Florida’s Burmese pythons are carrying three previously unknown RNA viruses; scientists are investigating whether they could reach native snakes |
Burmese pythons in Florida’s Everglades are carrying three previously unknown RNA viruses, raising questions about whether viruses harboured by the invasive snakes could eventually affect native wildlife. A study published in the Journal of Virology examined 40 Burmese pythons captured in and around the site of a 2020 disease outbreak among eastern mudsnakes. Researchers did not find the ferlavirus linked to that outbreak in the pythons, but instead identified three previously undescribed viruses: an alphavirus, a hepacivirus and an arterivirus. They also detected a previously characterised serpentovirus. While the findings expand knowledge of viruses carried by invasive reptiles, researchers say further work is needed to determine whether any of these viruses can infect native snakes.
Florida’s Burmese pythons found carrying new RNA viruses
The research began after an outbreak among eastern mudsnakes in the Greater Everglades Ecosystem during November and December 2020. Some affected snakes were found writhing on riverbanks with frothy oral discharge, while examinations revealed necrotising enteritis and pulmonary oedema. Scientists isolated a reptilian ferlavirus from the sick mudsnakes. Ferlaviruses are known to cause serious and sometimes fatal disease in snakes kept in managed settings, but this was the first recognised outbreak in free-ranging snakes. Because the virus was genetically related to viruses previously found in captive anacondas, researchers investigated whether an invasive constrictor species in the Everglades might be involved in its ecology.
Researchers tested 40 Burmese pythons
Researchers collected oral and vent swabs from 40 Burmese pythons captured in and around the outbreak area. None tested positive for the ferlavirus found in the mudsnakes. Instead, RNA sequencing revealed three previously undescribed viruses: Eden alphavirus, Burmese python hepacivirus and Burmese python arterivirus. The researchers also detected Burmese python septoviruses, a group of serpentoviruses previously identified in South Florida’s Burmese pythons.
Eden alphavirus was found in nearly one-third of pythons
Eden alphavirus, or EDEV, belongs to the genus Alphavirus in the family Togaviridae. Researchers detected it in 12 of the 40 pythons, or 30%. Most detections came from vent samples. Only a partial viral sequence was recovered, and attempts to grow the virus in laboratory cell cultures were unsuccessful. EDEV’s closest known relatives include Caainguá virus, first identified in mosquito pools in Brazil. The researchers describe EDEV as the first new terrestrial alphavirus detected in the continental US in more than 50 years. However, its ability to cause disease remains unknown, and the study provides no evidence that it infects humans.
A new hepacivirus was found in most of the snakes
Burmese python hepacivirus, or BuPyHV, was the most frequently detected of the three newly identified viruses. It was found in 26 of the 40 pythons, meaning 65% had detectable viral RNA. The virus belongs to the genus Hepacivirus in the family Flaviviridae and is described by the researchers as the first hepacivirus identified in a snake. Although the genus also includes hepatitis C virus, BuPyHV is genetically distinct, and there is no evidence that it causes hepatitis in humans. Researchers identified an unusually elongated region in its genome and a possible additional protease-related protein whose function remains unknown.
The third virus was a previously unknown arterivirus
The third novel virus, provisionally named Burmese python arterivirus or BuPyAV, was detected in four of the 40 pythons, or 10%. It belongs to the family Arteriviridae. Researchers recovered only a short section of its genome, limiting what they could determine about its evolution. Its closest known relative was a greater green snake arterivirus identified in China. The study describes BuPyAV as the first reptilian arterivirus reported from North America. Its ability to cause disease or spread between animals has yet to be established.
More than half of the pythons carried multiple viruses
The researchers found that many of the pythons carried more than one virus. Two or three viruses were detected in 23 of the 40 animals, representing 57.5% of the sample. The most common combination was Burmese python hepacivirus and serpentovirus, detected together in nine pythons. Eden alphavirus and hepacivirus were found together in seven. The serpentoviruses identified in the study have previously been associated with respiratory disease in captive snakes. However, detecting viral RNA does not by itself establish that a particular snake was ill because of the virus.
Cross-species transmission remains an open question
The findings do not show that any of the three newly identified viruses have already spread from Burmese pythons to native snakes. Researchers instead identify cross-species transmission as an issue that warrants further investigation. The ferlavirus associated with the 2020 mudsnake outbreak was also absent from the 40 pythons tested, so the study does not establish that Burmese pythons caused or introduced that outbreak. The concern is largely ecological. Burmese pythons occupy the same environment as numerous native species, creating opportunities for pathogens to encounter new hosts. Scientists now need to determine whether the newly identified viruses can infect other snake species, replicate in them or cause disease.
Scientists need to determine what the viruses do
Finding viral genetic material is only the beginning. Researchers still need to establish how the viruses are transmitted, whether they can replicate in other species and whether they have any measurable effects on snake health or native ecosystems. The study’s viral sequences have been deposited in GenBank, providing material for further research. Published online on February 24, 2026, in the Journal of Virology, the study brings attention to the largely unexplored viral diversity associated with invasive Burmese pythons. For now, the evidence points to viral diversity rather than confirmed spread. The three viruses were detected in Burmese pythons, but their ability to move into native snake populations remains unknown.
