cambodia in 2010. Metagenomic sequencing identifies nearly identical viruses sharing 92.6% nucleotide identity with SARS-CoV-2. Most genomic regions are closely related to SARS-CoV-2, with the exception of a region of the spike, which is not compatible with human ACE2-mediated entry. The discovery of these viruses in a bat species not found in China indicates that SARS-CoV-2 related viruses have a much wider geographic distribution than previously reported, and suggests that Southeast Asia represents a key area to consider for future surveillance for coronaviruses.

Human Infection with Avian Influenza A(H9N2) Virus, Cambodia, February 2021.

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.

The Role of Micronutrients and Toxic Metals in the Management of Epidemics in Cambodia.

The illegal trade of wildlife in SE Asia has been identified as the likely cause of the COVID-19 pandemic. We reviewed 198 papers on the current COVID pandemic in Cambodia, diseases such as avian influenza and Nipah virus, most likely to develop into a new pandemic in Cambodia, and common features of disease that require mitigation. Artisanal goldmining uses pure mercury in the areas where wildlife is smuggled to China. Moreover, 30-40% of Cambodians are zinc deficient. High levels of arsenic in irrigation water (>1000 µg/L) are associated with very low levels of zinc in rice (5 µg/g) and rice is the primary staple food for the region. Brown rice from nine of 15 paddy fields in the arsenic zone of Cambodia had double the new guidelines of 100 µg/kg inorganic arsenic for children's food in the EU and USA. The combination of deficiencies of essential micronutrients like zinc and pervasive presence of arsenic and mercury has the potential to compromise the immunity of many Cambodians. Innovative solutions are suggested to improve micronutrient nutrition. Toxins that suppress the immune system must be better managed to reduce the virulence of pathogens. Cambodia was not likely the source of the COVID-19 but does have problems that could result in a new pandemic.

Genetic and Antigenic Characterization of an Influenza A(H3N2) Outbreak in Cambodia and the Greater Mekong Subregion during the COVID-19 Pandemic, 2020.

Introduction of non-pharmaceutical interventions to control COVID-19 in early 2020 coincided with a global decrease in active influenza circulation. However, between July and November 2020, an influenza A(H3N2) epidemic occurred in Cambodia and in other neighboring countries in the Greater Mekong Subregion in Southeast Asia. We characterized the genetic and antigenic evolution of A(H3N2) in Cambodia and found that the 2020 epidemic comprised genetically and antigenically similar viruses of Clade3C2a1b/131K/94N, but they were distinct from the WHO recommended influenza A(H3N2) vaccine virus components for 2020-2021 Northern Hemisphere season. Phylogenetic analysis revealed multiple virus migration events between Cambodia and bordering countries, with Laos PDR and Vietnam also reporting similar A(H3N2) epidemics immediately following the Cambodia outbreak: however, there was limited circulation of these viruses elsewhere globally. In February 2021, a virus from the Cambodian outbreak was recommended by WHO as the prototype virus for inclusion in the 2021-2022 Northern Hemisphere influenza vaccine. IMPORTANCE The 2019 coronavirus disease (COVID-19) pandemic has significantly altered the circulation patterns of respiratory diseases worldwide and disrupted continued surveillance in many countries. Introduction of control measures in early 2020 against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection has resulted in a remarkable reduction in the circulation of many respiratory diseases. Influenza activity has remained at historically low levels globally since March 2020, even when increased influenza testing was performed in some countries. Maintenance of the influenza surveillance system in Cambodia in 2020 allowed for the detection and response to an influenza A(H3N2) outbreak in late 2020, resulting in the inclusion of this virus in the 2021-2022 Northern Hemisphere influenza vaccine.

Costing analysis of field implementation of hepatitis C case detection in rural Maung Russey operational district, Cambodia.

BACKGROUND: When a new health programme is introduced, it is crucial to estimate the costs for rational health policy decision-making. The aim of this study was to determine the costs of implementing two strategies for hepatitis C virus (HCV) screening in rural Cambodia. METHODS: We retrospectively analysed clinical and cost data that were collected routinely for a demonstration project for scaling up HCV screening and testing in Cambodia. The programme data were collected between March and December 2018 in Maung Russey operational district in Battambang Province, Cambodia. FINDINGS: During the study period, 24 230 people were screened; 1194 (5%) were HCV seropositive, of whom 793 (66%) were confirmed to be viraemic. During the study period, 18% of the estimated population of the operational district were screened, of whom 45% were estimated to be seropositive and 41% to be viraemic. With passive screening alone, 8% of the estimated population were screened, of whom 29% were estimated to be seropositive and 28% viraemic. The cost per detected viraemic case was US$ 194 for passive screening alone and US$ 283 for passive and active screening combined. Labour costs (31%) and tests and materials (29%) comprised the largest proportions of the cost. CONCLUSION: Combined active and passive screening per viraemic case detected was US$ 89 more expensive than passive screening alone but provided a higher yield (41% versus 28%) of viraemic cases. Therefore, adding active screening to passive screening is beneficial. Selective active screening strategies, such as targeting people over 45 years and other higher-risk groups, added value for HCV diagnosis.

