Platelet Count in Patients with Mild Disease at Admission is Associated with Progression to Severe Hantavirus Cardiopulmonary Syndrome

Background: Hantavirus cardiopulmonary syndrome (HCPS) has a mortality up to 35–40% and its treatment is mainly supportive. A variable to predict progression from mild to severe disease is unavailable. This study was performed in patients with documented infection by Andes orthohantavirus, and the aim was to find a simple variable to predict progression to moderate/severe HCPS in patients with mild disease at admission. Methods: We performed a retrospective analysis of 175 patients between 2001 and 2018. Patients were categorized into mild, moderate, and severe disease according to organ failure and advanced support need at hospital admission (e.g., mechanical ventilation, vasopressors). Progression to moderate/severe disease was defined accordingly. Clinical and laboratory variables associated with progression were explored. Results: Forty patients with mild disease were identified; 14 of them progressed to moderate/severe disease. Only platelet count was different between those who progressed versus those that did not (37 (34–58) vs. 83 (64–177) K/mm³, p < 0.001). A ROC curve analysis showed an AUC = 0.889 (0.78–1.0) p < 0.001, with a platelet count greater than 115K /mm³ ruling out progression to moderate/severe disease. Conclusions: In patients with mild disease at presentation, platelet count could help to define priority of evacuation to tertiary care centers.

Malaria and Hantavirus Pulmonary Syndrome in Gold Mining in the Amazon Region, Brazil

People living in mining regions are exposed to numerous biological agents by several specific types of transmission mechanisms. This study is designed to describe fatal hantavirus pulmonary syndrome (HPS) cases confirmed by serology and molecular analysis, where a seroprevalence survey was conducted in the gold mining regions of the state of Mato Grosso, in the official Amazon region, Brazil. Two fatal cases of HPS were confirmed in a mining area in the Legal Amazon, where malaria is one of the most important public health problems. A molecular analysis detected the presence of the genome of the Castelo dos Sonhos virus. Out of the 112 blood samples analyzed, five were positive for Plasmodium infection (four P. falciparum and one P. vivax), and four were seropositive for hantavirus, showing a seroprevalence of 3.57%. One of the four miners who was seroreactive for hantavirus concomitantly had P. falciparum infection, which was confirmed by thick blood smear. This manuscript highlights the importance of considering hantavirus pulmonary syndrome as a diagnostic possibility in febrile infection associated with pulmonary manifestations in mining areas where malaria cases are often identified.

Serum levels of interleukin-6 are linked to the severity of the disease caused by Andes Virus

Andes virus (ANDV) is the etiological agent of hantavirus cardiopulmonary syndrome in Chile. In this study, we evaluated the profile of the pro-inflammatory cytokines IL-1β, IL-12p70, IL-21, TNF-α, IFN-γ, IL-10 and IL-6 in serum samples of ANDV-infected patients at the time of hospitalization. The mean levels of circulating cytokines were determined by a Bead-Based Multiplex assay coupled with Luminex detection technology, in order to compare 43 serum samples of healthy controls and 43 samples of ANDV-infected patients that had been categorized according to the severity of disease. When compared to the controls, no significant differences in IL-1β concentration were observed in ANDV-infected patients (p = 0.9672), whereas levels of IL-12p70 and IL-21 were significantly lower in infected cases (p = <0.0001). Significantly elevated levels of TNF-α, IFN-γ, IL-10, and IL-6 were detected in ANDV-infected individuals (p = <0.0001, 0.0036, <0.0001, <0.0001, respectively). Notably, IL-6 levels were significantly higher (40-fold) in the 22 patients with severe symptoms compared to the 21 individuals with mild symptoms (p = <0.0001). Using multivariate regression models, we show that IL-6 levels has a crude OR of 14.4 (CI: 3.3–63.1). In conclusion, the serum level of IL-6 is a significant predictor of the severity of the clinical outcome of ANDV-induced disease.

