They are already the most endangered great apes. Now orangutans may face an additional threat: Ebola virus, or something a lot like it. “There could be filoviruses in nature that do not cause disease in primates,” notes Thomas Geisbert, an Ebola expert at UTMB. Antibodies to African Ebola might cross-react with those viruses, and give a positive test. But without an actual virus and its genetic sequence, says Geisbert, “I don't think you can say for sure that any virus associated with antibodies in these animals is the same as the African filoviruses.”