Abstract. The importance of leptospirosis in Southeast Asia was assessed in conjunction with other studies supported by the U.S. Naval Medical Research Unit No. 2 (US NAMRU-2), Jakarta, Republic of Indonesia. These included studies of hospital-based, acute clinical jaundice in Indonesia, Lao PDR, and Socialist Republic of Vietnam; nonmalarial fever in Indonesia; and hemorrhagic fever in Cambodia. Background prevalence estimates of leptospiral infection were obtained by a cross-sectional, community-based study in Lao PDR. Laboratory testing methods involved serology, microscopic agglutination test, and reverse-transcriptase polymerase chain reaction. Suggestive evidence of recent leptospiral infections was detected in 17%, 13%, and 3% of patients selected on the basis of non-hepatitis A through E jaundice, nonmalarial fever, and hemorrhagic fever (in the absence of acute, dengue viral infections). Leptospiral IgG antibody, reflective of prior infections, was detected in 37% of human sera, collected in Lao PDR. The predominant leptospiral serogroups identified from cases with clinical jaundice were Hurstbridge, Bataviae, and Icterohaemorrhagiae tonkini LT 96 69. Among the nonmalarial febrile cases, Bataviae was the most frequently recognized serogroup. Pyrogenes and Hurstbridge were the principal serogroups among the hemorrhagic fever case subjects. These findings further attest to the relative importance of clinical leptospirosis in Southeast Asia. The wide spectrum of clinical signs and symptoms associated with probable, acute, leptospiral infections contributes to the potential of significant underreporting.

BackgroundMeasles outbreaks have occurred in some countries despite supplementary immunization activities (SIA) using measles-containing vaccine with high vaccination coverage. We conducted a cross-sectional seroprevalence survey to estimate population immunity in Lao People's Democratic Republic where repeated mass immunization has failed to eliminate measles.Methods and findingsIn this nationwide multistage cluster sampling survey conducted in 2014 based on probability proportionate to size sampling, blood samples were collected from 2,135 children and adults living in 52 randomly selected villages. Anti-measles and anti-rubella IgG were measured, and IgG prevalence was calculated. We applied mathematical modelling to estimate the number of cases of congenital rubella syndrome (CRS) in 2013 that were averted by the 2011 SIA. A stability testing was applied to the MR vaccine at 4°C, 25°C, and 35°C to examine stability differences between measles and rubella vaccine components. Measles IgG prevalence was significantly lower in the target age groups (5–21 years) of the 2011 SIA using a combination vaccine for measles and rubella vaccine (MR vaccine) than in young adults (22–39 years) (86.8% [95% CI: 83.0–90.6] vs. 99.0% [98.3–99.8]; p<0.001), whereas rubella IgG prevalence was significantly higher (88.2% [84.5–91.8] vs. 74.6% [70.7–78.5]; p<0.001). In the SIA target age groups, prevalence of measles IgG, but not rubella IgG, increased with age. CRS cases prevented in 2013 ranged from 16 [0–50] to 92 [32–180] if the force of infection had remained unchanged or had been reduced by 75%, respectively. In freeze-dried conditions, the measles vaccine component was more heat sensitive than the rubella component.ConclusionsInconsistent IgG prevalence between measles and rubella in Lao PDR can be partly explained by different stability of the measles and rubella vaccine components under heat exposure. Suboptimal vaccine handling may cause insufficient immunogenicity for measles, which subsequently leads to an outbreak despite high SIA coverage, while direct evidence is lacking. Temperature monitoring of the vaccine should be conducted.

