Hantavirus (Bunyaviridae) infections in rodents from Orange and San Diego counties, California.

During a screening program to determine the extent of hantavirus activity in Orange and San Diego Counties, California, serum samples from 2,365 rodents representing nine genera and 15 species were tested for hantavirus antibodies. A reverse transcription-polymerase chain reaction on selected seropositive rodents was used to identify the specific hantavirus. Rodents positive for Sin Nombre virus (SNV) antibodies by Western blot included 86 (9.1%) of 948 deer mice (Peromyscus maniculatus), four (1.5%) of 275 California mice (Peromyscus californicus), one (0.5%) of 196 cactus mice (Peromyscus eremicus), 51 (12.2%) of 417 harvest mice (Reithrodontomys megalotis), and five (12.5%) of 40 California voles (Microtus californicus). All other specimens tested were negative for hantavirus antibodies. There was a correlation between age and sex of the reservoir host and prevalence of SNV antibody, especially among male deer mice and harvest mice. Few seasonal trends in antibody prevalence were observed and continued maintenance of SNV and El Moro Canyon virus was found at several foci over a 4-5-year period. Isla Vista virus was also found in voles and represents the first recorded in Orange County. Microhabitat selection on the part of these rodents based on plant density, plant height, and availability of food plants may explain, to some extent, all of the hantavirus-positive foci throughout the study area over a broad geographic range and the lack of antibody-positive rodents in dense chaparral, woodland, and riparian areas. The majority of rodents positive for SNV was identified from localities along coastal bluffs and the foothills of the Santa Ana Mountains, where trap success was high and P. maniculatus represented 43% of all rodents collected. Several residential, commercial, and industrial sites exist in these areas and the potential health risk should not be overlooked. This study represents an in-depth analysis of the prevalence, host distribution, and characteristics of rodent populations infected by three hantaviruses within a small, well-defined, geographic area.

High prevalence of hantavirus infection in Indian communities of the Paraguayan and Argentinean Gran Chaco.

Serologic evidence of past infection with a Sin Nombre-like hantavirus(es) was demonstrated in 78 (40.4%) of 193 Indians living in western Paraguay and in 38 (17.1%) of 222 Indians inhabiting the Salta province of northern Argentina. In both populations seroprevalence increased with age, with the most striking increase occurring at 18 years of age in the Paraguayan population and at 35 years of age in the Salta population. The peak prevalences in both populations (66.6% and 44.0%, respectively) were seen in Indians > 53 years old. Although no sex difference was observed in the Paraguayan Indians, in the Salta population seroprevalence was greater in males than in females. Familiar clustering of the infection was observed. The data indicate that the Indian populations of the Gran Chaco are frequently exposed to and survive infection with a Sin Nombre-like virus(es). Possible explanations of this novel epidemiology are discussed.

Serologic survey for hantavirus infection in domestic animals and coyotes from New Mexico and northeastern Arizona.

OBJECTIVE: To determine whether animals had serologic evidence of infection with Sin Nombre virus (SNV). DESIGN: Prospective serosurvey. SAMPLE POPULATION: Serum samples were obtained from 145 cats, 85 dogs, 120 horses, and 24 cattle between April 1993 and August 1994 and 54 coyotes between December 1994 and February 1995. PROCEDURE: Serum samples were analyzed by western immunoblot assays for reaction with SNV nucleocapsid antigen. Samples with reactivity to SNV nucleocapsid proteins were used to probe multiple-antigen blots containing recombinant fusion proteins derived from prototypic hantaviruses. Lung tissue or blood clots were used in nested reverse-transcriptase polymerase chain reaction assays for a 320-nucleotide portion of the SNV G1 gene. RESULTS: Sera from 4 of 145 (2.8%) cats and 4 of 85 (3.5%) dogs had trace reactivity to full-length SNV-encoded nucleocapsid proteins. All samples from horses, cattle, and coyotes were nonreactive. Sera from cats and dogs that had trace IgG-antibody reactivity to nucleocapsid proteins were then tested for IgG-antibody reactivity to nucleocapsid proteins of prototypic hantaviruses. One cat had multiple cross-reactivities with these hantaviruses, consistent with exposure to a hantavirus; however, epitope mapping studies did not support this conclusion. Reverse-transcriptase polymerase chain reaction studies of blood clots or lung tissue from 2 animals that had weak reactivity to SNV failed to amplify any hantavirus sequence. CLINICAL IMPLICATIONS: Domestic animals, particularly dogs and cats, as well as coyotes do not appear to have a major role in the maintenance and transmission of SNV.

