Bolivia's History With Hemorrhagic Fever: How Long Has It Been?

Bolivian Hemorrhagic Fever (BHF), also known as black typhus or Ordog Fever, is a zoonotic infectious disease caused by the Machupo virus. It was first identified in 1959 in the Beni region in northeastern Bolivia and recognised as a new epidemic infectious disease in 1962. The disease is transmitted to humans through contact with the excreta of infected rodents or by consuming contaminated food and water supplies. The large vesper mouse (Calomys callosus), a rodent indigenous to northern Bolivia, is the primary vector and reservoir for the virus. While there is no cure or vaccine for BHF, control measures such as rodent population eradication have proven effective in reducing the number of cases.

The disease was first identified in 1959/1962/1963

Bolivian Hemorrhagic Fever (BHF), also known as black typhus or Ordog Fever, is a hemorrhagic fever and zoonotic infectious disease originating in Bolivia after infection by the Machupo mammarenavirus. The disease was first identified in 1959 as a sporadic hemorrhagic illness in rural areas of Beni, Bolivia. It appeared near the Amazon River in the context of a government settlement program. Between 470 and 1000 reported cases occurred in the years up to 1962, mostly in male adults in rural areas around San Joaquin.

In 1962, BHF was recognised as a new epidemic infectious disease. By this time, the disease had spread to urban areas, which was correlated with a decrease in the domestic feline population and an increase in the rodent population. The drop in the number of cats was suspected to have been caused by overexposure to DDT, which was being used to combat malaria. This led to a mouse plague in the village of San Joaquín, where BHF was first encountered in 1962.

In 1963, a research group led by Karl Johnson identified the etiological agent of BHF as the Machupo virus, an ambisense RNA virus of the Arenaviridae family. The virus was isolated from patients with acute hemorrhagic fever in San Joaquin, Bolivia.

It is caused by the Machupo virus

Bolivian Hemorrhagic Fever (BHF), also known as black typhus or Ordog Fever, is a hemorrhagic fever and zoonotic infectious disease caused by the Machupo virus. It was first identified in 1959 as a sporadic and severe febrile illness in rural areas of the Beni department in Bolivia. The disease was first encountered in 1962 in the Bolivian village of San Joaquín, and in 1963, the Machupo virus was isolated from patients with acute hemorrhagic fever in the same village. The Machupo virus is a member of the family Arenaviridae, specifically the Tacaribe-LCMV complex, which includes other viruses such as Lassa fever, Junin, and lymphocytic choriomeningitis virus.

The Machupo virus is transmitted to humans through contact with the excreta of infected rodents, consumption of contaminated food or water, or exposure to the secretions and blood of infected individuals. The large vesper mouse (Calomys callosus), a rodent indigenous to northern Bolivia, is the primary vector for the virus. These infected mice are asymptomatic and shed the virus in their excreta. While human-to-human transmission of BHF is possible, it is believed to be rare.

The infection caused by the Machupo virus has a slow onset, with initial symptoms including fever, malaise, headache, and myalgia. As the disease progresses, typically within seven days of onset, it enters the hemorrhagic phase, characterised by petechiae (blood spots) on the upper body and bleeding from the nose and gums. About one-third of patients also develop severe hemorrhagic or neurologic symptoms, including tremors, delirium, convulsions, and, rarely, hypotensive shock. The mortality rate of BHF is estimated to be between 5 and 30 percent, with a recent study placing it at about 25%.

Due to its high pathogenicity, the Machupo virus requires Biosafety Level Four conditions, the highest level of biosafety precautions. While there is currently no cure or vaccine specifically for BHF, a vaccine developed for the related Junín virus, which causes Argentine hemorrhagic fever, has shown evidence of cross-reactivity to the Machupo virus. This suggests that it may be an effective prophylactic measure for individuals at high risk of infection. Additionally, individuals who survive BHF typically develop immunity to further infections.

The large vesper mouse is the primary vector and reservoir for the virus

Bolivian Hemorrhagic Fever (BHF), also known as black typhus or Ordog Fever, is a zoonotic infectious disease caused by the Machupo mammarenavirus. The disease was first encountered in 1962 in the Bolivian village of San Joaquín, though it was first identified in 1959 as a sporadic illness in rural areas of the Beni department in Bolivia.

