Key Diagnostic Tests.

Infection has a slow onset with fever, malaise, headache and muscular pains. Petechiae (blood spots) on the upper body and bleeding from the nose and gums are observed when the disease progresses to the hemorrhagic phase.

No convenient assays are available. Diagnosis in endemic areas is patchy and often fails to differentiate it from other fevers and diagnosis often depends upon discovering the animal vector in the course of an outbreak.

Isolation of the virus requires Biosafety Level 4 facilities.

Symptoms and effects.

The disease has an incubation period of 7-16 days and the onset of symptoms is relatively slow. The first symptoms are not very specific (fever, malaise, headache, muscular pains, anorexia, nausea, vomiting). The face may be flushed and their may an enanthema ( reddening) of the throat that does not hurt. Nosebleeds (epistaxis) and vomiting of blood (hematemesis) are commoner in the early stages of Bolivian HF than Argentinian HF. Between the third and fifth day the patient dehydrates and blood pressure, urination is infrequent and the heart slows (bradycardia). The hemorrhagic phase of the disease is signalled by the appearance of petechiae (blood spots) on the upper trunk and the oral mucosa (the moist tissues of the mouth). Bleeding begins to occur from the nose, gums, stomach, and intestine. Severe cases lose enough blood to go into hypotensive shock and have a neurological crisis. Neurological symptoms are more marked in Argentinian hemorrhagic fever and this can be used as a differential test at the early stages of the disease. Fatalities can be as low as 3% and as high as 30% of those infected.

Medical and Physical Countermeasures.

Vaccination (Immunoprophylaxis)

The Candid-1 vaccine against Junin virus provides some protection against Machupo virus.

 Specific Therapy

Ribavirin is under investigation for treatment of at risk groups. It is effective against the closely-related Junin virus.

Supportive care

Minimize intrusive care to protect a weakened vascular bed. Attempt replacement therapy only in the case of severe hemorrhage. Fluid infusion to deal with dehydration is often counterproductive.

Decontamination

The virus is killed by UV radiation, drying, 1% sodium hypochlorite, or 2% glutaraldehyde.

Agent Properties and Potential Uses

The virus can be spread by aerosols and person-to-person transmission has been reported. The virus is carried by rodents, especially mice of the genus Callomys and is stable in their droppings. Typically the virus is inhaled, but it is also possible that it may entered through small abrasions or cuts in the skin.

The relatively slow onset of the disease with its unspecific symptoms that may delay diagnosis, coupled with its debilitating hemorrhagic phase make the virus a potentially serious agent.

Terrorist Acquisition and Attempted Use.

• None confirmed.