Andes virus (ANDV) causes hantavirus cardiopulmonary syndrome (HCPS) that is characterized by the development of vascular leakage syndrome, eventually leading to massive pulmonary edema, shock and, in many cases, death. To date, no FDA-approved immunotherapeutics, specific antivirals, or vaccines are available for use against HCPS. Patient survival rates hinge largely on early virus diagnosis, hospital admission and aggressive pulmonary and hemodynamic support in an intensive care unit. Individual host factors associated with the outcome of an ANDV infection are poorly known, and such knowledge could allow the disease progression of hospitalized patients to be predicted, resulting in individualized treatment. In this study, we show that serum levels of IL-6 at the time of hospitalization in ANDV-infected patients are associated with the severity of the clinical outcome of ANDV-induced disease. Therefore, these finding suggest that determining IL-6 levels at the time of admission to the hospital could be useful to predict the progression of ANDV-induced disease.

[Hantavirus pulmonary syndrome in Buenos Aires, 2009-2014]

Andes virus is the causative agent of hantavirus pulmonary syndrome (HPS) in Argentina and neighboring countries. In our country four different areas are affected: Northwest, Southwest, Central and Northeast, where distinct Andes virus genotypes were characterized. Three genotypes were described in Buenos Aires province (Central area): AND-Buenos Aires, AND-Lechiguanas and AND-Plata. In this work, we considered all HPS cases confirmed by ELISA and real time RT-PCR during the period 2009-2014 in Buenos Aires province. The annual distribution, fatality rate and geographic distribution were analyzed. We also analyzed the genotypes involved by RT-PCR and nucleotide sequencing. Finally we evaluated epidemiological data in order to establish the route of transmission. We analyzed 1386 suspect cases of hantavirus infection from Buenos Aires province and we confirmed 88 cases of Hantavirus Pulmonary Syndrome during 2009-2014. The overall average was 14.3 cases per year. The occurrence of a HPS outbreak was confirmed in Buenos Aires province during 2013, showing a 3 fold increase in case number compared to the annual average between 2009 and 2012, tending to normalize during 2014. The overall lethality was 25.6%, with a maximum value of 45.5% in 2011. Genotype analysis was performed in 30.7% of confirmed cases, AND-BsAs show the highest incidence, it was characterized in 72% of the studied cases. Epidemiological data and results of viral genome comparison strongly suggest person-to-person transmission in the three clusters of two cases described in our study.

Imported hantavirus cardiopulmonary syndrome in an Italian traveller returning from Cuba

Hantavirus hemorrhagic fever with renal syndrome is endemic in Europe and Asia, while hantavirus cardiopulmonary syndrome (HCPS) is endemic in Northern, Central and Southern America. The first case of imported HCPS involving an Italian traveller returning from Cuba is reported.

Evaluation of an enzyme-linked immunosorbent assay based on Araraquara virus recombinant nucleocapsid protein

Laboratory diagnosis of hantavirus cardiopulmonary syndrome (HCPS) in Brazil has been performed mostly by detection of IgM antibodies to recombinant antigen purified from Sin Nombre virus and Andes virus (ANDV). Recently, a recombinant nucleocapsid (rN) protein of Araraquara virus (ARAV), a Brazilian hantavirus, was obtained in Escherichia coli. To evaluate ARAV rN as antigen for antibody detection, serum samples from 30 patients from Argentina seropositive for hantavirus were tested. All samples were positive for IgG and IgM by enzyme-linked immunosorbent assay (ELISA) using either ARAV rN or ANDV rN antigens. In Brazil, six of 60 serum samples from patients with suspected HCPS (10%) were positive for IgM by ELISA using ARAV rN antigen and 7 were positive using ANDV rN antigen. For results obtained with 90 serum samples analyzed by IgM ELISA with ANDV rN antigen, the sensitivity of the IgM ELISA using ARAV rN antigen was 97.2%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 98.1%. The results show that ARAV rN is a suitable antigen for diagnosis of hantavirus infection in Brazil and Argentina.

