Florida's Invasive Burmese Pythons Carrying Three Newly Identified RNA Viruses, Study Finds

Florida's Burmese python problem has a new layer. A study published in the Journal of Virology found that the invasive snakes are carrying three previously unknown RNA viruses, and researchers are now trying to figure out whether any of them pose a risk to native wildlife.

The research started because of something else entirely: a 2020 disease outbreak in eastern mudsnakes, a species native to the Greater Everglades Ecosystem. In November and December of that year, some mudsnakes were found writhing on riverbanks with frothy oral discharge. Necropsies showed necrotising enteritis and pulmonary oedema. Scientists isolated a reptilian ferlavirus from the sick snakes.

Ferlaviruses are already known to cause serious, sometimes fatal illness in captive snakes. But this was the first documented outbreak in free-ranging snakes in the wild. Because the virus was genetically close to strains previously found in captive anacondas, researchers suspected an invasive constrictor in the Everglades might be part of the story.

So they went looking in the pythons. Researchers swabbed 40 Burmese pythons captured in and around the outbreak site. None of them carried the ferlavirus that sickened the mudsnakes. That theory came up empty.

Instead, the RNA sequencing turned up something nobody was looking for: three brand-new viruses never described before. An alphavirus named Eden alphavirus (EDEV), a hepacivirus called Burmese python hepacivirus (BuPyHV), and an arterivirus called Burmese python arterivirus. Researchers also found Burmese python septoviruses, a serpentovirus group already known from South Florida's pythons, so that one isn't new.

The numbers behind the three new viruses

Eden alphavirus turned up in 12 of the 40 pythons tested, or 30%, mostly from vent samples. Researchers could only recover a partial viral sequence, and attempts to grow the virus in lab cell cultures failed. Its closest known relative is Caainguá virus, first identified in mosquito pools in Brazil. According to the study, EDEV is the first new terrestrial alphavirus detected in the continental United States in more than 50 years. Whether it can actually cause disease is unknown, and the study found no evidence it infects humans.

Burmese python hepacivirus was the most common of the three, found in 26 of the 40 snakes tested, about 65%. Burmese python arterivirus was also newly described, though the available reporting does not specify its detection rate among the 40 snakes.

What this does and doesn't tell us

Finding a virus in an animal's blood or swabs doesn't mean that virus makes the animal sick, and it definitely doesn't mean it can jump to another species. The study authors themselves say further work is needed to determine whether any of these three viruses can infect native snakes.

Someone skeptical of alarm around this story has a fair point. New virus discoveries in wildlife happen constantly as genomic sequencing technology improves, and most of what gets found never amounts to a disease threat to anything beyond its original host. The failure to culture EDEV in lab cells, and the fact that only a partial sequence was recovered, suggests this isn't some neat, well-characterized pathogen ready to spread. Caution is warranted before anyone treats this as the next ecological crisis.

That said, the Everglades already has a well-documented invasive python problem that's done real damage to native mammal populations for years, independent of this virus question. Adding an unknown virus reservoir to that list has some significance, even if the practical risk turns out to be low.

The study doesn't say what happens next in terms of follow-up research, funding, or timeline. What it does establish is a baseline: Florida's pythons are hosts to at least three RNA viruses science didn't know existed until now, and whether those viruses matter for anything beyond the pythons themselves remains an open question.