Bayou virus-associated hantavirus pulmonary syndrome in Eastern Texas: identification of the rice rat, Oryzomys palustris, as reservoir host.

We describe the third known case of hantavirus pulmonary syndrome (HPS) due to Bayou virus, from Jefferson County, Texas. By using molecular epidemiologic methods, we show that rice rats (Oryzomys palustris) are frequently infected with Bayou virus and that viral RNA sequences from HPS patients are similar to those from nearby rice rats. Bayou virus is associated with O. palustris; this rodent appears to be its predominant reservoir host.

Rio Mamore virus: genetic characterization of a newly recognized hantavirus of the pygmy rice rat, Oligoryzomys microtis, from Bolivia.

Human hantavirus disease occurs throughout much of South America. The rodent hosts and the specific etiologic agent(s) are largely unknown, but many reported cases occurred within the habitation ranges of oryzomine rodents (rice rats). We have identified a genetically novel hantavirus (Rio Mamore virus [RM]) of the pygmy rice rat Oligoryzomys microtis in Bolivia. The complete sequence of the small (S) genome and the partial sequence of the medium (M) genome are described. This virus is closely related to the newly identified human pathogen Andes virus from Patagonia. To facilitate improved diagnosis of hantavirus infections in South America, we have expressed the complete nucleocapsid protein of RM in Escherichia coli and affinity-purified it for use in an ELISA and Western blot assays for antibodies to RM.

Rapid and specific detection of Sin Nombre virus antibodies in patients with hantavirus pulmonary syndrome by a strip immunoblot assay suitable for field diagnosis.

To develop a rapid antibody test for Sin Nombre hantavirus (SNV) infection for diagnosis of hantavirus pulmonary syndrome (HPS) in field settings where advanced instrumentation is not available, a strip immunoblot assay bearing four immobilized antigens for SNV and a recombinant nucleocapsid protein antigen of Seoul hantavirus (SEOV) was prepared. The SNV antigens included a full-length recombinant-expressed nucleocapsid (N) protein (rN), a recombinant-expressed G1 protein (residues 35 to 117), and synthetic peptides derived from N (residues 17 to 59) and G1 (residues 55 to 88). On the basis of the observed reactivities of hantavirus-infected patient and control sera, we determined that a positive assay requires reactivity with SNV or SEOV rN antigen and at least one other antigen. Isolated reactivity to either viral rN antigen is indeterminate, and any pattern of reactivity that does not include reactivity to an rN antigen is considered indeterminate but is unlikely to represent hantavirus infection. Fifty-eight of 59 samples from patients with acute SNV-associated HPS were positive according to these criteria, and one was initially indeterminate. Four of four samples from patients with HPS due to other hantaviruses were positive, as were most samples from patients with SEOV and Puumala virus infections. Of 192 control serum samples, 2 (1%) were positive and 2 were indeterminate. Acute SNV infection was distinguishable from remote SNV infection or infection with hantaviruses other than SNV by the presence of G1 peptide antigen reactivities in the former. The strip immunoblot assay shows promise for the detection of SNV antibodies early in the course of HPS.

Cocirculation of multiple hantaviruses in Texas, with characterization of the small (S) genome of a previously undescribed virus of cotton rats (Sigmodon hispidus).

