From the end of 1994 to the beginning of 1995, 49 patients with hemorrhagic symptoms were hospitalized in the Makokou General Hospital in northeastern Gabon. Yellow fever (YF) virus was first diagnosed in serum by use of polymerase chain reaction followed by blotting, and a vaccination campaign was immediately instituted. The epidemic, known as the fall 1994 epidemic, ended 6 weeks later. However, some aspects of this epidemic were atypical of YF infection, so a retrospective check for other etiologic agents was undertaken. Ebola (EBO) virus was found to be present concomitantly with YF virus in the epidemic. Two other epidemics (spring and fall 1996) occurred in the same province. GP and L genes of EBO virus isolates from all three epidemics were partially sequenced, which showed a difference of 0.1% in the base pairs. Sequencing also showed that all isolates were very similar to subtype Zaire EBO virus isolates from the Democratic Republic of the Congo.
No serologic data were available from persons in Ogooue´-Ivindo Province before the first epidemic. This low percentage of seropositviity suggests that the circulation of EBO is a new phenomenon in the area, affecting mainly people living deep in the forest in temporary encampments. There are interesting demographic and ecologic differences between the sites of the first two epidemics. The disturbance of the forest integrity is one common feature between the two sites, but the one important difference is the permanence and the size of the population around Mayibout 2, which might permit the virus, once present in the area, to circulate within the human population. Both the reservoir and the vector for the EBO virus as still unknown.
It is very clear that the use of simple barrier nursing methods in even the most basic of hospital settings is sufficient to limit the spread of this disease. Nosocomial spread of infection due to the lack of recognition of the disease and the dearth of training and material available to establish simple barrier nursing remains the root cause of most of the disease observed to date. From the public health point of view, this remains a basic goal for the prevention of EHF epidemics. Preventing primary infection certainly requires the identification of risk factors and the reservoir, something that continues to elude us.