Argentine Haemorrhagic fever: origins, reservoirs, transmission and guidelines
Junin virus causes Argentine Haemorrhagic fever, an acute viral haemorrhagic fever (VHF).
Background
Argentine haemorrhagic fever (AHF) is caused by Junin virus, a member of the arenavirus family. Junin virus was first discovered in 1958 in remote agricultural areas of Argentina, although the syndrome was described several years earlier. AHF is endemic to the low grassland areas known as the Pampas region of Argentina where the animal reservoir, the Calomys rodent, is prevalent. This region covers the provinces of Buenos Aires, Cordoba, Sante Fe and La Pampa.
Until vaccination was introduced for populations at greatest risk in 1990, up to 600 cases were diagnosed each year in grassland areas of Argentina.
AHF cases rarely occur outside of Argentina. There has been one reported case of AHF in Belgium in a patient who was thought to have acquired the infection in the city of Perez, Santa Fe, Argentina, before travelling to Brussels and becoming unwell.
AHF caused by Junin virus is designated as a high consequence infectious disease (HCID) in the UK.
Natural reservoir
Junin virus is a zoonotic virus (can be transmitted from animals to humans), which is spread by the corn mouse (Calomys species) that live along the margins of cultivated fields. Once infected, rodents excrete the virus in their urine and droppings. Human exposure to Junin virus most commonly occurs during the harvest season (between April and July).
Transmission
Humans are infected by Junin virus through mucosal exposure, aerosolised excretions or secretions, or by direct contact of broken skin with infectious material from infected rodents. The majority of cases are from those living in endemic areas, exposed through their occupation. Human-to-human transmission is very rare and may occur via direct contact with the blood, tissues or body fluids from an infected individual. Nosocomial transmission has also been documented suggesting a risk to healthcare and laboratory workers.
Symptoms
The incubation period is usually 5 to 14 days but can be up to 21 days.
The initial onset of the clinical disease is similar to many infectious diseases and usually includes:
- fever
- muscle aches and pains
- fatigue
- anorexia
- chills
- headache
Approximately 20% of patients will recover from the initial illness, while 80% will progress to a haemorrhagic fever syndrome. The initial prodromal phase of AHF lasts approximately 1 week after symptom onset and as well as the symptoms above may include:
- eye pain
- conjunctivitis and swelling around the eyes
- dizziness
- sensitivity to light
- constipation or mild diarrhoea
- petechial rash
- bleeding gums
- swollen neck glands
- blistering rash in the mouth
20 to 30% of patients then progress to the neurological-haemorrhagic phase, which can include neurological and haemorrhagic manifestations. Haemorrhagic manifestations in cases with AHF range from mild to severe, including petechiae (red spots caused by small bleeding blood vessels), bruising, bleeding gums, nosebleeds, haematomas (a collection of blood outside of the blood vessels), gastrointestinal bleeding, vaginal bleeding, haemoptysis (coughing up blood), and haematuria (blood in the urine). Neurological manifestations include confusion, tremors, seizures and coma.
Case fatality rates of up to 30% have been reported in untreated cases.
In survivors, the convalescent phase can last for several months after the acute illness. Patients may report generalised weakness, irritability, poor memory and hair loss.
Diagnosis
In the UK, clinicians who suspect that a patient may have AHF 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).
See VHF sample testing advice.
Treatment
There are no licensed drugs available to treat Argentine Haemorrhagic Fever. The mainstay of treatment is therefore supportive.
This includes:
- maintaining good fluid and electrolyte balance
- managing diarrhoea, vomiting, fever and pain with standard medications
- blood transfusions as required
- organ support such as dialysis and ventilation can improve survival in severely unwell patients
Immune plasma has been used historically but there is limited evidence for efficacy.
Ribavirin and favipiravir are antiviral drugs which are under investigation as possible treatment options but more work is needed to establish their efficacy.
Guidelines
The UK has specialist guidance on the management (including infection control) of patients with viral haemorrhagic fevers, including AHF.
The guidelines provide advice on risk assessment, testing and management of suspected VHF cases presenting to healthcare services within the UK.
Prevention and control
An approved vaccine (Candid#1) is available in Argentina and is used to protect against AHF. In Argentina, vaccination is recommended for individuals who may be exposed to Junin virus through their occupations (for example, agricultural or laboratory workers).
Avoiding contact with infected humans can help prevent infection. This includes avoiding contact with blood and other bodily fluids of those who are infected, as well as avoiding contact with contaminated items like bedding and medical equipment. In healthcare settings, infection control measures include:
- special barrier nursing procedures
- viral haemorrhagic fever (VHF) isolation precautions to isolate infected patients
- wearing personal protective equipment for contact with patients
Cases in the UK
There have been no reported cases of AHF in the UK.