Since the discovery of the human partetravirus, related animal viruses have been found in various mammalian species. We first reported the discovery of porcine and bovine partetraviruses (also known as hokoviruses previously), which are novel related animal parvoviruses found in Hong Kong [19] . Closely related porcine partetraviruses have since been found in German wild boar populations [20] , while human partetravirus-like viral DNA was detected in the plasma samples of a chimpanzee and baboon in Cameroon [21] . As the genetic distances between human partetravirus and other known parvoviruses at the time of its discovery were relatively large, it was unclear if the human partetravirus had diverged from a human parvovirus ancestor early in the history of parvovirus evolution or if it had diverged from an undiscovered animal parvovirus. Parvovirus evolution is characterized by the development of host-specificity and congruent viral and host phylogenies [22] , which has led to the hypothesis of long-term co-evolution of parvoviruses and their hosts. In addition, evolutionary rates can vary significantly among different parvovirus species [23, 24] , which complicates evolutionary analysis between distant parvoviruses. Hence, the identification of related partetraviruses in animals has contributed to our knowledge of the evolutionary history of the human partetravirus.