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To strengthen the laboratory diagnostic capacity for Ebola virus disease (EVD) in the remote areas of Guinea, we deployed a mobile field laboratory and implemented reverse transcription loop-mediated isothermal amplification (RT-LAMP) for postmortem testing. We tested 896 oral swab specimens and 21 serum samples, using both RT-LAMP and reverse transcription-polymerase chain reaction (RT-PCR). Neither test yielded a positive result, and the results from RT-LAMP and RT-PCR were consistent. More than 95% of the samples were tested within 2 days of sample collection. These results highlight the usefulness of the RT-LAMP assay as an EVD diagnostic testing method in the field or remote areas.

Based on empiric surveillance data, the incidence of human Lassa fever (LF) cases in Guinea and other West African countries has been reported to increase during the dry season compared to the rainy season. To investigate possible links with the ecology of the rodent reservoir of the virus, we conducted a 2-year longitudinal survey of Mastomys natalensis in a region of high human Lassa virus (LASV) seropositivity in Guinea. Standardized rodent trapping with similar trapping efforts between seasons was performed in three villages and 53.5% (601/1123) of the animals were identified as M. natalensis using morphometric and molecular criteria. Mean trapping success (TS) of M. natalensis was always higher inside houses than in proximal cultivations. In the dry season, mean TS increased 2-fold inside houses and decreased up to 10-fold outside (p < 0.0001), suggesting aggregation of rodents inside houses due to restricted food supply. 14.5% (80/553) of M. natalensis were tested positive for Lassa virus by reverse transcription-polymerase chain reaction (RT-PCR; range, 5%-30%) and prevalence of the virus was two to three times higher in rodents captured in the rainy season than in the dry season (p < 0.05). Inside houses, however, the LASV prevalence fluctuated nonsignificantly with season. These data suggest that in Guinea the risk of LASV transmission from rodents to humans is present both in the rainy and the dry season, reflected by the occurrence of LF cases throughout the year. In the dry season, however, the increased risk of humans encountering Mastomys and their excreta inside of houses may result in an increase of human Lassa fever cases.

PCR screening of 1,482 murid rodents from 13 genera caught in 18 different localities of Guinea, West Africa, showed Lassa virus infection only in molecularly typed Mastomys natalensis. Distribution of this rodent and relative abundance compared with M. erythroleucus correlates geographically with Lassa virus seroprevalence in humans.

The Murid rodent diversity has been sampled following the 9th Meridian in the east of Guinea from the forest region to Sudanian savannas of southern Mali. This represents the first small mammals survey in North Guinea. Murid diversity patterns have been researched using correspondence analysis and faunal comparisons. A difference between southern forest communities and northern ones is observed. Mastomys natalensis is found only in houses in southern Guinea while in the north it is found in all sampled habitats. M. erythroleucus is absent from the forest zone, but found from the ecotone forest-savanna to the north, and it seems that this species never enter houses. Implications for Lassa fever transmission are discussed.