Human respiratory syncytial virus (HRSV) is the leading cause of hospitalization of children aged <5 years due to respiratory illness in industrialized countries, and pneumonia is the leading cause of mortality among children aged <5 years worldwide. Although HRSV was first identified in 1956, a preventative vaccine has yet to be developed. Here we report the results of the first study to investigate the circulation and genetic diversity of HRSV in Cambodia among an all-ages population over 5 consecutive years. The incidences of HRSV infection among all-ages outpatient and hospitalized populations were equivalent, at 9.5% and 8.2%, respectively. Infection was most prevalent among children aged <5 years, with bronchiolitis being the most frequently observed clinical syndrome in the same age group. Circulation of HRSV was seasonal, typically coinciding with the rainy season between July and November annually. Strains belonging to HRSV groups A and B were detected with equivalent frequencies; however, we observed a potentially biennial shift in the predominant circulating HRSV genotype. The majority of HRSV group B strains belonged to the recently described BA genotype, with the exception of 10 strains classified as belonging to a novel HRSV group B genotype, SAB4, first reported here.

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To determine potential risk for bird-to-human transmission during infl uenza A virus (H5N1) outbreaks among backyard poultry in rural Cambodia, we collected environmental specimens. Viral RNA was detected in 27 (35%) of 77 specimens of mud, pond water, water plants, and soil swabs. Our results underscore the need for regular disinfection of poultry areas.

Transmission is low despite extensive human contact with poultry.

Acute respiratory infections are a major cause of mortality and morbidity worldwide. Using multiplex PCR/RT-PCR methods for the detection of 18 respiratory viruses, the circulation of those viruses during 3 consecutive dry seasons in Cambodia was described. Among 234 patients who presented with influenza-like illness, 35.5% were positive for at least one virus. Rhinoviruses (43.4%), parainfluenza (31.3%) viruses and coronaviruses (21.7%) were the most frequently detected viruses. Influenza A virus, parainfluenza virus 4 and SARS-coronavirus were not detected during the study period. Ninety apparently healthy individuals were included as controls and 10% of these samples tested positive for one or more respiratory viruses. No significant differences were observed in frequency and in virus copy numbers for rhinovirus detection between symptomatic and asymptomatic groups. This study raises questions about the significance of the detection of some respiratory viruses, especially using highly sensitive methods, given their presence in apparently healthy individuals. The link between the presence of the virus and the origin of the illness is therefore unclear.

BackgroundThere is little information about influenza disease among the Cambodian population. To better understand the dynamics of influenza in Cambodia, the Cambodian National Influenza Center (NIC) was established in August 2006. To continuously monitor influenza activity, a hospital based sentinel surveillance system for ILI (influenza like illness) with a weekly reporting and sampling scheme was established in five sites in 2006. In addition, hospital based surveillance of acute lower respiratory infection (ALRI) cases was established in 2 sites.MethodsThe sentinel sites collect weekly epidemiological data on ILI patients fulfilling the case definition, and take naso-pharyngeal specimens from a defined number of cases per week. The samples are tested in the Virology Unit at the Institut Pasteur in Phnom Penh. From each sample viral RNA was extracted and amplified by a multiplex RT-PCR detecting simultaneously influenza A and influenza B virus. Influenza A viruses were then subtyped and analyzed by hemagglutination inhibition assay. Samples collected by the ALRI system were tested with the same approach.ResultsFrom 2006 to 2008, influenza circulation was observed mainly from June to December, with a clear seasonal peak in October shown in the data from 2008.ConclusionInfluenza activity in Cambodia occurred during the rainy season, from June to December, and ended before the cool season (extending usually from December to February). Although Cambodia is a tropical country geographically located in the northern hemisphere, influenza activity has a southern hemisphere transmission pattern. Together with the antigenic analysis of the circulating strains, it is now possible to give better influenza vaccination recommendation for Cambodia.

First identified in 2001, human metapneumovirus (HMPV) is a novel pathogen and causative agent of acute respiratory tract infection. Re-infection with HMPV is common, and currently there is no available vaccine against HMPV infection. Two genotypes of HMPV have been identified, A and B, both of which can be divided further into at least two distinct sub-genotypes. Here we report the results of the first study to investigate the genetic variability of HMPV strains circulating within Cambodia. The overall incidence of HMPV infection amongst an all-ages population of patients hospitalised with ALRI in Cambodia during 3 consecutive years, between 2007 and 2009, was 1.7%. The incidence of HMPV infection was highest amongst children less than 5 years of age, with pneumonia or bronchopneumonia the most frequent clinical diagnoses across all age groups. The incidence of HMPV infection varied annually. As anticipated, genetic diversity was low amongst the conserved F gene sequences but very high amongst G gene sequences, some strains sharing as little as 56.3% and 34.2% homology at the nucleotide and amino acid levels, respectively. Simultaneous co-circulation of strains belonging to the HMPV sub-genotypes B1, B2 and lineage A2b, amongst patients recruited at 2 geographically distinct provincial hospitals, was detected. Sub-genotype B2 strains were responsible for the majority of the infections detected, and a significant (p=0.013) association between infection with lineage A2b strains and disease severity was observed.