Cluster of cases of hantavirus pulmonary syndrome in Alberta, Canada

In May 2005, a cluster of four hantavirus pulmonary syndrome (HPS) cases was confirmed in Alberta, Canada. The cluster is unusual given that three cases were from a single family and involved a 7-year-old child. This is the first family cluster reported in Canada and includes one of the youngest cases of HPS reported in North America.

Clinical and laboratory findings related to a favorable evolution of hantavirus pulmonary syndrome

The medical records of 27 patients with hantavirus pulmonary syndrome were analyzed according to the need for invasive mechanical ventilation in relation to the following data up on hospital admission: age, gender, fever, cough, dyspnea, systolic arterial blood pressure, heart rate, levels of hemoglobin, hematocrit, leukocytes, lymphocytes, platelets, creatinine and arterial blood gases. The volume infused during the first 24 hours after admission, the use of inotropic agents, the use of corticosteroids and the patient outcomes were also evaluated. A favorable outcome was related to systolic blood pressure³ 100mmHg, heart rate lower than 100 beats per minute, creatinine below 1.6mg/dl, arterial blood pH³ 7.35, bicarbonate higher than 15mEq/dl, oxygen saturation higher than 84.1%, lower rehydration volume in the first 24 hours of hospitalization and no use of inotropic agents. Absence of clinical and laboratory signs of circulatory shock up on admission was associated with a favorable outcome of the patients.

Neutralizing antibodies in survivors of Sin Nombre and Andes hantavirus infection

We evaluated titers of homotypic and heterotypic neutralizing antibodies (NAbs) to Andes and Sin Nombre hantaviruses in plasma samples from 20 patients from Chile and the United States. All but 1 patient had high titers of NAb. None of the plasma samples showed high titers against the heterologous virus.

Hantavirus pulmonary syndrome in Central Bolivia: relationships between reservoir hosts, habitats, and viral genotypes

In August 2002, two cases of hantavirus pulmonary syndrome (HPS) were confirmed in Mineros and Concepcion, within the Santa Cruz Department of Bolivia. Extensive alteration of the native ecosystem, from dense forest to pasture or sugarcane, had occurred in both regions. An ecologic assessment of reservoir species associated with the human disease identified a single hantavirus antibody-positive Oligoryzomys microtis from Mineros and three hantavirus antibody-positive Calomys callosus from Concepcion. In Mineros, the virus from the O. microtis was 90% similar to sequences published for Rio Mamore virus. Viral nucleotide sequences from two C. callosus were 87-88% similar to the sequence of Laguna Negra virus. The viral sequence from the C. callosus was 99% identical to viral sequences obtained from the HPS patient in this area, implicating C. callosus as the host and Laguna Negra virus as the agent responsible for the HPS case near Concepcion.

Hantavirus pulmonary syndrome in northwestern Argentina: circulation of Laguna Negra virus associated with Calomys callosus

The purpose of this study was to characterize the hantaviruses circulating in northwestern Argentina. Human and rodent studies were conducted in Yuto, where most cases of hantavirus pulmonary syndrome (HPS) occur. Partial virus genome sequences were obtained from the blood of 12 cases of HPS, and from the lungs of 4 Calomys callosus and 1 Akodon simulator. Phylogenetic analysis showed that three genotypes associated with HPS circulate in Yuto. Laguna Negra (LN) virus, associated with C. laucha in Paraguay, was identified for the first time in Argentina; it was recovered from human cases and from C. callosus samples. The high sequence identity between human and rodent samples implicated C. callosus as the primary rodent reservoir for LN virus in Yuto. The genetic analysis showed that the Argentinian LN virus variant differed 16.8% at the nucleotide level and 2.9% at the protein level relative to the Paraguayan LN virus. The other two hantavirus lineages identified were the previously known Bermejo and Oran viruses.

