Commonly used viruses include adenoviruses, retroviruses, and various bacteriophages. Popular virus vectors are developed from retroviruses or adenoviruses. Viral causes include Coxsackie virus, mumps and adenoviruses. Adenoviruses can also cause viral meningitis or encephalitis. With adeno-associated viruses and adenoviruses, the genomes remain episomal. Many other viruses, including caliciviruses, herpesviruses, adenoviruses and parvoviruses, circulate in marine mammal populations. Dependoparvoviruses, previously known as dependoviruses, require helper viruses (e.g. adenoviruses or herpesviruses) to replicate. Adenoviruses represent the largest known nonenveloped viruses. Viral genomes are circular, as in the polyomaviruses, or linear, as in the adenoviruses. Some adenoviruses under specialized conditions can transform cells using their early gene products. Adenoviruses are being actively developed as vaccines. Adenoviruses, types 40 and 41 can also cause gastroenteritis. Bat adenoviruses are closely related to those finds in canids. Diseases, such as HIV and human adenoviruses have been associated with NHP interactions. Chlorhexidine is ineffective against polioviruses and adenoviruses.