Please cite this paper as: Vongphrachanh P, Simmerman JM, Phonekeo D, Pansayavong V, Sisouk T, Ongkhamme S, Bryce GT, Corwin A, Bryant JE. An early report from newly established laboratory‐based influenza surveillance in Lao PDR. Influenza and Other Respiratory Viruses 4(2), 47–52. Background  Prior to 2007, little information was available about the burden of influenza in Laos. We report data from the first laboratory‐based influenza surveillance system established in the Lao People’s Democratic Republic. Methods  Three hospitals in the capital city of Vientiane began surveillance for influenza‐like illness (ILI) in outpatients in 2007 and expanded to include hospitalized pneumonia patients in 2008. Nasal/throat swab specimens were collected and tested for influenza and other respiratory viruses by multiplex ID‐TagTM respiratory viral panel (RVP) assay on a Luminex® 100× MAP IS instrument (Qiagen, Singapore). Results  During January 2007 to December 2008, 287 of 526 (54·6%) outpatients with ILI were positive for at least one respiratory virus. Influenza was most commonly identified, with 63 (12·0%) influenza A and 92 (17·5%) influenza B positive patients identified. In 2008, six of 79 (7·6%) hospitalized pneumonia patients were positive for influenza A and four (5·1%) were positive for influenza B. Children <5 years represented 19% of viral infections in outpatients and 38% of pneumonia inpatients. Conclusion  Our results provide the first documentation of influenza burden among patients with febrile respiratory illness and pneumonia requiring hospitalization in Laos. Implementing laboratory‐based influenza surveillance requires substantial investments in infrastructure and training. However, continuing outbreaks of avian influenza A/H5N1 in poultry and emergence of the 2009 influenza A(H1N1) pandemic strain further underscore the importance of establishing and maintaining influenza surveillance in developing countries.

BackgroundAcute respiratory infections are an important cause of morbidity and mortality worldwide, with a major burden of disease in developing countries. The relative contribution of viruses in acute lower respiratory infections (ALRI) is, however, poorly documented in Lao PDR.ObjectiveThe objective of this study is to investigate the etiology of ALRI in patients of all ages in two hospitals of Laos.MethodsMultiplex PCR/RT‐PCR methods were used to target 18 major common respiratory viruses. Between August 2009 and October 2010, samples from 292 patients presenting with ALRI were collected.Results and conclusionViruses were detected in 162 (55%) samples. In 48% (140/292) of the total ALRI cases, a single virus was detected while coinfections were observed in 8% (22/292) of the samples. The most frequent viruses were rhinovirus/enterovirus (35%), human respiratory syncytial virus (26%), and influenza viruses (13%). Parainfluenza viruses were detected in 9%, adenovirus in 6%, human metapneumovirus in 4%, coronaviruses (229E, NL63, OC43, HKU1) in 4%, and bocavirus in 3% of ALRI specimens. Most viral infections occurred in patients below 5 years of age. The distribution of viruses varied according to age‐groups. No significant correlation was observed between the severity of the disease and the age of patients or the virus species. This study provides the description of viral etiology among patients presenting with ALRI in Lao PDR. Additional investigations are required to better understand the clinical role of the different viruses and their seasonality in Laos.

BackgroundHepatitis B is regarded as a serious public health issue in Lao People's Democratic Republic (Lao PDR), a Southeast Asian country. However, disease epidemiology among the general population is not well known, and thus a nationwide cross-sectional survey for hepatitis B surface antigen (HBsAg) prevalence in children and their mothers was conducted.Methods and findingsWe applied three-stage cluster sampling using probability proportionate to size. After randomly selecting child (5 to 9 years old) and mother (15 to 45 years old) pairs from the selected villages, questionnaires and HBsAg rapid tests were conducted. Data from 965 child and mother pairs were analyzed. Multivariate logistic regression analyses were used to investigate the independent association of individual background characteristics for the odds of being HBsAg positive. In total, 17 children and 27 mothers were HBsAg positive. HBsAg prevalence was estimated to be 1.7% (95% confidence interval: 0.8%-2.6%) in children, and 2.9% (95% confidence interval: 1.7%–4.2%) in their mothers after taking sampling design and weight of each sample into account. Mother's infection status was positively associated with HBsAg positivity in children (p<0.001), whereas other potential risk factors, such as ethnicity, proximity to health centers, and history of surgery, were not. There were no significant associations between mother's HBsAg status and history of surgery, and other sociodemographic factors.ConclusionsDespite the slow implementation of the hepatitis B vaccination program, HBsAg prevalence among children and their mothers was not high in Lao PDR compared to reports from neighboring countries. The reasons for the differences in prevalence among these countries are unclear. We recommend that prevalence surveys be conducted in populations born before and after the implementation of a hepatitis B vaccination program to better understand the epidemiology of hepatitis B.