Neutralizing antibodies and Sin Nombre virus RNA after recovery from hantavirus cardiopulmonary syndrome

Patients who later have a mild course of hantavirus cardiopulmonary syndrome (HCPS) are more likely to exhibit a high titer of neutralizing antibodies against Sin Nombre virus (SNV), the etiologic agent of HCPS, at the time of hospital admission. Because administering plasma from patients who have recovered from HCPS to those in the early stages of disease may be an advantageous form of passive immunotherapy, we examined the neutralizing antibody titers of 21 patients who had recovered from SNV infection. Even 1,000 days after admission to the hospital, 6 of 10 patients had titers of 800 or higher, with one sample retaining a titer of 3,200 after more than 1,400 days. None of the convalescent-phase serum samples contained detectable viral RNA. These results confirm that patients retain high titers of neutralizing antibodies long after recovery from SNV infection.

[Hantavirus pulmonary syndrome: current situation among rodent reservoirs and human population in the 10th region, Chile]

BACKGROUND

In Chile, three Hantavirus seropositive rodent species (O longicaudatus, A olivaceus and A longipilis) are distributed from the Pacific coast to the Andes mountains and represent nearly 90% of the rodents captured in the Xth Region.

AIM

To study the seroprevalence of Hantavirus among captured rodent species and its relationship with the appearance of human cases of pulmonary syndrome.

MATERIAL AND METHODS

From May 1998 to September 2001, 675 rodents were captured in the region. Serum samples were tested by ELISA for the presence of IgG antibodies against Andes and Sin Nombre virus. Sera from human cases with a suspected Hantavirus infection were analyzed for IgM antibodies against Black Lagoon virus and for IgG antibodies against Andes and Sin Nombre virus.

RESULTS

Twenty two of the 675 rodents were seropositive for the virus, 18 O longicaudatus and 4 A longipilis. Regional seroprevalence changed from 2.2% in 1998, 0.0% in 1999, 1.0% in 2000 and up to 7.1% in 2001. A total of 77 positive human cases were studied from 1998 to March 2002. Although there were positive cases in all seasons, data showed a spring-summer seasonal preponderance. A relationship between the flowering of "colihue" bushes and the increased values of rodent abundance, seroprevalence and positive animals was established.

CONCLUSIONS

A dispersal movement of O longicaudatus to open habitats close to human outdoor activities during the dry season was confirmed.

[Hantavirus in human and rodent population in an endemic area for hantavirus pulmonary syndrome in Argentina]

This paper analyzed the prevalence and distribution of serological reactivity to hantavirus (antibody against ANDES virus) of human population exposed to hantavirus and rodents trapped in the studied area. This study was developed in Salta (Orán and San Martín Departments), area with the highest incidence for Hantavirus Pulmonary Syndrome (HPS) in Argentina. In December 1997, 453 healthy people were studied by serology and 39 rodents by serology and PCR. The studied individuals were distributed as: 145 farm inhabitants (FI), 212 people living in the same dwelling with healthy individuals (controls) (Cco), 87 people living in the same dwelling with persons undergoing SPH in 1997 (cases) (Cca). Moreover, 19 physicians and nurses who cared for patients with SPH in 1997 were also studied. The prevalence of hantavirus infection among the studied population was 6.3%. The prevalence was 10.3% among FI, 6.9% among Cca and 3.3% among Cco (p < 0.02). There was no serological reactivity among PS. The prevalence in 39 trapped rodents was 10.2%, with infection only for Oligoryzomys chacoensis, O. flavescens and Akodon varius species. The prevalence of human cases with asymptomatic infection in Salta is higher than in other regions of the country, and we are presenting a hypothesis to explain these differences. The analyzed data suggest that in this region up to the time this study was performed, there would not have been person to person transmission of hantavirus. The transmission would be from rodent contact exclusively and mainly in ongoing deforestation areas and domestic habitat surrounding rural dwellings.

