A presentation at the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH) has announced that a deadly virus emerging in Bolivia can pass from human to human. Chapare virus, which causes hemorrhagic fever, had previously only been seen in small clusters of patients, but a recent outbreak saw several emergency service workers infected following exposure to a patient with the disease. At least three people were infected near Bolivia's capital city, La Paz, in 2019, two of whom died from the disease.
"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," said Caitlin Cossaboom, an epidemiologist with the Centers for Disease Control and Prevention (CDC), at the conference. "We now believe many bodily fluids can potentially carry the virus."
The discovery has called for all healthcare workers dealing with suspected cases of Chapare virus to take extreme care in order to avoid exposure from potential contaminants including blood, urine, saliva, and semen. The exact mechanism through which the illness passes from person to person is not yet known, but it’s suspected that saliva could play a role.
An ambulance medic who survived is thought to have caught Chapare from an infected medical resident who they resuscitated on route to the hospital. That same medical resident, who died from the disease, is thought to have contracted it after suctioning saliva from an infected patient. There was also evidence of viral RNA in a semen sample taken from a survivor 168 days after they were infected, indicating that sexual transmission is another way in which the virus could spread.
Chapare is an arenavirus, a group of pathogens that include the Lassa virus and Machupo virus, both of which caused deadly outbreaks in West Africa and Bolivia respectively. These arenaviruses cause hemorrhagic fever that results in patients suffering multiple organ complications and bleeding. This condition is also found in Ebola patients and is a complex one for health care teams to manage.
The source of the 2019 outbreak of Chapare in Bolivia has yet to be confirmed, but viral RNA was found in rodents close to the home of the first identified patient. Viral RNA on its own is not sufficient enough evidence to conclude rodents as the source but offers important insights that could help future investigations narrow down the cause. The rodents involved were pygmy rice rats and small-eared pygmy rice rats, both of which are found across Bolivia and some of its neighboring countries.
"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 ASTMH President Joel Breman, during the conference. "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."