Re-emergence of Bolivian hemorrhagic fever.

In July and August 1994, an outbreak of Bolivian hemorrhagic fever (BHF) occurred among an extended family living in the city of Magdalena (1994 population estimates 5,300), Itenez Province, Department of Beni, Bolivia (see map). BHF, caused by the Machupo arenavilus, is known to be endemic only in Bolivia. The principal reservoir of the Machupo virus is the small rodent Calomys callosus. This outbreak of BHF affected five of seven family members and two other relatives. The index case was the head of the household, who initially reported symptoms starting 4 July. He was admitted to Magdalena hospital on 10 July with suspected salmonellosis and remained there until the 12th; he was readmitted on 14 July, remaining until the 20th. Based on reports from family contacts, a 10-year-old daughter became symptomatic between 25 July and 2 August, while her mother became symptomatic between 3 August and 6 August. The other four patients fell ill between 8 and 12 August and the age of the patients ranged from 10 months to 50 years, including two males and five females. Two girls, aged 4 and 7, did not become ill. Family members developed illness characterized by fever, chills, muscle ache, cramps, asthenia, anorexia, diarrhea, dehydration and hypotension. Other signs included hemorrhagic gingivitis, epistaxis, subconjunctival hemorrhage, melena, petechiae, sanguinolent vomiting, and vaginal bleeding. Neurological symptoms were noted including tremors, convulsions, dysarthria, and obtunilation. Some cases developed an acute leukopenia (lowest noted to be 1,300/mm3) and thrombocytopenia (lowest noted 72.000/mm 3). Six of the seven patients died. The deaths occurred between 15 and 18 August, four of them in the city of Trinidad, where the patients had been transferred and hospitalized. Laboratory studies performed on serum and tissue specimens from decedents confirmed the diagnosis of BHF by isolation of Machupo virus and detection of viral antigen in all five patients for whom specimens were available; the survivor developed enzyme-linked immunosorbent assay (ELISA) immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies to Machupo virus. The laboratory diagnosis based on the detection of antigen and antibodies was confirmed less than 48 hours after its initiation. Preliminary epidemiological studies suggest that the index case (a man of 29 years) was infected outside Magdalena and possibly provided a source of exposure to Machupo virus for other family members. The onset of his illness began 9 days after his return to that city after working 1 month on a cattle ranch, with brief stopovers at other ranches or rural "estancias" on his way home. The family's initial contact with him during his illness occurred on 12 July when they stayed with him for 2 days during his hospitalization. The daughter and the mother were possibly infected by direct virus spread from the index case or indirect contact through contaminated fomites. The other two children may have been infected by the index case; however, the possibility that they represent cases of secondary transmission from person to person within the family cannot be excluded. A niece had contact with the family only on 24 or 25 July for a period of no more than one hour. The remaining case was the 50 year old grandmother, for whom the reported date of onset of symptoms was between 8 August and 11 August. Although a non-resident of Magdalena, she may have been infected with Machupo virus when taking care of the index case or by exposure to a second case among the other family members. During or before the outbreak, no suspected cases of BHF had been reported in Magdalena. Subsequently, a 34-year-old man with symptoms typical of BHF that began on 28 August died on 5 September in Cochabamba, Bolivia; he was potentially infected in rural areas surrounding Magdalena or while travelling to ranches outside Magdalena. On September 3, a 52-year-old agricultural worker form Poponas, El Beni Department, developed a febrile hemorrhagic illness; on September 11, he was admitted to a hospital in Trinidad, El Beni Department (see map). On September 13, intravenous ribavirin therapy was initiated for a presumptive diagnosis of BHF, and the patient recovered. The diagnosis of BHF was confirmed by detection of viral antigen and virus isolation from the sera of both patients.