[Seroprevalence of antibodies against hantavirus in 10 communities of the IX Region of Chile where hantavirus infection were diagnosed]

BACKGROUND

Thirty six cases of clinical Hantavirus Cardiopulmonary Syndrome occurred in the IX Region of Chile. Most of these patients were young males, farm or timber workers, who lived near the Andes Mountain chain.

AIM

To conduct an epidemiological and serosurvey study to determine the seroprevalence of IgG antibodies against Hantavirus in the general adult population living in rural and urban areas of 10 endemic communities of the IX region of Chile.

MATERIAL AND METHODS

A total of 400 subjects were included, 40 of each community, 20 rural residents and 20 urban residents, 20 males and 20 females.

RESULTS

Seroprevalence was 7.5% in Melipeuco, 5.0% in Lonquimay, 2.5% in Curacautin, 2.5% in Pucón and 0.0% in the remaining communities. Seroprevalence was higher in rural population (2.5%) than in the urban areas (1%). All seropositive subjects worked in farms or forests and observed rodents near their homes or working places. Females were affected the same as males and no differences were observed between Chilean natives and Hispanics.

CONCLUSIONS

Prevalence of Hantavirus antibodies correlated with the geographic zone (Andes Mountain chain), overgrowth of wild rodents and exposure to rodent-infested environments.

Rapid presumptive diagnosis of hantavirus cardiopulmonary syndrome by peripheral blood smear review

Hantavirus cardiopulmonary syndrome (HCPS) is a rare but frequently lethal acute zoonotic viral infection in rural North America. The rapidity of progression from febrile prodrome to cardiogenic shock and noncardiogenic pulmonary edema requiring intensive care creates high diagnostic urgency and a need for a rapid screening tool. In this retrospective cohort study, 2 pathologists scored blinded peripheral blood smears from 52 patients with HCPS and 128 seronegative patients referred for diagnosis of suspected hantavirus infection. During the prodromal phase, thrombocytopenia was the only consistent abnormality and could be used to indicate hantavirus serologic testing. After the onset of pulmonary edema detected radiographically, the presence of 4 of 5 findings (thrombocytopenia, myelocytosis, hemoconcentration, lack of significant toxic granulation in neutrophils, and more than 10% of lymphocytes with immunoblastic morphologic features) has a sensitivity for HCPS of 96% and a specificity of 99% and missed no patients with HCPS who required intensive care. While each abnormality is commonly seen, the combination of at least 4 of these CBC count data and peripheral blood smear findings can guide early treatment and patient transport decisions until rapid, specific, serologic testing becomes widely available.

[Hantavirus pulmonary syndrome in Buenos Aires Province]

In Argentina the first Hantavirus Pulmonary Syndrome (HPS) cases were characterized in 1995. Since then, Argentina is the country with the highest number of notified cases in South America. The disease is distributed in Northern, Southern and Central regions of the country, being Buenos Aires the most affected province from the Central region. In this study, we present seasonal and geographical distribution of HPS cases in Buenos Aires province, the association with diverse viral lineages and the serological characteristics of hantavirus infection in the period from 1997 up to the first semester of the year 2000. An increase in the number of HPS cases was observed up to 1999 and a gradual mortality decrease in the whole period. The cases occurred between spring and autumn, with a maximum peak in summer. The serological response was studied in 58 HPS confirmed cases at different times after the onset of symptoms. The cases were distributed between 27 localities, in two different directions from the city of Buenos Aires: South-southwest and North-northeast. More than 52% of the cases occurred in La Plata and neighboring localities. The viral genomes from 39 cases were all characterised as Andes virus (AND): AND Cent Plata 16%; AND Cent 21% and AND Cent Bs.As. 60%. Andes virus lineages only cocirculated in La Plata city. These results will contribute to establish a risk map leading to the implementation of improved strategies of prevention.

