Location of Bolivia
#18,574
While they tend to produce short-term, albeit sometimes deadly, outbreaks, numerous viral hemorrhagic fevers (VHFs) can be found around the globe. Most are carried by small mammals, and are caused by a variety of virus families, including Arenaviridae, Filoviridae, Flaviviridae, Hantaviridae, and Rhabdoviridae.
There is no cure for most VHFs; treatment is generally limited to supportive care. Fatality rates can range from less than 1% (Europe's Puumala Virus), to well over 50% (Ebola, Marburg).
While relatively rare, every year the U.S. reports between 10 and 50 Hantavirus Pulmonary Syndrome (HPS) cases, of which, roughly 35% prove fatal. Cases have been reported in 40 states (see map below), with > 90% of all cases reported west of the Mississippi River.
South America has their own array of VHF's, including several Hantaviruses (Andes virus (ANDV) is the most common), and a number of arenaviruses, including Argentine hemorrhagic fever, and the Machupo and Chapare viruses (see BMJ Global: Historical Trends Demonstrate a Pattern of Increasingly Frequent & Severe Zoonotic Spillover Events).
Most cases are caused by direct contact with an infected animal or their environment (animal dropping, urine, etc.). Some of these viruses have demonstrated limited human-to-human transmission, usually in a household or healthcare environment.
Yesterday the WHO announced a lab-confirmed case of Chapare virus in Bolivia. While the Chapare virus doesn't appear to present anywhere near the epidemic threat that Ebola, Marburg, or Nipah can, public health has only limited experience dealing with this pathogen.
I've reproduced excerpts from the WHO DON report below. Follow the link to read it in its entirety.
Chapare haemorrhagic fever- the Plurinational State of Bolivia
20 January 2025
Situation at a glance
On 7 January 2025, the International Health Regulations National Focal Point for the Plurinational State of Bolivia notified WHO of a laboratory-confirmed case of Chapare virus infection in an adult male from La Paz Department. Chapare haemorrhagic fever is an acute viral illness caused by Chapare virus. The virus was first identified in 2003 in Bolivia and has been associated with five documented outbreaks to date, all occurring within the country.These outbreaks have primarily affected rural areas in the La Paz Department, with the most recent case. There is no significant risk of international spread of the disease, as person-to-person transmission of the Chapare virus is possible but remains rare in the general population. As of 13 January 2025, no secondary cases have been reported, and all contacts remain without symptoms. Public health measures, such as disinfection and rodent control, have been implemented.
Description of the situation
On 7 January 2025, the International Health Regulations (IHR) National Focal Point (NFP) for the Plurinational State of Bolivia notified the World Health Organization (WHO) of one laboratory-confirmed human infection with Chapare virus (CHAPV) from one of the municipalities of La Paz Department. The patient is an adult male farmer in the age group of 50-60 years.
The patient developed symptoms including fever, headache, muscle pain, joint pain, and bleeding gums on 19 December 2024 and sought medical attention on 24 December. On 30 December, he was transferred to the local Health Center of the municipality due to worsening symptoms, where he died the same day. Blood samples were collected on 30 December before his death and sent to the National Center of Tropical Diseases (CENETROP), which confirmed CHAPV detection through real-time polymerase chain reaction (RT-PCR specific for CHAPV) testing on 2 January 2025.
An epidemiological investigation revealed significant risk factors for zoonotic disease transmission, including severe rodent infestation in and around the patient’s home. Environmental conditions such as wooden and corrugated metal housing, dirt floors, and peri-domestic coconut plantings created a conducive environment for rodent activity. The patient’s occupation as a farmer likely involved exposure to rodent burrows, further increasing the risk of infection.
Blood samples were collected from two close contacts of the case, which were negative. As of 13 January 2025, no secondary cases have been reported, and all identified contacts remain asymptomatic. Public health measures, including disinfection and rodent control, have been implemented, and investigations are ongoing. This is the fifth documented outbreak of Chapare haemorrhagic fever (CHHF) in Bolivia and globally since the virus was first identified in 2003.