A novel comprehensive metric to assess effectiveness of COVID-19 testing: Inter-country comparison and association with geography, government, and policy response.

Testing and case identification are key strategies in controlling the COVID-19 pandemic. Contact tracing and isolation are only possible if cases have been identified. The effectiveness of testing should be assessed, but a single comprehensive metric is not available to assess testing effectiveness, and no timely estimates of case detection rate are available globally, making inter-country comparisons difficult. The purpose of this paper was to propose a single, comprehensive metric, called the COVID-19 Testing Index (CovTI) scaled from 0 to 100, derived from epidemiological indicators of testing, and to identify factors associated with this outcome. The index was based on case-fatality rate, test positivity rate, active cases, and an estimate of the detection rate. It used parsimonious modeling to estimate the true total number of COVID-19 cases based on deaths, testing, health system capacity, and government transparency. Publicly reported data from 165 countries and territories that had reported at least 100 confirmed cases by June 3, 2020 were included in the index. Estimates of detection rates aligned satisfactorily with previous estimates in literature (R2 = 0.44). As of June 3, 2020, the states with the highest CovTI included Hong Kong (93.7), Australia (93.5), Iceland (91.8), Cambodia (91.3), New Zealand (90.6), Vietnam (90.2), and Taiwan (89.9). Bivariate analyses showed the mean CovTI in countries with open public testing policies (66.9, 95% CI 61.0-72.8) was significantly higher than in countries with no testing policy (29.7, 95% CI 17.6-41.9) (p<0.0001). A multiple linear regression model assessed the association of independent grouping variables with CovTI. Open public testing and extensive contact tracing were shown to significantly increase CovTI, after adjusting for extrinsic factors, including geographic isolation and centralized forms of government. The correlation of testing and contact tracing policies with improved outcomes demonstrates the validity of this model to assess testing effectiveness and also suggests these policies were effective at improving health outcomes. This tool can be combined with other databases to identify other factors or may be useful as a standalone tool to help inform policymakers.

An influenza A (H3N2) virus outbreak in the Kingdom of Cambodia during the COVID-19 pandemic of 2020.

BACKGROUND: Global influenza virus circulation decreased during the COVID-19 pandemic, possibly due to widespread community mitigation measures. Cambodia eased some COVID-19 mitigation measures in June and July 2020. On 20 August a cluster of respiratory illnesses occurred among residents of a pagoda, including people who tested positive for influenza A but none who were positive for SARS-CoV-2. METHODS: A response team was deployed on 25 August 2020. People with influenza-like illness (ILI) were asked questions regarding demographics, illness, personal prevention measures, and residential arrangements. Respiratory swabs were tested for influenza and SARS-Cov-2 by real-time reverse transcription PCR, and viruses were sequenced. Sentinel surveillance data were analyzed to assess recent trends in influenza circulation in the community. RESULTS: Influenza A (H3N2) viruses were identified during sentinel surveillance in Cambodia in July 2020 prior to the reported pagoda outbreak. Among the 362 pagoda residents, 73 (20.2%) ILI cases were identified and 40 were tested, where 33/40 (82.5%) confirmed positive for influenza A (H3N2). All 40 were negative for SARS-CoV-2. Among the 73 residents with ILI, none were vaccinated against influenza, 47 (64%) clustered in 3/8 sleeping quarters, 20 (27%) reported often wearing a mask, 27 (36%) reported often washing hands, and 11 (15%) reported practicing social distancing. All viruses clustered within clade 3c2.A1 close to strains circulating in Australia in 2020. CONCLUSIONS: Circulation of influenza viruses began in the community following the relaxation of national COVID-19 mitigation measures, and prior to the outbreak in a pagoda with limited social distancing. Continued surveillance and influenza vaccination are required to limit the impact of influenza globally.