Haemorrhagic fevers in Bolivia: origins, reservoirs, transmission and guidelines

Background

Machupo virus (MACV) is a mammarenavirus and was first identified in 1963 from a patient who died following a haemorrhagic fever illness in Beni department, Bolivia. In 2003, Chapare virus (CHAPV), also a mammarenavirus, was discovered in a small cluster of patients in Cochabamba municipality, Bolivia. Human infection with both viruses occurs after exposure to infected wild native rodents in Bolivia.

Epidemiology

MACV is endemic within a small geographic region of Bolivia, with most recent outbreaks reported from the Beni department in the north-east.

The first outbreak of CHAPV involved a small cluster of cases from a rural area near the Chapare River, close to Cochabamba. Cases of CHAPV have been predominantly reported from rural areas of Bolivia including Cochabamba and La Paz.

There is no evidence of either of these viruses occurring in countries outside of Bolivia.

Transmission

Humans are infected by MACV and CHAPV through mucosal exposure, aerosolised excretions or secretions, or by direct contact of broken skin with infectious material from infected rodents. Human-to-human transmission is rare and may occur via direct contact with the blood, tissues or body fluids from an infected patient. Nosocomial transmission has been documented for both viruses suggesting a risk to healthcare and laboratory workers exposed to body fluids from infected patients.

Most cases occur in those living in endemic areas with occupational exposures occurring in those involved in agricultural processes. These viruses cause seasonal outbreaks with the highest incidence correlating with rodent migration in the rainy season, although sporadic cases can occur throughout the year.

Clinical features

The incubation periods range from 3 to 19 days but can be up to 21 days. The onset of the clinical disease is non-specific, with malaise, chills, joint pains, muscle pains and fever. Patients may progress to develop constitutional, gastrointestinal, cardiovascular and neurologic signs and symptoms several days later. Symptoms reported include:

• nausea
• vomiting
• abdominal pain
• constipation or mild diarrhea.
• photophobia
• poor co-ordination and balance disturbances
• seizures
• confusion
• coma

Haemorrhagic (bleeding) manifestations can occur in cases caused by either virus, ranging from mild to severe. Bruising, bleeding gums, nosebleeds, gastrointestinal bleeding, haemoptysis (coughing up blood), and haematuria (blood in the urine) may be seen. About one-third of cases develop life-threatening haemorrhagic or neurologic complications within a week of their initial symptoms.

Case-fatality rates (CFR) for MACV have varied between outbreaks but are estimated to be 25-35% or higher depending on the specific circumstances of the outbreak. The overall CRF for CHAPV across documented outbreaks is estimated to be around 50%.

Diagnosis

Any suspected cases of MACV or CHAPV should be discussed with local infection specialists. In the UK, clinicians who suspect that a patient may have MACV or CHAPV should seek urgent advice from the UK Health Security Agency’s (UKHSA) Imported Fever Service (IFS) on 0844 778 8990.

The IFS operates 24/7 and provides advice on risk assessment, immediate management and infection control.

The IFS will also coordinate urgent testing at UKHSA’s Rare and Imported Pathogens Laboratory (RIPL), Porton. 

IFS will also advise on sample collection precautions and transport requirements.

See also VHF sample testing advice

Treatment

There are currently no licensed vaccines or specific antivirals to treat MACV or CHAPV. Treatment is therefore supportive. This includes maintaining good fluid and electrolyte balance, as well as managing diarrhoea, vomiting, fever and pain with medications and blood transfusions as required.

Guidelines

The UK has guidelines for managing viral haemorrhagic fevers. Clinicians should be alert to the possibility of haemorrhagic fever viruses in patients returning from rural areas in Bolivia with symptoms and /or signs compatible with a VHF. Suspected cases should be discussed urgently with the IFS.

Prevention and control

Patients suspected of having MACV or CHAPV should be managed as suspected viral haemorrhagic fever (VHF) cases. Measures for prevention of secondary transmission of both MACV and CHAPV are similar to those used for other haemorrhagic fever viruses and focus on avoiding contact with infected body fluids. Suspected cases must be immediately isolated and assessed using appropriate VHF assessment personal protective equipment.

See the ACDP algorithm and guidance on management of patients for further information.

Cases imported into the UK

There have been no reported cases of MACV or CHAPV in the UK.