Filovirus ebola et Marburg

Risk factors for Zaire ebolavirus--specific IgG in rural Gabonese populations

BACKGROUND

In Gabon, several Ebolavirus outbreaks have occurred exclusively in the northeastern region. We conducted a large serosurvey to identify areas and populations at risk and potential demographic, clinical, and behavioral risk factors.

METHODS

Blood samples and clinical and sociodemographic data were collected from 4349 adults and 362 children in a random sample of 220 villages in the 9 provinces of Gabon. An enzyme-linked immunosorbent assay was used to detect Zaire ebolavirus (ZEBOV)-specific IgG, and thin blood smears were used to detect parasites. Logistic regression was implemented using Stata software (Stata), and a probability level of <.05 was considered to be statistically significant.

RESULTS

The prevalence of ZEBOV-specific IgG was 15.3% overall, increasing to 32.4% (P< .001) in forest areas. No sociodemographic risk factors were found, but the antibody prevalence increased linearly up to 20 years of age. Chronic arthralgia and amicrofilaremia were the only factors associated with ZEBOV seropositivity.

CONCLUSIONS

These findings confirm the endemicity of ZEBOV in Gabon and its link to the ecosystem. Human antibody positivity would appear to be to the result of exposure to contaminated fruits.

A limited outbreak of Ebola haemorrhagic fever in Etoumbi, Republic of Congo, 2005

Ebolavirus has caused highly lethal outbreaks of haemorrhagic fever in the Congo basin. The 2005 outbreak in the Republic of Congo occurred in the Etoumbi district of Cuvette Ouest Department between April and May. The two index cases were infected while poaching. The sanitary response consisted of active surveillance and contact tracing, public awareness campaigns and community mobilization, case management and safe burial practices, and laboratory confirmation. Twelve cases and ten deaths were reported (lethality 83%). A transmission tree was constructed from a sample collected by a medical team. This outbreak was remarkable by its short duration and limited size. Increased awareness among these previously affected populations and the rapid response of the healthcare system probably contributed to its extinction.

Molecular characterization of an isolate from the 1989/90 epizootic of Ebola virus Reston among macaques imported into the United States

We have determined the entire genomic sequence of the Pennsylvania strain, which was isolated along with the Virginia strain during the emergence of Ebola virus Reston in 1989/90 in the United States. Thus, either the Pennsylvania or Virginia strain, neither of which had been previously molecularly characterized, can be considered as the prototype for Ebola virus Reston. Comparative analysis showed a high degree of homology to the concomitantly analyzed and recently published Philippine strain of EBOV Reston from 1996 (Ikegami et al., Arch. Virol., 146 (2001) 2021). In comparison to EBOV Zaire, strain Mayinga, conservation could be found within the open reading frames, the 3' leader and 5' trailer region and the transcriptional signals, whereas the non-coding and intergenic regions did not show any homology. This clearly supports that EBOV Reston is a distinct species within the genus Ebola-like virus but which seems to be similar to other members with respect to transcription and replication strategies. The sequence determination provides the basis for the development of a reverse genetics system for Ebola virus Reston, which is needed to study differences in pathogenicity among filoviruses.

The glycoproteins of Marburg and Ebola virus and their potential roles in pathogenesis

Filoviruses cause systemic infections that can lead to severe hemorrhagic fever in human and non-human primates. The primary target of the virus appears to be the mononuclear phagocytic system. As the virus spreads through the organism, the spectrum of target cells increases to include endothelial cells, fibroblasts, hepatocytes, and many other cells. There is evidence that the filovirus glycoprotein plays an important role in cell tropism, spread of infection, and pathogenicity. Biosynthesis of the glycoprotein forming the spikes on the virion surface involves cleavage by the host cell protease furin into two disulfide linked subunits GP1 and GP2. GP1 is also shed in soluble form from infected cells. Different strains of Ebola virus show variations in the cleavability of the glycoprotein, that may account for differences in pathogenicity, as has been observed with influenza viruses and paramyxoviruses. Expression of the spike glycoprotein of Ebola virus, but not of Marburg virus, requires transcriptional editing. Unedited GP mRNA yields the nonstructural glycoprotein sGP, which is secreted extensively from infected cells. Whether the soluble glycoproteins GP1 and sGP interfere with the humoral immune response and other defense mechanisms remains to be determined.