An environmental and laboratory investigation was conducted after a fatal childhood case of hantavirus pulmonary syndrome occurred in Deaf Smith County, Texas in May 1995. A trapping campaign was conducted to identify possible rodent carriers. Six species of murid and heteromyid rodents were collected, and at least one hantavirus-seropositive specimen was found in each of the five murid species. Tissues from a selection of 11 seropositive specimens were examined by the polymerase chain reaction (PCR) and sequencing of viral genetic material. The predominant hantavirus was El Moro Canyon virus (ELMCV), which occurred in three of three harvest mice (Reithrodontomys megalotis) and in three of four deer mice (Peromyscus maniculatus) examined. Sin Nombre virus (SNV) was found in one deer mouse and one white-footed mouse (P. leucopus). A seropositive house mouse (Mus musculus) was negative by PCR. Two cotton rats (Sigmodon hispidus) were infected by a virus of novel genotype (Muleshoe virus [MULEV]) that bears closet resemblance to Bayou hantavirus. The sequence of the complete small genomic segment was determined for one MULEV, and high-level expression of its nucleocapsid protein was induced in Escherichia coli. Serologic studies indicated that the most likely etiologic agent in the human infection was SNV.

Hantavirus pulmonary syndrome, renal insufficiency, and myositis associated with infection by Bayou hantavirus.

Hantaviruses are etiologic agents of hemorrhagic fever with renal syndrome, an acute illness characterized by acute renal insufficiency, proteinuria, and hemodynamic instability. Recently, a New World form of hantavirus disease, hantavirus pulmonary syndrome (HPS), was recognized; in this form, pulmonary edema is prominent, but renal insufficiency is generally lacking. HPS cases from the southeastern United States may be exceptional in that they have exhibited both pulmonary and renal manifestations. One case in Louisiana and one case in Florida were linked to infection by the distinct but closely related Bayou and Black Creek Canal hantaviruses, respectively. We report a nonfatal case of HPS caused by Bayou hantavirus that occurred in eastern Texas. Clinical manifestations included pulmonary and renal insufficiency and myositis, which had previously been observed in the patient from Florida. The occurrence of distinctive clinical abnormalities in HPS cases from the southeastern United States supports the concept that there are clinically significant differences between western and southeastern forms of HPS.

Epidemiologic linkage of rodent and human hantavirus genomic sequences in case investigations of hantavirus pulmonary syndrome.

Sin Nombre virus (SNV) causes the zoonotic disease hantavirus pulmonary syndrome (HPS). Its mechanisms of transmission from rodent to human are poorly understood. It is possible that specific genetic signature sequences could be used to determine the probable site of each case-patient's exposure. Environmental assessments suggested 12 possible sites of rodent exposure for 6 HPS patients. Rodents were captured at 11 of the 12 sites and screened for SNV infection within 2 weeks of the patient's diagnosis. Viral sequences amplified from tissues of rodents at each site were compared with those from case-patients' tissues. Rodents bearing viruses with genetic sequence identity to case-patients' viruses across 2 genomic segments were identified in 4 investigations but never at >1 site. Indoor exposures to rodents were especially common at implicated sites. By distinguishing among multiple possible sites of exposure, viral genotyping studies can enhance understanding of the conditions associated with infection by SNV.

Isla Vista virus: a genetically novel hantavirus of the California vole Microtus californicus.

Prospect Hill virus (PH) was isolated from a meadow vole (Microtus pennsylvanicus) in 1982, and much of its genome has been sequenced. Hantaviruses of other New World microtine rodents have not been genetically characterized. We show that another Microtus species (the California vole M. californicus) from the United States is host to a genetically distinct PH-like hantavirus, Isla Vista virus (ILV). The nucleocapsid protein of ILV differs from that of PH by 11.1% and a portion of the G2 glycoprotein differs from that of PH by 19.6%. ILV antibodies were identified in five of 33 specimens of M. californicus collected in 1975 and 1994-1995. Enzymatic amplification studies showed that 1975 and 1994-1995 ILV genomes were highly similar. Secondary infection of Peromyscus californicus was identified in Santa Barbara County, California. A long-standing enzootic of a genetically distinct hantavirus lineage is present in California voles.

