In the following lines, does Preston use ethos, pathos, or logos?

"What made [the life form] particularly interesting was that it multiplied easily in various species, in monkeys, humans, guinea pigs. It was extremely lethal in these species, which meant that its original host was probably not monkeys, humans, or guinea pigs but some other animal or insect that it did not kill. A virus does not generally kill its natural host." Page 139