Humoral immune responses in the hantavirus cardiopulmonary syndrome

The immunologic responses that mediate viral clearance of and recovery from hantavirus cardiopulmonary syndrome (HCPS) due to Sin Nombre (SN) virus are unknown. Serial serum samples from 26 patients with acute SN virus infection were tested for IgG, IgA, and IgM reactivity to recombinant viral nucleocapsid (N) and glycoprotein G1 antigens by a novel strip immunoblot assay. The titers of antibodies capable of neutralizing SN virus in vitro also were determined for each sample. At admission, patients with severe disease had lower titers of IgG antibodies to SN virus N antigen (P<.033) and lower neutralizing antibody titers (P<3.4x10-5), compared with patients with mild disease. These data suggest that a strong neutralizing antibody response may be a predictor of effective clearance of and recovery from SN virus infection and raise the possibility that passive immunotherapy may be useful in HCPS.

Hantavirus pulmonary syndrome in Brazil: clinical aspects of three new cases

Hantavirus pulmonary syndrome (HPS) has been recognized recently in Brazil, where 28 cases have been reported as of September 1999. We report here the clinical and laboratory findings of three cases whose diagnoses were confirmed serologically. All the patients were adults who presented a febrile illness with respiratory symptoms that progressed to respiratory failure that required artificial ventilation in two of them. Laboratory findings were most of the time consistent with those reported in the United States in patients infected with the Sin Nombre virus, and included elevated hematocrit and thrombocytopenia; presence of atypical lymphocytes was observed in one patient. The chest radiological findings observed in all the patients were bilateral, diffuse, reticulonodular infiltrates. Two patients died. Histopathological examination of the lungs of these patients revealed interstitial and alveolar edema, alveolar hemorrhage, and mild interstitial pneumonia characterized by infiltrate of immunoblasts and mononuclear cells. In the epidemiologic investigation of one of the cases, serologic (ELISA) tests were positive in 3 (25%) out of 12 individuals who shared the same environmental exposure. HPS should be included in the differential diagnosis of interstitial pneumonia progressing to acute respiratory failure.

New York 1 and Sin Nombre viruses are serotypically distinct viruses associated with hantavirus pulmonary syndrome

New York 1 virus (NY-1) and Sin Nombre virus (SN) are associated with hantavirus pulmonary syndrome (HPS). NY-1 and SN are derived from unique mammalian hosts and geographic locations but have similar G1 and G2 surface proteins (93 and 97% identical, respectively). Focus reduction neutralization assays were used to define the serotypic relationship between NY-1 and SN. Sera from NY-1-positive Peromyscus leucopus neutralized NY-1 and SN at titers of >/=1/3,200 and 16-fold-lower neutralizing titers to NY-1 than to SN. Reference sera to Hantaan, Seoul, and Prospect Hill viruses also failed to neutralize NY-1. These results indicate that SN and NY-1 define unique hantavirus serotypes and implicate the presence of additional HPS-associated hantavirus serotypes in the Americas.

Assessment of person-to-person transmission of hantavirus pulmonary syndrome in a Chilean hospital setting

Person-to-person transmission of Andes hantavirus among healthcare workers was reported in Argentina for the first time in 1996. To determine whether such transmission of the virus occurred during a 1997 outbreak of hantavirus pulmonary syndrome (HPS) in southern Chile due to Andes virus, we conducted a serological and epidemiological study in the Coyhaique Regional Hospital, where the majority of HPS patients were admitted. Workers in every department of the hospital were evaluated for immunoglobulin G (IgG) and IgM hantavirus antibodies using the enzyme-linked immunosorbent assay (ELISA). A standardized questionnaire was used to determine the type and extent of exposure to HPS patients, as well as other potential risk factors and previous febrile respiratory illnesses requiring hospitalization. Less than half (44%) reported always using gloves when touching patients or their secretions; respiratory protection was not used. Of the 319 participants (87.9% of those eligible), 12 (3.7%) had IgG antibodies. This finding is consistent with the antibody prevalence in the community in which the participants lived. Of the 12 positive healthcare workers, six reported contact with HPS patients. A similar exposure was found in those who tested negative [6/140 (4%) compared to 6/179 (3%), P = 0.66]. There was no significant difference in the types of hospital activities performed or the number of hospitalizations for febrile respiratory illnesses between antibody-positive and antibody-negative individuals. These data suggest that there was no person-to-person transmission among healthcare workers during a recent outbreak of HPS in Southern Chile in 1997, despite the inconsistent use of any precautions against transmission.