Epidemiology
CHHF is a rare zoonotic disease caused by the CHAPV, a group of viruses belonging to the Mammarenavirus genus of the Arenaviridae family. These viruses are primarily transmitted to humans through infected rodents that serve as their natural hosts. Human transmission of Mammarenaviruses occurs mainly by inhalation of fine aerosol particles contaminated with virus-infected rodent excreta, such as urine, feces, or saliva.
Human-to-human transmission is uncommon but has been documented, particularly in healthcare settings where infection prevention and control (IPC) measures are inadequate. This mode of transmission occurs through contact with the blood or bodily fluids of infected individuals and can be amplified during aerosol-generating medical procedures.
The incubation period ranges from 4 to 21 days, after which individuals may develop symptoms including fever, headache, muscle aches, vomiting, diarrhea, and in severe cases, haemorrhagic manifestations. Due to the nonspecific nature of early symptoms, CHHF can be challenging to diagnose, often requiring laboratory confirmation through methods like real-time polymerase chain reaction.
Currently, there is no specific antiviral treatment for CHHF; management focuses on supportive care to alleviate symptoms and maintain vital organ function. Case fatality rates for CHAPV infections range from 15% to 30% in untreated patients, with rates as high as 67% reported during outbreaks. Preventive measures emphasize reducing human exposure to rodent populations and implementing stringent IPC practices in healthcare settings to mitigate the risk of transmission.
CHHF is currently known to only occur in Bolivia. In the last 20 years, four outbreaks have been documented in the country. The first was reported in 2003 in Chapare Province, Cochabamba Department, involving a single fatal case. In 2019, a second outbreak occurred in La Paz Department, resulting in nine cases, including four deaths (case fatality rate: 60%). This second outbreak was caused by a different CHAPV strain than the one identified in 2003. The third outbreak took place in 2021 in La Paz Department, with three confirmed cases (two fatal). The most recent outbreak occurred in 2024 with one laboratory-confirmed case, also within La Paz Department.
Public health response
The local and national health authorities implemented the following public health measures:Epidemiological investigation: A field investigation was conducted, during which rodent feces were detected. These feces did not belong to the known transmitter (Rattus rattus). The rodent infestation rate was calculated and found to be 75%.
Disinfection and rodent control: Disinfection measures and rodent control activities, including the use of rodenticides, were carried out both inside and outside the house.
Community surveillance: Health personnel, in collaboration with the municipal vector control program, conducted follow-up with families residing in the neighboring area of the case, due to the presence of rodents in these locations.
Community participation: Community engagement activities were carried out on 3 and 4 January 2025. These activities were planned by municipal and departmental health personnel to enhance awareness and participation in response efforts.
WHO risk assessment
One of the main challenges in detecting and responding to CHHF and other South American haemorrhagic fevers due to Mammarenavirus is the difficulty of making an early differential diagnosis due to the non-specificity of the initial clinical presentation. CHHF and other South American haemorrhagic fevers due to Mammarenavirus (e.g., Argentinian haemorrhagic fever, Bolivian haemorrhagic fever, and Sabia virus disease) should be considered for any patient presenting with suggestive symptoms originating from areas where Mammarenaviruses are known to circulate. These diseases should also be part of the differential diagnosis along with other endemic diseases such as malaria, dengue, yellow fever, and bacterial infections.
Environmental exposures, such as evidence of rodent activity in or around the home, contact with rodent excreta, or visiting or working in areas where rodents are prevalent, should be carefully considered as key epidemiological risk factors. Case ascertainment should involve asking about exposure to rodents or contact with patients suspected of having haemorrhagic fevers due to Mammarenavirus. For biosafety reasons, all samples from suspected cases in regions where CHHF has previously been reported should be managed as Mammarenavirus samples, even for differential diagnosis.
In Bolivia, the geographical at-risk area is limited to rural areas in the northern part of the La Paz department, particularly along a jungle corridor from Caranavi to Teoponte municipalities, passing through the town of Palos Blancos, where the reservoir is found. Currently, CHHF is reported only in Bolivia. There is no significant risk of international spread of the disease, as person-to-person transmission of the Chapare virus is possible but remains rare in the general population. Continued surveillance, public awareness, and adherence to infection prevention and control measures are critical to preventing further spread and mitigating future outbreaks.
