Comparative analysis of West Nile virus strains isolated from human and animal hosts using monoclonal antibodies and cDNA restriction digest profiles.

Three West Nile (WN) virus strains isolated in Bangui, Central African Republic (CAR), from patients with hepatitis were analysed comparatively with the prototype WN virus strain and 7 WN strains previously isolated from birds (2 strains), mosquitoes (3 strains) and ticks (2 strains) in CAR. The comparison was based on two techniques: an epitopic analysis by indirect immunofluorescence assay using a panel of 9 monoclonal antibodies to WN virus, and an analysis of HaeIII and TaqI restriction digest profiles of cDNA to infected cell RNA. Similar results were obtained with both techniques: the 3 human strains were found to be identical to each other and identical or very close to mosquito and tick strains, whereas prototype WN virus and bird strains were significantly different from the human strains. As "classical" infections due to WN virus without hepatic involvement were also reported during the period of isolation of the arthropod strains, we concluded that the same virus subtype may have been the cause of different infection patterns. A new definition of the disease spectrum of WN virus, including the possibility of liver involvement, should be established. Clearly, the Egyptian prototype WN virus represents a different topotype. Bird strains also appear to be different from human and arthropod strains, raising the question of their transmissibility and pathogenicity for man, and of the role of birds in the natural cycle of WN virus.

An outbreak of human Semliki Forest virus infections in Central African Republic.

Semliki Forest (SF) virus was responsible for an outbreak of febrile illnesses in Bangui, Central African Republic (CAR), during October-December 1987. The virus was isolated at first from mosquitoes, mainly Aedes africanus, collected August-October in a gallery forest 100 km from Bangui. During October-December, 22 isolations of SF virus were made from serum samples collected from patients in Bangui presenting with fever, severe persistent headache, myalgia, arthralgia, and a convalescence marked by asthenia. During the same period, 8 SF virus isolates were obtained from mosquitoes collected in Bangui, mainly from Ae. aegypti. Europeans, particularly soldiers who had recently arrived from France, were affected. Antibodies to alphaviruses had been previously detected in a high proportion of resident human populations in CAR. We conclude that SF virus is a human pathogen.

Antibodies to haemorrhagic fever viruses in Madagascar populations.

Sera of 381 adult people from 5 areas in Madagascar were tested by the indirect immunofluorescence method for antibodies against Congo-Crimean haemorrhagic fever and Rift Valley fever viruses (Bunyaviridae), Ebola (strains Zaire and Sudan) and Marburg viruses (Filoviridae), and Lassa virus (Arenaviridae). The highest prevalence rate was that of Ebola virus (4.5%). As no haemorrhagic syndrome has been found associated with this virus, the possible presence of a less pathogenic, antigenically related, strain is discussed. The prevalences of Congo-Crimean haemorrhagic fever and Rift Valley viruses were very low, despite previous viral isolations from potential vectors. No serum reacted against Lassa or Marburg antigens. The results are analysed in the light of the geographical and bioecological characteristics of Madagascar, which is a true 'microcontinent' very different from the African mainland.

[Current problems of arboviruses in central Africa]. / Problèmes actuels des arboviroses en centrafrique.

19 arboviruses pathogenic for human are present in the Central African Republic (CAR) where serologic data indicate an active circulation in human population. In most cases the clinical picture of infection is mild. However 3 arbovirus were recently involved in fatal cases: in 1983 West-Nile virus has been isolated in 4 patients with hepatitis. 2 fatal cases of Yellow Fever occurred in 1985 and 1986, and from 1983 to 1986 Rift Valley Fever virus was isolated in patients who died from hemorrhagic fever. This new situation requires to carry on an epidemiological survey and studies on virus pathogenicity.