Argentine hemorrhagic fever

Junín virus

Argentine hemorrhagic fever (AHF), known locally as mal de los rastrojos, is a hemorrhagic fever and zoonotic infectious disease occurring in Argentina. It is caused by the Junín virus (an arenavirus, closely related to the Machupo virus, causative agent of Bolivian hemorrhagic fever). Its vector is a species of rodent, the corn mouse (Calomys musculinus).

Epidemiology
The endemic area of AHF covers approximately 150,000 km², compromising the provinces of Buenos Aires, Córdoba, Santa Fe and La Pampa, with an estimated risk population of 5 million.

The vector, a small rodent known locally as ratón maicero, suffers from chronic asymptomatic infection, and spreads the virus through its saliva and urine. Infection is produced through contact of skin or mucous membranes, or through inhalation of infected particles. It is found mostly in people who reside or work in rural areas; 80% of the affected are males between 15 and 60 years of age.

Clinical aspects
AHF is a grave acute disease which may progress to recovery or death in 1 to 2 weeks. The incubation time of the disease is between 10 and 12 days, after which the first symptoms appear: fever, headaches, weakness, loss of appetite and will. These intensify less than a week later, forcing the infected to lie down, and producing stronger symptoms such as vascular, renal, hematological and neurological alterations. This stage lasts about 3 weeks.

If untreated, the mortality of AHF reaches 15–30%. The specific treatment includes plasma of recovered patients, which, if started early, is extremely effective and reduces mortality to 1%. Ribavirin has also shown some promise in treating arenaviral diseases.

The disease was first detected in the 1950s in the Junín Partido in Buenos Aires, after which its agent, the Junín virus, was named upon its identification in 1958. In the early years, about 1,000 cases per year were recorded, with a high mortality rate (more than 30%). The initial introduction of treatment serums in the 1970s reduced this lethality.

Vaccine
The Candid #1 vaccine for AHF was created in 1985 by Dr. Julio Barrera Oro, of the Argentine Dr. Julio Maiztegui National Institute of Human Viral Diseases, but commercial laboratories would not produce it. The vaccine was manufactured by the Salk Institute in the United States, and became available in Argentina since 1990.

Candid #1 has been applied to adult high-risk population and is 95.5% effective. On 29 August 2006, the Maiztegui Institute obtained certification for the production of the vaccine in Argentina. A vaccination plan is yet to be outlined, but the budget for 2007 allows for 390,000 doses, at AR$8 each (about US$2.6 or €2). The Institute has the capacity to manufacture, in one year, the 5 million doses required to vaccinate the entire population of the endemic area.

Since 1991, more than 240,000 people have been vaccinated, achieving a great decrease in the numbers of reported cases (94 suspect and 19 confirmed in 2005).

The Junín vaccine has also shown cross-reactivity with Machupo virus and, as such, has been considered as a potential treatment for Bolivian hemorrhagic fever.