Scientists are urging caution over a mysterious, Ebola-like viral disease that appears to have spread from person to person during a small outbreak in Bolivia last year. The disease, caused by the Chapare virus, killed three people and is thought to have sickened at least five during the outbreak, including three healthcare workers who came into contact with patients. Its symptoms include internal bleeding, fever, and widespread organ damage.
The virus is named after the location where the first known outbreak of the disease occurred in late 2003, near the Chapare River in Bolivia. Though several people were suspected of having the disease in 2003 and 2004, detailed information and blood samples were only collected from a single patient at the time: a 22-year-old tailor and farmer living in the rural village of Samuzabeti.
The man initially developed headache and fever, which progressed to joint aches, vomiting, and internal bleeding, also called hemorrhaging. This collection of symptoms is known as hemorrhagic fever and is a familiar, often fatal outcome of other very dangerous but usually rare viral diseases like Ebola. Within two weeks, the man died.
Doctors were able to study his blood and isolate a virus never before documented, while ruling out other potential illnesses common to the area like dengue. The mystery virus was discovered to be a member of the arenavirus family, a group of viruses that commonly infect rodents and sometimes humans. Its relatives include the more well-known Lassa virus and other viruses first found in South America, such as Machupo virus in Bolivia and Junin virus in Argentina. Many of these viruses can cause hemorrhagic fever in people.
In 2019, the Chapare virus made a reappearance in Bolivia, first being found in a farm worker who developed hemorrhagic fever and ultimately died as a result. After it became apparent the patient’s alarming symptoms weren’t caused by dengue or more mundane illnesses, health officials began a detailed investigation, eventually enlisting the help of the Centers for Disease Control and Prevention in the U.S. CDC experts then confirmed that the worker had come down with the Chapare virus.
Most arenaviruses that make people sick are known to spread from rodents to people. Usually, this happens when people breathe in aerosols from dried-out rodent urine or droppings contaminated with the virus or otherwise come into direct contact with rodents. During this latest outbreak, health officials did find viral traces of Chapare in rodents near where the farmer worked, according to research presented this week at the virtual annual meeting of the American Society of Tropical Medicine and Hygiene.
But at least three health care workers who interacted with infected patients—a medical resident, an ambulance worker, and a gastroenterologist—also developed illness, with two eventually dying. Health officials strongly believe the virus was spread from person to person in these other cases. Another concerning finding was that viral traces could be found in the semen of a survivor more than 160 days after infection, something that’s also been documented for hemorrhagic fever viruses like Ebola.
“We now believe many bodily fluids can potentially carry the virus,” said Caitlin Cossaboom, an epidemiologist with the CDC’s Division of High-Consequence Pathogens and Pathology, in a statement released by the American Society of Tropical Medicine and Hygiene.
Given the ongoing pandemic and how it began, it’s understandable to be worried by this news. But while that’s not totally unwarranted, it should be noted that most human outbreaks of arenaviruses tend to be limited, as this one was. And their main route of transmission is still predominantly from rodents to people. Even if this virus can spread from person to person, it appears to be through direct contact with bodily fluids like blood or saliva, which limits its potential for spread, as does its lethality. Contrast that with something like covid-19, which is a respiratory illness that easily spreads through the respiratory system—simply breathing the same air as an infected person—and can be transmitted even before someone is visibly sick.
That said, it’s definitely important for epidemiologists and other scientists to keep a close eye on potential threats like Chapare virus, especially in areas of the world where health care resources are limited, increasing the potential risk of transmission to health care workers. Even viruses that only really spread through direct contact with bodily fluids can erupt into large outbreaks under the right conditions, such as when an outbreak of Ebola in West Africa in 2014 nearly infected 30,000 people and killed over 11,000. The Lassa virus, related to Chapare, also regularly infects as many as 300,000 people a year in the areas of Africa where it’s found, killing an estimated 5,000 annually.
For now, scientists plan to learn as much as they can about the Chapare virus from these latest cases, including its likely rodent hosts, where it may have originated, and whether it’s been circulating in the country unbeknownst to doctors. Following the 2019 outbreak, doctors have since documented three other possible cases, though all the patients survived.