O n g O i n g r u b e l l a O u t b r e a k i n b O s n i a a n d H e r z e g O v i n a , M a r c H -J u ly 2 0 0 9 -p r e l i M i n a r y r e p O r t A Novo (ano@who.ba) 1 ,

Introduction Even though hepatitis B is endemic in the Lao PDR, the understanding of the epidemiology of hepatitis B infection is incomplete. This article reviews the available literature about hepatitis B seroprevalence, risk factors and genotypes in the Lao population in order to provide an up-to date summary of the HBV epidemiology in the Lao PDR, identify knowledge gaps and provide public health recommendations. Methods Using PubMed/Medline and ScienceDirect, all studies reporting the prevalence of hepatitis B markers or genotype distribution in the Lao PDR published were systematically reviewed. Results The 21 studies included focused on the general population, blood donors, women, children, health care workers and garment factory workers. The studies varied extensively in sample size, target population, methods, study location and time periods. The prevalence of the hepatitis B surface antigen (HBsAg) in blood donors was reported to be 8.7%-9.6% in 2003-2006. In the years 2011-2012, the reported HBsAg prevalence among women (including pregnant women) ranged from 0%-9.5% and among children aged 5-9 years from 1.7%-8.7%, depending on study location and age. The majority of strains characterized in Lao PDR belonged to genotypes B and C. Conclusion Studies displayed considerable heterogeneity in populations, design and laboratory methods. A high HBsAg prevalence was reported in adults including pregnant women. Low infant vaccination coverage and compromised vaccine immunogenicity were found. Only two studies focused on HBV in risk populations, emphasizing the need for further studies to characterize hepatitis B epidemiology in potentially vulnerable groups. Hepatitis B infection continues to represent a substantial public health threat in the Lao PDR and needs to be monitored to inform health authorities and to counteract over-burdening of the health care system. In order to end mother to child transmission, vaccination coverage with the hepatitis B birth dose should be increased.

Background: Respiratory syncytial virus (RSV) is one of the main viral pathogens causing acute respiratory infections in children under 5 years of age, but has seldom been studied in Central African Republic (CAF). Methods: Taking advantage of the national influenza surveillance network in CAF, a total of 3903 children under 5 years matching the influenza-like illness (ILI, 68.5%) or severe acute respiratory infection (SARI, 31.5%) case definitions were recruited from January 2015 to December 2018 to determine annual RSV prevalence, seasonality and disease severity as well as to characterise RSV strains. The presence of RSV viral RNA in nasopharyngeal samples was assessed by RT-PCR, followed by RSV-A and -B typing and Sanger sequencing. Results: RSV incidence was significantly higher in infants < 6 months (13.4%), in hospitalized children (13.3% vs 5.5%) and in male patients (9.5% vs 6.4%). An overall prevalence of RSV of 8.0% in the period of 2015-2018 was shown, with significant annual (6.4%-10.6%) and seasonal (12.7% in rainy season vs 3.0% in dry season) fluctuations. While RSV seasons in 2015, 2016 and 2018 were relatively similar, 2017 showed deviations from the overall patterns with significantly higher RSV incidence and peak incidence 3-5 months earlier. Concomitant circulation of RSV-A and RSV-B with an alternating predominance of RSV-A and RSV-B strains and temporal RSV-A genotype replacement from NA1 to ON1 were observed. Conclusion: This study represents the first in-depth epidemiological analysis of RSV in CAF and provides first insights into RSV burden, genetic diversity and seasonality in the country.

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