Nationwide genetic surveillance of Plasmodium vivax in Papua New Guinea reveals heterogeneous transmission dynamics and routes of migration amongst subdivided populations.

The Asia Pacific Leaders in Malaria Alliance (APLMA) have committed to eliminate malaria from the region by 2030. Papua New Guinea (PNG) has the highest malaria burden in the Asia-Pacific region but with the intensification of control efforts since 2005, transmission has been dramatically reduced and Plasmodium vivax is now the dominant malaria infection in some parts of the country. To gain a better understanding of the transmission dynamics and migration patterns of P. vivax in PNG, here we investigate population structure in eight geographically and ecologically distinct regions of the country. A total of 219 P. vivax isolates (16-30 per population) were successfully haplotyped using 10 microsatellite markers. A wide range of genetic diversity (He=0.37-0.87, Rs=3.60-7.58) and significant multilocus linkage disequilibrium (LD) was observed in six of the eight populations (IAS=0.08-0.15 p-value<0.05) reflecting a spectrum of transmission intensities across the country. Genetic differentiation between regions was evident (Jost's D=0.07-0.72), with increasing divergence of populations with geographic distance. Overall, P. vivax isolates clustered into three major genetic populations subdividing the Mainland lowland and coastal regions, the Islands and the Highlands. P. vivax gene flow follows major human migration routes, and there was higher gene flow amongst Mainland parasite populations than among Island populations. The Central Province (samples collected in villages close to the capital city, Port Moresby), acts as a sink for imported infections from the three major endemic areas. These insights into P. vivax transmission dynamics and population networks will inform targeted strategies to contain malaria infections and to prevent the spread of drug resistance in PNG.

Hepatitis C virus infections in the Democratic Republic of Congo exhibit a cohort effect.

The prevalence and genetic diversity of hepatitis C virus (HCV) and human pegivirus (HPgV) in many regions of sub-Saharan Africa is poorly characterized, including in the Democratic Republic of Congo--the largest country in the region and one of the most populous. To address this situation we conducted a molecular epidemiological survey of HCV and HPgV (previously named GB Virus C or hepatitis G virus) in samples collected in 2007 from 299 males from the DRC, whose ages ranged from 21 to 71 years old. Samples were tested for the presence of HCV antibodies by ELISA and reactive samples were subsequently tested for HCV RNA using RT-PCR in which both the HCV Core and NS5B genome regions were amplified. Remaining samples were tested for HPgV RNA and the HPgV NS3 genome region of positive samples was amplified. For HCV, 13.7% of the samples were seropositive (41/299) but only 3.7% were viremic (11/299). HPgV RNA was found in 12.7% (33/259) of samples. HCV viremia was strongly associated with age; the percentage of samples that contained detectable HCV RNA was ~0.5% in those younger than 50 and 13% in those older than 50. Our study represents the first systematic survey of HCV genetic diversity in the DRC. HCV sequences obtained belonged to diverse lineages of genotype 4, including subtypes 4c, 4 k, 4 l and 4r, plus one unclassified lineage that may constitute a new subtype. These data suggest that HCV in the DRC exhibits an age 'cohort effect', as has been recently reported in neighbouring countries, and are consistent with the hypothesis that HCV transmission rates were higher in the mid-twentieth century, possibly as a result of parenteral, iatrogenic, or other unidentified factors. Different HCV subtypes were associated with individuals of different ages, implying that HCV infection in the DRC may have arisen through multiple separate HCV epidemics with different causes.