Marco, Timbó and Chaco are three newly recognized arboviruses isolated from pools of heart and liver of lizards captured near Belém, Pará, Brazil. Four strains of Marco virus, six of Timbó and three of Chaco were detected in Ameiva ameiva ameiva. A fourth strain of Chaco virus was isolated from Kentropyx calcaratus.
No serological relationship of Marco virus to other arboviruses has so far been demonstrated. Timbó and Chaco cross-react in complement-fixation testing but have not been shown to be related to any other arbovirus.
These viruses have not been recovered from birds, amphibians, rodents, marsupials, primates, bats, edentates, carnivores, horses, cattle or arthropods in the Amazon region, and it is proposed that the lizard is their principal vertebrate host.