"Sharks are remarkably resistant to viruses," study researcher Michael Zasloff, of the Georgetown University Medical Center, told LiveScience. Zasloff discovered the molecule, squalamine, in 1993 in the dogfish shark, a small- to medium-size shark found in the Atlantic, Pacific, and Indian Oceans.

"It looked like no other compound that had been described in any animal or plant before. It was something completely unique," Zasloff said. The compound is a potent antibacterial and has shown efficacy in treating human cancers and an eye condition known as macular degeneration, which causes blindness.

Zasloff's new research shows it can also kill many human liver viruses, though a few researchers who weren't involved in the study do have concerns that in order to see an effect, you'd need toxic levels of the molecule.

The researchers decided to test the compound on several different live viruses that infect liver cells, including hepatitis B, dengue virus and yellow fever. They saw high efficacy across the board.

The researchers were unable to test the compound against hepatitis C, a virus that infects the livers of about 1.5 percent of the U.S. population and can cause liver cancer, because hepatitis C doesn't grow well in lab models like rats. Yellow fever virus is often used as a surrogate lab test to show possible efficacy against hepatitis C, and the researchers were able to cure yellow fever in hamsters with squalamine.