Iquitos virus: a novel reassortant Orthobunyavirus associated with human illness in Peru

Abstract

Oropouche (ORO) virus, a member of the Simbu serogroup, is one of the few human pathogens in the Orthobunyavirus genus in the family Bunyaviridae. Genetic analyses of ORO-like strains from Iquitos, Peru, identified a novel reassortant containing the S and L segments of ORO virus and the M segment of a novel Simbu serogroup virus. This new pathogen, which we named Iquitos (IQT) virus, was first isolated during 1999 from a febrile patient in Iquitos, an Amazonian city in Peru. Subsequently, the virus was identified as the cause of outbreaks of "Oropouche fever" during 2005 and 2006 in Iquitos. In addition to the identification of 17 isolates of IQT virus between 1999 and 2006, surveys for neutralizing antibody among Iquitos residents revealed prevalence rates of 14.9% for ORO virus and 15.4% for IQT virus. Limited studies indicate that prior infection with ORO virus does not seem to protect against disease caused with the IQT virus infection. Identification of a new Orthobunyavirus human pathogen in the Amazon region of Peru highlights the need for strengthening surveillance activities and laboratory capabilities, and investigating the emergence of new pathogens in tropical regions of South America.

Figure 1. Neighbor joining phylogenetic tree of the Oropouche virus based on the S segment.

The tree was derived from recently generated partial nucleoprotein gene sequences of recent ORO-like virus isolates from Peru (depicted in red or italics) and previously published homologous sequences, using the neighbor joining program. Virus strains are labeled by code designation. The tree was rooted using an outgroup comprised of Sathuperi virus. Numbers indicate bootstrap values for the clades to the right.

Figure 2. Neighbor-joining phylogenetic tree of the M segment RNA of members of the Simbu serogroup.

The tree was constructed based on partial sequences of the Gc gene. Bootstrap values were obtained based on 500 replicates. Virus abbreviations are as follows: Kai, Kaikalur; Shu, Shuni; Dou, Douglas; Sat, Sathuperi; Sim, Simbu; San, Sango; Sha, Shamonda; But, Buttonwillow; Uti, Utinga; Ing, Ingwavuma; Mer, Mermet; Man, Manzanilla; FP, Facey's Paddock; Thi, Thimiri; Jat, Jatobal; ORO, Oropouche.

Figure 3. ORO and IQT9924 antibody prevalence among residents from different neighborhoods in Iquitos.

ORO virus antibody prevalence is shown in black, underlined numbers represent IQT9924 virus antibody prevalence.