Paramyxoviruses in the genus Ferlavirus were first described in snakes in the 1970’s. These viruses are most often found in snakes, but infection of lizards and chelonians have also been described. Ferlaviruses are mostly respiratory pathogens, but systemic and CNS disease can also occur. Four ferlavirus genogroups can be differentiated: A, B, C, and “tortoise”. Natural infection is believed to occur through aerosol or smear infection and spread through airways in large collections has been documented. Disease development appears to depend on multiple factors, including virus strain, host species, and the environment. Studies in corn snakes (Pantherophis guttatus) and ball pythons (Python regius) indicate that immune response to infection, degree of inflammation, and secondary bacterial infections likely play an important role in disease outcomes. Diagnosis of ferlaviral infections can be based either on virus detection, most often through PCR, or detection of antibodies against ferlaviruses, most often through hemagglutination inhibition assay (HI). However, there are a number of challenges when using either method, including the genetic and serological differences between strains. The existence of long-term carriers and the ability of these viruses to cause severe disease outbreaks in collections makes them particularly important for any quarantine examination.