Chapare hemorrhagic fever (CHHF) is a viral hemorrhagic fever caused by infection with Chapare virus. The Chapare virus is in the arenavirus family. Arenaviruses are usually spread to people through direct contact with infected rodents or indirectly through the urine or feces (droppings) of an infected rodent.

There have been two documented outbreaks of CHHF to date. The first occurred in 2003 in Chapare Province, Bolivia, which resulted in one fatal case. The second outbreak occurred in 2019 in Caranavi Province, Bolivia and resulted in five confirmed cases— three of which were fatal.

Though the rodent reservoir of Chapare virus is unknown, similar arenaviruses are typically transmitted to humans from infected rodents. Potential for initial infection depends on the habits of both humans and rodents. For example, infected rodents in field habitats are linked to infections in agricultural workers. If infected rodent species’ habitats include human homes or buildings, infection can also occur in domestic settings. There is also potential for laboratory or healthcare worker infections.

CHHF may also cause secondary person-to-person and nosocomial (healthcare setting) transmission. This may occur in a variety of ways. Person-to-person transmission is associated with direct contact with the blood or other body fluids (e.g saliva, urine, semen, respiratory secretions) of infected individuals. Contact with objects contaminated with these blood or body fluids, such as medical equipment, is also associated with transmission. In these situations, use of personal protective equipment (PPE) and disinfection procedures (together called barrier nursing) help prevent further spread of illness.

Geographically, the only documented outbreaks of CHHF to date have occurred in the Cochabamba and Caranavi regions of Bolivia. Related arenaviruses that have been documented to cause disease in humans have been found elsewhere in South America.

Though the rodent reservoir of Chapare virus is unknown, similar arenaviruses are typically transmitted either through direct or indirect contact with the saliva, urine, and droppings of infected rodents. Examples of direct contact include bites and scratches by infected rodents. Examples of indirect contact include breathing in the virus when it is stirred into the air or ingestion of food contaminated with the urine, salvia, or droppings of infected rodents.

An infected person can then spread the illness to other people through contact with the patient’s body fluids, or during procedures in healthcare settings that can aerosolize (spray particles of) the infected person’s body fluids—such as during chest compressions, CPR, and intubation. Because there are very few documented cases of Chapare in humans, more research is needed to understand how the virus spreads and causes illness.

The symptoms of CHHF resemble those of other South American hemorrhagic fevers, such as Argentine hemorrhagic fever (AHF) or Bolivian hemorrhagic fever (BHF).

Due to the low number of documented cases of CHHF, there is limited information about the progression of signs and symptoms of this illness and the incubation period. The incubation period, or the time between initial exposure to the development of symptoms, is variable and ranges from 4 – 21 days for arenaviruses.

The documented signs and symptoms of CHHF from the first and second outbreaks included some or all of the following:

• fever
• headache
• joint and muscle pain
• pain behind the eyes
• stomach pain
• vomiting
• diarrhea
• bleeding gums
• rash
• irritability

As is the case with other viral hemorrhagic fevers, these symptoms typically occur before later stage hemorrhagic signs (bleeding). The only described CHHF case in the first outbreak in 2003 died 14 days after symptoms began. The second outbreak occurred in 2019 and resulted in five confirmed cases, three of which were fatal (case fatality rate of 60%). Little is known about possible long-term complications or protective immunity following Chapare virus infection.

It is unknown if Chapare virus can be transmitted from mother to child; however, other arenaviruses have been documented to cause infection in utero. Evidence suggests that infection during pregnancy may cause complications, including miscarriage or death of the mother or neonate.

Because infection with Chapare virus infection can produce hemorrhagic symptoms in humans, often with a fatal outcome, work with suspected samples should be conducted using the highest biosecurity standards available (CDC advises a Biosafety Level 4 laboratory), strictly following all protocols for personal protection, sample inactivation and waste disposal. In the United States, Chapare virus is classified as a Select Agent.

CHHF virus was successfully isolated from both blood and serum during the acute febrile phase of illness in the first confirmed case in Bolivia in 2003. Subsequent complete genomic analysis of Chapare virus facilitated the development of specific molecular detection assays, including real-time reverse transcription polymerase chain reaction (rRT-PCR). Like other related arenaviruses, Chapare virus may be detectable in body fluids (serum, blood, semen, urine, respiratory secretions) of survivors following resolution of symptoms. These should be monitored prior to patient release.

Individuals from endemic areas and/or with compatible symptoms should be considered suspected cases and tested for Chapare virus using specific molecular detection assays that identify the virus. Depending on the region and clinical epidemiological picture of the patient, differential diagnoses may include Bolivian hemorrhagic fever (Machupo virus) or other South American New World arenaviruses, dengue, leptospirosis, yellow fever, hantavirus, and others. Serological assays specific for Chapare are not yet available.

There is currently no treatment for CHHF. Supportive therapy is important for recovery from and survival of CHHF. This includes:

• maintenance of hydration
• management of shock (eg, fluid resuscitation, administration of vasopressin stocks)
• sedation
• pain relief
• transfusions (when necessary)

Recovery

Because CHHF is rare and there have only been two described outbreaks, the precise mortality and risk factors for mortality are unknown. In the first known outbreak, the only confirmed case was fatal. In the second outbreak in 2019, three out of five documented cases were fatal (case-fatality rate of 60%).

Patients who recover from infections with arenaviruses may continue to shed virus in blood, saliva, urine, or semen for months after they no longer have symptoms. For this reason, these fluids should be monitored for the presence of Chapare virus, since recovering patients have the potential to infect others (particularly sexual partners or other household members) via these fluids. Little is known about possible long-term complications or protective immunity following Chapare virus infection.

Improving rodent control in and around homes and buildings can help to reduce exposure to rodents that may be infected with arenaviruses. Avoid contact with rodents, seal up holes and gaps in homes and other buildings surrounding the home to prevent or minimize rodent infestation or entry into the household. Place traps in and around homes to decrease rodent populations. Clean up any food that may be accessible to rodents.

People should avoid areas that are infested with rodents and other small mammals, or where they see signs of rodent infestation (droppings, etc.).

Chapare virus can be transmitted person-to-person. People who are sick with Chapare may be infectious in blood, saliva, urine, semen, respiratory secretions, and other body fluids while they have symptoms— and for months after they no longer have symptoms. Body fluids of sick and recovering people should be monitored for the presence of Chapare virus, since infected people have the potential to infect others (particularly household members, healthcare workers, and potentially sexual partners) via these fluids. For this reason, it is important to avoid contact with the body fluids of people who are sick with Chapare. Take precautions to avoid contact with body fluids (e.g. blood, saliva, urine, semen, respiratory secretions, etc) of infected people, even after they have recovered, until they have tested negative.

Precautions for preventing Chapare virus transmission in healthcare settings

Person-to-person transmission of Chapare virus has been documented as a result of close contact with infected patients, such as during aerosol-generating procedures in healthcare settings. Standard, contact and droplet precautions with eye protection should be implemented during management of suspected or confirmed CHHF cases in healthcare settings. Airborne precautions should be used when performing procedures that could generate infectious aerosols (such as endotracheal intubation, bronchoscopy or endoscopy, suctioning, chest, compressions, etc.).

Precautions when working with Chapare virus in laboratories

Infection with Chapare virus can produce hemorrhagic symptoms— often with a fatal outcome— in humans. Researchers studying the virus must only work with suspected samples using the highest biosecurity standards available (CDC recommends a biosafety level 4 laboratory), strictly following all protocols for personal protection, sample inactivation and waste disposal. In the United States, Chapare virus is classified as a Select Agent.