Molecular linkage of hantavirus pulmonary syndrome to the white-footed mouse, Peromyscus leucopus: genetic characterization of the M genome of New York virus.

The complete M segment sequences of hantaviruses amplified from tissues of a patient with hantavirus pulmonary syndrome in the northeastern United States and from white-footed mice, Peromyscus leucopus, from New York were 99% identical and differed from those of Four Corners virus by 23%. The serum of this patient failed to recognize a conserved, immunodominant epitope of the Four Corners virus G1 glycoprotein. Collectively, these findings indicate that P. leucopus harbors a genetically and antigenically distinct hantavirus that causes hantavirus pulmonary syndrome.

Nucleotide sequence analysis of the M genomic segment of El Moro Canyon hantavirus: antigenic distinction from four corners hantavirus.

El Moro Canyon hantavirus (ELMC, previously known as HMV-1) is associated with the western harvest mouse Reithrodontomys megalotis. The interpretation that ELMC is a novel hantavirus was based upon comparisons of the nucleotide sequence of the S genomic segment with those of other hantaviruses. We now show that the ELMC M genome, like the S genome, is genetically similar to but distinct from that of Four Corners hantavirus (FC). The ELMC M genome is 3801 nt in length and encodes a glycoprotein precursor of 1139 amino acids. The G1 and G2 genes are 71 and 73.1% identical to those of FC and the corresponding glycoproteins are 73.5 and 82.3% identical. A portion of the G1 glycoprotein of ELMC that is homologous to an important linear epitope of FC differs from the FC epitope by 10 of 31 residues. That domain and flanking sequences were expressed in Escherichia coli. G1 antibodies from 3 of 19 FC-infected patients showed cross-reactivity with ELMC by Western blot assay. The portion of the ELMC G1 antigen recognized by those antibodies is the region of homology to the FC epitope. These data support our previous interpretation that ELMC is distinct from FC and other hantaviruses.

Phylogenetically distinct hantavirus implicated in a case of hantavirus pulmonary syndrome in the northeastern United States.

Hantavirus pulmonary syndrome (HPS) is an acute respiratory illness with high mortality. It is caused by a newly described New World hantavirus known as Four Corners virus (FCV). Nearly all cases of HPS have occurred in the western United States. The etiologic agents in those cases have been closely related to each other, based upon comparisons of their genetic sequences. We have molecularly cloned the S genomic segment of a hantavirus (Rl-1) implicated in a case on HPS in the northeastern United States. Nucleotide sequence analysis shows that the Rl-1 virus has many similarities to FCV, but is clearly distinct from the western forms of that virus. These data suggest that HPS can be caused by multiple agents that together form a distinctive evolutionary clade.

Prevalence and geographic genetic variation of hantaviruses of New World harvest mice (Reithrodontomys): identification of a divergent genotype from a Costa Rican Reithrodontomys mexicanus.

We recently described a novel hantavirus (HMV-1) of the western harvest mouse Reithrodontomys megalotis. Screening of 181 additional specimens of Reithrodontomys from the United States and Mexico, including samples of R. mexicanus, R. sumichrasti, and R. gracilis of Costa Rica, for antibodies to hantavirus nucleocapsid protein revealed a widespread enzootic of hantavirus infection. Genetic analyses of 7 S genomes of Reithrodontomys-associated hantaviruses demonstrated that the enzootic of HMV-1 extends from central Mexico into the southwestern United States. A presumed deer mouse hantavirus was found in an R. megalotis animal in Mexico. A highly divergent HMV-1-like virus, tentatively called HMV-2, was identified in a Costa Rican R. mexicanus. These data suggest a longstanding radiation of hantaviruses among New World harvest mice. We identify possible opportunities for genetic exchange among hantaviruses of related rodent hosts.

Dominant glycoprotein epitope of four corners hantavirus is conserved across a wide geographical area.

