Novel Strain of Andes Virus Associated with Fatal Human Infection, Central Bolivia

Cristhopher D. Cruz, Brett M. Forshey

, Efrain Vallejo, Roberto Agudo, Jorge Vargas, David L. Blazes, Carolina Guevara, V. Alberto Laguna-Torres, Eric S. Halsey, and Tadeusz J. Kochel

Author affiliations: US Naval Medical Research Unit 6, Lima, Peru (C.D. Cruz, B.M. Forshey, D.L. Blazes, C. Guevara, V.A. Laguna-Torres, E.S. Halsey); Servicio Departamental de Salud, Cochabamba, Bolivia (E. Vallejo, R. Agudo); Centro Nacional de Enfermedades Tropicales, Santa Cruz, Bolivia (J. Vargas); US Naval Medical Research Center, Silver Spring, Maryland, USA (T.J. Kochel)

Abstract

To better describe the genetic diversity of hantaviruses associated with human illness in South America, we screened blood samples from febrile patients in Chapare Province in central Bolivia during 2008–2009 for recent hantavirus infection. Hantavirus RNA was detected in 3 patients, including 1 who died. Partial RNA sequences of small and medium segments from the 3 patients were most closely related to Andes virus lineages but distinct (<90% nt identity) from reported strains. A survey for IgG against hantaviruses among residents of Chapare Province indicated that 12.2% of the population had past exposure to >1 hantaviruses; the highest prevalence was among agricultural workers. Because of the high level of human exposure to hantavirus strains and the severity of resulting disease, additional studies are warranted to determine the reservoirs, ecologic range, and public health effect of this novel strain of hantavirus.

Hantaviruses (family Bunyaviridae, genus Hantavirus) are trisegmented negative-strand RNA viruses in which the small (S), medium (M), and large (L) genomic segments encode for the nucleocapsid protein (N), 2 envelope glycoproteins (Gn and Gc), and the viral polymerase, respectively. Hantaviruses are maintained in rodent reservoirs, and human exposure typically results from inhalation of aerosols from infectious urine or feces, although human-to-human transmission of Andes virus (ANDV) has also been described (1). Human hantavirus infection in South America is often associated with rapid onset of severe disease manifestations, such as respiratory failure and cardiac dysfunction referred to as hantavirus pulmonary syndrome (HPS) and case-fatality rates >50% (2,3). Despite the public health effects, in most cases of human infection, the precise etiologic agent is not identified. Thus, the extent of genetic diversity and geographic distribution of distinct hantavirus strains is not well understood.
Since the first identification of HPS in 1993, many new hantaviruses have been described throughout North, Central, and South America. Studies of rodent reservoirs in South America have identified an increasingly complex picture of hantavirus diversity and ecology (2,4). Unique strains of hantavirus have been identified in rodents in Venezuela (5,6), Peru (7), Brazil (8–10), Argentina (11–13), Paraguay (14,15), and Chile (11,16), many of which have also been associated with human illness. In Bolivia, the first hantavirus identified was Río Mamoré virus (RIOMV), which was isolated from a pygmy rice rat (Oligoryzomys microtis) (17) but has not been associated with human disease. In 1997, a Laguna Negra virus (LNV) variant was identified in an HPS patient in Chile who had traveled extensively in Bolivia (18,19). An ecologic assessment of reservoir hosts identified the large vesper mouse (Calomys callosus) as reservoir host of LNV in Bolivia (20). The association of ANDV (Nort lineage) and Bermejo virus (BMJV) with 2 HPS cases in southern Bolivia in 2000 documented the first human infection by BMJV (21).
To further describe the diversity of hantavirus strains associated with human disease in Bolivia, we screened febrile patients reporting to 2 health centers in Chapare Province for serologic and molecular evidence of hantavirus infection. We describe the clinical signs and symptoms and genetic characterization (partial S and M segment) of a novel strain of hantavirus in 3 patients, including 1 who died. In addition, we report results of a survey to determine the prevalence of previous hantavirus exposure in the region.