The large vesper mouse (Calomys callosus) is a South American rodent species indigenous to northern Bolivia, Argentina, Brazil, and Paraguay. It is the primary vector and reservoir for the Machupo virus, with the virus being isolated from 25% of C. callosus in enzootically infected areas. The large vesper mouse is believed to have been responsible for the first outbreak of BHF in San Joaquín, with infected mice transmitting the virus to humans.

Infected large vesper mice are asymptomatic and can spread the virus through their excreta, which can contaminate food and water supplies. Humans can also become infected by coming into contact with the secretions and blood of infected individuals. The virus spreads horizontally between rodents, and infection of C. callosus younger than 10 days of age leads to immune tolerance and persistent viremia.

The large vesper mouse's role as the primary vector and reservoir for the Machupo virus has important implications for controlling and preventing BHF outbreaks. Measures to reduce contact between the vesper mouse and humans, such as rodent control and eradication, have been effective in limiting the number of outbreaks. For example, the local eradication of C. callosus was crucial in controlling BHF outbreaks in small hamlets in Bolivia. Understanding the ecology of the rodent reservoir and virus transmission dynamics is crucial for developing effective control strategies.

While human-to-human transmission of BHF is possible, it is believed to be rare. The disease has a slow onset, with initial symptoms including fever, malaise, headache, and myalgia, which can progress to severe hemorrhagic or neurologic symptoms in about one-third of patients. The mortality rate of BHF is estimated to be between 5 and 30%.

The disease has a 5-30% mortality rate

Bolivian Hemorrhagic Fever (BHF), also known as black typhus or Ordog Fever, is a highly pathogenic disease with a mortality rate of 5-30%. The disease was first identified in 1963 as an RNA virus of the Arenaviridae family, though it was first encountered a year earlier in 1962 in the Bolivian village of San Joaquín.

The mortality rate of BHF is relatively high compared to other diseases. For reference, the case-fatality rate for dengue—a mosquito-borne disease found in Asia, Africa, and the Americas—is less than 10%. Ebola, one of the most notorious VHF viruses, has had outbreaks with case-fatality rates of up to 90%.

The high mortality rate of BHF can be attributed to its pathogenicity and the lack of a cure or vaccine for the disease. BHF requires Biosafety Level Four conditions, the highest level. While there is no cure or vaccine for BHF, a vaccine developed for the genetically related Junín virus that causes Argentine hemorrhagic fever has shown evidence of cross-reactivity to the Machupo virus that causes BHF. This may be an effective prophylactic measure for people at high risk of infection.

There is no cure or vaccine for the disease

Bolivian Hemorrhagic Fever (BHF), also known as black typhus or Ordog Fever, is a hemorrhagic fever and zoonotic infectious disease originating in Bolivia after infection by the Machupo mammarenavirus. BHF was first identified in 1959 as a sporadic hemorrhagic illness in rural areas of Beni, Bolivia, and was recognised as a new epidemic infectious disease in 1962. The disease was first encountered in 1962 in the Bolivian village of San Joaquín.

There is currently no cure or vaccine for BHF. However, a vaccine developed for the genetically related Junín virus, which causes Argentine hemorrhagic fever, has shown evidence of cross-reactivity to the Machupo virus, and may therefore be an effective prophylactic measure for people at high risk of infection. Post-infection, those who survive BHF are usually immune to further infection.

The infection has a slow onset, with fever, malaise, headache, and myalgia, very similar to Malaria symptoms. Petechiae (blood spots) on the upper body and bleeding from the nose and gums are observed when the disease progresses to the hemorrhagic phase, usually within seven days of onset. Severe hemorrhagic or neurologic symptoms are observed in about one-third of patients. Neurologic symptoms involve tremors, delirium, and convulsions. The mortality rate is about 25%.

Measures to reduce contact between the vesper mouse and humans may have contributed to limiting the number of outbreaks, with no cases identified between 1973 and 1994.

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