A newly identified hantavirus, tentatively called Four Corners virus (FCV), was found to be the aetiological agent of a 1993 outbreak of hantavirus pulmonary syndrome (HPS) in the southwestern United States. Immunodominant epitopes of 43 and 31 amino acids were identified in the nucleocapsid protein and G1 glycoprotein, respectively. The G1 genes of different hantaviruses are highly divergent, suggesting that geographically diverse FCVs might fail to cross-react owing to antigenic drift. We now show that the immunodominant epitope of G1 is conserved among 18 FCVs from a broad geographical area, despite extensive nucleotide sequence heterogeneity. Antibodies from all 45 HPS patients, separated by more than 3000 km were shown to be reactive with the dominant G1 epitope. Evidence for limited cross-reactivity between the G1 antigen of a novel hantavirus of the cotton rat and that of FCV is presented.

Genetic identification of a novel hantavirus of the harvest mouse Reithrodontomys megalotis.

We have cloned the S genomic segment of a novel hantavirus of the harvest mouse Reithrodontomys megalotis. The virus is phylogenetically distinct from other hantaviruses. The new hantavirus was identified in harvest mice separated by approximately 1,000 km. A wood rat (Neotoma mexicana) was found to be infected with the harvest mouse hantavirus.

Detection of Muerto Canyon virus RNA in peripheral blood mononuclear cells from patients with hantavirus pulmonary syndrome.

To determine if Muerto Canyon Virus (MCV) RNA is present in the peripheral blood of patients with hantavirus pulmonary syndrome, a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for MCV RNA was used on blood samples from 20 seropositive case-patients. RNA was prepared from peripheral blood mononuclear cells (PBMC) or blood clot (or both) from 19 and from plasma from 11 case-patients. All 12 blood clot, all 13 PBMC, and 8 of 11 plasma preparations produced an MCV amplification product after RT-PCR with primers from the G2 gene. All of 5 PBMC RNA preparations tested were positive using unnested primers in S segment. Nucleotide sequences were determined for 16 G2 amplimers and 4 S segment amplimers, verifying that unique MCV cDNA sequences were amplified. Viral RNA became undetectable in 5 of 7 convalescent samples tested but was present up to day 23 of illness in 2 case-patients.

Characterization of human antibody responses to four corners hantavirus infections among patients with hantavirus pulmonary syndrome.

Hantavirus pulmonary syndrome (HPS) is a human disease caused by a newly identified hantavirus, which we will refer to as Four Corners virus (FCV). FCV is related most closely to Puumala virus (PUU) and to Prospect Hill virus (PHV). Twenty-five acute HPS serum samples were tested for immunoglobulin G (IgG) and IgM antibody reactivities to FCV-encoded recombinant proteins in Western blot (immunoblot) assays. All HPS serum samples contained both IgG and IgM antibodies to the FCV nucleocapsid (N) protein. FCV N antibodies cross-reacted with PUU N and PHV N proteins. A dominant FCV N epitope was mapped to the segment between amino acids 17 and 59 (QLVTARQKLKDAERAVELDPDDVNKSTLQSRRAAVSALETKLG). All HPS serum samples contained IgG antibodies to the FCV glycoprotein-1 (G1) protein, and 21 of 25 serum samples contained FCV G1 IgM antibodies. The FCV G1 antibodies did not cross-react with PUU G1 and PHV G1 proteins. The FCV G1 type-specific antibody reactivity mapped to a segment between amino acids 59 and 89 (LKIESSCNFDLHVPATTTQKYNQVDWTKKSS). One hundred twenty-eight control serum samples were tested for IgG reactivities to the FCV N and G1 proteins. Nine (7.0%) contained FCV N reactivities, 3 (2.3%) contained FCV G1 reactivities, and one (0.8%) contained both FCV N and FCV G1 reactivities. The epitopes recognized by antibodies present in control serum samples were different from the epitopes recognized by HPS antibodies, suggesting that the control antibody reactivities were unrelated to FCV infections. These reagents constitute a type-specific assay for FCV antibodies.