History and exam

Key diagnostic factors

common

presence of risk factors

Living or working in or arrival from an endemic area in the past 16 days (commonly rural areas), occupational exposure, exposure to rodent host, or contact with an infected person.

fever ≥37.5°C

Presenting sign in approximately 90% of patients, and is often >38°C.[2][3][5][6][7]

bleeding (gums, epistaxis, gastrointestinal, metrorrhagia)

Bleeding is present in approximately 20% to 30% of patients with SAHF.[2][4][5][6] A case series of Venezuelan haemorrhagic fever reported bleeding from the gums in 52% of cases.[6]

The gums may be congested and may bleed spontaneously or when gentle pressure is applied. Bleeding from the gastrointestinal tract, such as melaena, rectal bleeding, or haematemesis, may develop later in the disease.[5][6] Metrorrhagia is also common in women.[5]

Bleeding usually occurs during the second week of illness.

petechiae

Petechiae of the soft palate, axillae, and across the upper chest and arms are frequently described in the context of SAHFs,​​​​ although a case series of Venezuelan haemorrhagic fever reported a frequency of only 16%.[2]​​[4][5][6]

Usually develops during the first week of illness.

uncommon

conjunctivitis

Conjunctival injection and peri-orbital oedema have been described for Argentine, Brazilian, and Venezuelan haemorrhagic fevers, where in the latter a case series reported a prevalence of approximately 15%.[4][5][6][9]

Other diagnostic factors

common

malaise

Malaise is an early presenting symptom and may occur with other non-specific symptoms in the first few days of the disease.[2][4][5][6]​ A case series of Venezuelan haemorrhagic fever reported malaise in 74% of cases.[6]

headache

An early presenting symptom which often occurs with other non-specific symptoms.​[2][4][5][6]​​ A case series of Venezuelan haemorrhagic fever reported headache in 58% of cases.[6]

arthralgia

An early presenting symptom which often occurs with other non-specific symptoms.[2][5][6] A case series of Venezuelan haemorrhagic fever reported arthralgia in 52% of cases.[6]

myalgia

An early presenting symptom which often occurs with other non-specific symptoms, often focused around the lower back.[2][4][5][6] A case series of Venezuelan haemorrhagic fever reported myalgia in 30% of cases.[6]

abdominal pain

May develop towards the end of the first week of symptoms.[2][5][6] A case series of Venezuelan haemorrhagic fever reported abdominal pain in 30% of cases.[6]

nausea/vomiting

May develop towards the end of the first week of symptoms.[2][5][6] A case series of Venezuelan haemorrhagic fever reported vomiting in 34% of cases.[6] Features of dehydration may be present on physical examination in those with severe vomiting.[5][6]

diarrhoea

May develop towards the end of the first week of symptoms.[2][5][6] Tends to be mild rather than profuse.[5] A case series of Venezuelan haemorrhagic fever reported diarrhoea in 27% of cases.[6] Features of dehydration may be present on physical examination in those with severe diarrhoea.[5][6]

lymphadenopathy

Lymphadenopathy has been described for the SAHFs with a prevalence of 23% in a case series of Venezuelan haemorrhagic fever.[4][5][6][9]

neurological symptoms (e.g., confusion, ataxia, seizures)

Approximately 20% to 30% of patients progress to severe neurological symptoms including seizures.[2][4][5][6] A case series of Venezuelan haemorrhagic fever reported a prevalence of seizures of 18%.[6]

Neurological signs carry a poor prognosis.

Usually occurs during the second week of illness.

uncommon

sore throat

More common in Venezuelan haemorrhagic fever, with prevalence of 36% in one case series.[6] Not common in Argentine haemorrhagic fever.[5]

cough

A case series of Venezuelan haemorrhagic fever reported cough in 20% of cases.[6] Rarely seen in Argentine haemorrhagic fever and not reported in Bolivian haemorrhagic fever.[2][4][5]

prostration/coma

Has been reported for Argentine, Venezuelan, and Bolivian (Machupo) haemorrhagic fevers.[2][4][5][6] It is not a common occurrence and often occurs in the terminal stages of the disease.[3][4][5] Features of shock may also be present in the later stages of the diseases with profound hypotension.[2][5][6]

Risk factors

strong

occupational exposure

Agricultural workers in endemic regions are at highest risk as the rodent vectors often live in the long grasses at the edge of fields.[2][3][5][6]

Healthcare workers in contact with infected patients are at risk, but less than in filoviral haemorrhagic fevers. There have been reports of nosocomial infection in Bolivian haemorrhagic fever (Machupo virus), and occasional reports in Argentine haemorrhagic fever (Junin virus).[2][5] There have been no reports of nosocomial transmission for Chapare virus infection, Brazilian haemorrhagic fever (Sabia virus), or Venezuelan haemorrhagic fever (Guanarito virus),​​ although this may be due to limited case numbers, particularly in the context of Chapare virus infection.[6][8]​

Laboratory workers should also be considered at risk, particularly in the context of Argentine, Bolivian, and Brazilian haemorrhagic fevers.[9][10]​​ Although experience is somewhat limited, laboratory exposure has been reported in Brazilian haemorrhagic fever both in Brazil and in the US.[9]

exposure to relevant rodent species

Rodent species involved in the transmission of SAHF are more commonly found in rural areas (e.g., long grass areas at the edges of fields).

Transmission to humans is through aerosolisation of mucous membrane contact with infected rodent excreta or urine.

Predominant rodent species is Calomys musculinus(drylands vesper rat) for Argentine haemorrhagic fever, but also Calomys laucha (small vesper mouse), Akodon azarae (Azara’s grass mouse), and Oryzomys flavescens(yellow pygmy rice rat);​​Zygodontomys brevicauda (short-tailed cane rat) for Venezuelan haemorrhagic fever;​​ and predominantly Calomys callosus (large vesper mouse) for Bolivian haemorrhagic fever.[2][3]​​​[5][6][19]

The natural host for Brazilian haemorrhagic fever and Chapare virus infection is unknown, but presumed to be rodent.[8][9]

adult males

The incidence of well-described SAHFs is significantly higher in adult males compared with females. This is likely secondary to a higher exposure risk because men, more so than women, undertake agricultural work in the fields.[2][5][6]

weak

contact with infected person

Transmission to close contacts has been described in relation to Bolivian haemorrhagic fever and occasionally in the context of Argentine haemorrhagic fever and Venezuelan haemorrhagic fever.[2][5][6] Likely associated with very few cases, and not described in Chapare virus infection or Brazilian haemorrhagic fever.

dwelling in endemic area

Only when exposure to the rodent vector population occurs.

Rodents involved in the transmission of SAHF are more commonly found in rural areas (e.g., long grass areas at the edges of fields), and are rarely found in or around human dwellings in urban areas,​​ except in the case of Bolivian haemorrhagic fever where a cluster of cases occurred in small towns following invasion of the towns by Calomys callosus.[5][6]​​[16]​​

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