Recurring dengue outbreaks occur in cyclical pattern in most endemic countries. The recurrences of dengue virus (DENV) infection predispose the population to increased risk of contracting the severe forms of dengue. Understanding the DENV evolutionary mechanism underlying the recurring dengue outbreaks has important implications for epidemic prediction and disease control.
As a simian species, the langurs are not known to harbor simian retroviruses, except for one report on a simian Type D endogenous retrovirus from the spectacled langur (Trachypithecus obscurus) from Malaysia. The present report describes for the first time natural infection of the common Hanuman langur (Semnopithecus entellus) from India by a novel simian retrovirus (SRV). The new SRV is phylogenetically related to but distinct from the three molecularly characterized serotypes, SRV 1-3, of the five known serotypes of SRVs, based on sequence analyses from the 3'orf and env regions of the viral genome. The novel SRV isolated from the Indian Hanuman langur is provisionally named SRV-6.