Little-known deadly virus in Bolivia can spread from person to person, scientists discover

Researchers investigating a little-known deadly virus that causes a fever, vomiting and internal bleeding have found that it can be spread from person to person.

The recently-discovered Chapare virus, which claimed three lives during an outbreak in Bolivia last year, is thought usually to be spread to people through contact with infected rodents.

Researchers from the US Centers for Disease Control and Prevention (CDC) said confirmation of human-to-human transmission raised concerns about future outbreaks of the disease.

Chapare virus was first diagnosed in 2004 in Bolivia when a 22-year-old male farmer died after suffering from a headache, joint and muscle pain, vomiting and bleeding.

A second outbreak was reported in 2019 near Bolivia's capital city, La Paz – this time with five confirmed cases and three deaths.

Little is known about the virus apart from that it causes Ebola or Dengue Fever-like symptoms and has links to rodents and their droppings. There is currently no treatment, with patients given intravenous fluids and supportive care.

After the latest outbreak, teams from Bolivia's Ministry of Health, the CDC and the Pan-American Health Organisation (PAHO) were sent to investigate the origins of the disease and develop a diagnostic test.

Their findings, presented at the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH), show the virus can spread from person to person in healthcare settings.

Pigmy rice rats and small-eared pigmy rice rats, which are found across Bolivia in addition to several neighbouring countries, are thought to be one possible source of the virus.

But scientists admit there is still much that remains unknown about the Chapare virus, such as where it originated from, how exactly it infects humans, and what risks there are that a larger outbreak could occur in Bolivia or elsewhere in South America.

Caitlin Cossaboom, an epidemiologist with the CDC's division of high-consequence pathogens and pathology, said: “Our work confirmed that a young medical resident, an ambulance medic and a gastroenterologist all contracted the virus after encounters with infected patients – and two of these healthcare workers later died. We now believe many bodily fluids can potentially carry the virus."

Maria Morales-Betoulle, also at the CDC, said the team were quickly able to develop a RT-PCR test for detecting the virus – the same type of test often used to diagnose Covid-19.

She said: "We isolated the virus, and we were expecting to find a more common disease, but the sequence data pointed to Chapare virus.

"We were really surprised because the 2019 outbreak in La Paz occurred long after the first case was identified in 2004."

Since the study, the Bolivian Centre for Tropical Diseases has identified three additional suspected cases, including a child, although all are believed to have survived.

"While there is still much that remains unknown about Chapare virus, it's commendable how quickly this team was able to develop a diagnostic test, confirm human-to-human transmission and uncover preliminary evidence of the virus in rodents," said Joel Breman, president of the ASTMH.

"It's a valuable lesson that international scientific teams, equipped with the latest tools and freely sharing their insights, are our best front-line defense against the disruptive threats of deadly infectious diseases."