Hantavirus pulmonary syndrome: CD8+ and CD4+ cytotoxic T lymphocytes to epitopes on Sin Nombre virus nucleocapsid protein isolated during acute illness

In 1993 a number of cases of unexplained adult respiratory syndrome occurred in the southwestern United States. The illness was characterized by a prodrome of fever, myalgia, and other symptoms followed by the rapid onset of a capillary leak syndrome with hemoconcentration, thrombocytopenia, and pulmonary edema. Viral RNA sequences in the lungs identified a new member of the hantavirus genus, Sin Nombre virus (SNV), unique to North America. Pulmonary endothelial cells were heavily infected but were not necrotic. We speculated that this capillary leak syndrome was initiated by immune responses to the SNV-infected pulmonary endothelial cells. We isolated a CD8+ cytotoxic T lymphocyte (CTL) clone directly from the blood of a patient with the acute hantavirus pulmonary syndrome (HPS) which recognizes a SNV specific epitope on the virus nucleocapsid protein (aa 234-242) that is restricted by HLA C7 and produces IFN gamma but not IL-4. We identified a second CD8+ CTL epitope located within another site aa 131-139 on the nucleocapsid protein, which is HLA B35 restricted, and a CD4+ CTL epitope located on a third site on nucleocapsid protein aa 372-380 using lymphocytes obtained during HPS from another patient that were stimulated in vitro. Hantavirus specific CD8+ and CD4+ CTL may contribute to the immunopathology and capillary leak syndrome observed in the HPS.

Hantavirus pulmonary syndrome. Report of the first three cases in São Paulo, Brazil

The hantavirus pulmonary syndrome was first recognized in cases that occurred in the U.S. in 1993, which served as an alert not only for American physicians but also for physicians in other countries for the identification of the disease. In the city of São Paulo, Brazil, 3 cases of the syndrome were recorded in 1993. The patients were young brothers residing in the Mata Atlântica (Atlantic Forest) region submitted to recent deforestation. Two of the patients died of acute respiratory insufficiency and the third recovered without sequelae. In the surviving patient the diagnosis was established by a laboratory criterion based on the detection of specific IgM and IgG class antibodies by indirect immunofluorescence. In the two patients who died, the diagnosis was confirmed by laboratory tests using immunoperoxidase technique for hantavirus in tissue, in histological lung and heart sections in one case, and by clinical and epidemiological data in the other.

Clinical features that differentiate hantavirus pulmonary syndrome from three other acute respiratory illnesses

To elucidate the early clinical characteristics of hantavirus pulmonary syndrome (HPS), we compared the clinical features of 24 cases of HPS with those of cases of bacteremic pneumococcal pneumonia (n = 30), influenza (n = 33), or unexplained adult respiratory distress syndrome (ARDS, n = 21). On admission, patients with HPS were less likely than outpatients with influenza to have reported sore throat (OR = 0.02, P < .01) and cough (OR = 0.1, P = .01) and were less likely than patients with pneumococcal pneumonia to have lobar infiltrates detected by chest roentgenography (OR = 0, P < .01). Multivariate discriminant analysis revealed that three clinical characteristics at admission (dizziness, nausea or vomiting, and absence of cough) and three initial laboratory abnormalities (low platelet count, low serum bicarbonate level, and elevated hematocrit level) served to identify all patients with HPS and to exclude HPS in at least 80% of patients with unexplained ARDS. These findings warrant further study and should facilitate the early recognition of patients with HPS, who may benefit from early critical-care intervention.

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.