Prognosis

Patients typically present with non-specific symptoms, such as fever, headache, and myalgia, in the first week of illness which may then progress to severe haemorrhagic signs or neurological disease in the second week. Approximately 20% to 30% of patients progress to the more severe form of disease, which is often fatal.[2][3][4][6] Bacterial infection may also complicate the disease process in the second week.[3]

Mortality rates of the SAHFs are between 16% and 30%.[2][3][4][5][6][34] With good supportive care this may be reduced, although no clinical studies have been conducted in this area. 

In Argentine haemorrhagic fever, treatment with immune plasma reduces mortality rates from 16% to approximately 1%. Immune plasma has not been studied in the other SAHFs. Of those patients who receive immune plasma and survive the disease, 10% will go on to develop a condition called late neurological syndrome (LNS). LNS develops after a symptom free period following recovery and is characterised by febrile episodes, cerebellar signs, and cranial nerve palsies. Cerebrospinal fluid analysis, which is generally normal during the acute disease period even in the context of neurological signs, demonstrates an elevated white cell count (predominantly lymphocytes) and high antibody titres to Junin virus.[4][5] LNS has not been witnessed in patients surviving Argentine haemorrhagic fever who did not receive any specific therapy, although a case has been described in a patient receiving ribavirin.[4] The pathogenesis of LNS is not well understood, but it typically begins to resolve in a matter of days but may take up to 4 months for complete resolution of symptoms.[49]​[50][51] A few patients with severe presentations have been described to have persistent neurological sequelae.[52]

There is no evidence from clinical studies that ribavirin reduces mortality in patients with SAHF;​​ however, it does appear to have an antiviral effect and, if administered early, may be of benefit to patients with SAHFs.[4]​[9]​

Patients who survive Argentine haemorrhagic fever often have a prolonged convalescent period of up to 3 months, during this time patients may experience weakness, hair loss, irritability, and memory impairment.[4][34] The convalescent phase of Bolivian haemorrhagic fever may last up to 2 months, during which time patients may complain of fatigue, dizziness, and hair loss.[2] There is little information regarding the convalescent period for the other SAHFs.

Patients who survive one of the SAHFs are thought to be immune to re-infection with that specific virus. No cases of re-infection have been described. Cross reactivity of antibodies between the SAHFs has not been described, but the Candid#1 vaccine for Argentine haemorrhagic fever has been demonstrated to provide protection against Bolivian (Machupo) haemorrhagic fever in non-human primate studies.[2]

Virus persistence has not been well described in survivors of the SAHFs. Junin virus has been isolated from blood, urine and mother’s breast milk during the acute phase of the disease, but there is no documentation of virus identification in bodily fluids in the convalescent or post-convalescent period.[5]​ Sexual transmission has been described in the context of Argentine haemorrhagic fever, although remains a rare event.[53] It has not been described in the context of the other SAHFs, but this may be related to the relatively few cases reported for some diseases. In one case of community transmission of Venezuelan haemorrhagic fever, a housewife developed symptoms 19 days following her husband being admitted to hospital with Venezuelan haemorrhagic fever. The husband was admitted for 7 days and then discharged, 12 days later his wife developed a fatal Venezuelan haemorrhagic fever.[6] It is unclear whether his wife became infected during his acute illness or the convalescent period.

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