Hantaviruses, transmitted from rodents to human. Hantavirus Pulmonary Syndrome Due to Andes Virus in Temuco, Chile* Clinical Experience With 16 Adults

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1 Hantavirus Pulmonary Syndrome Due to Andes Virus in Temuco, Chile* Clinical Experience With 16 Adults Constanza Castillo, MD; Jorge Naranjo, MD; Alvaro Sepúlveda, MD; Gonzalo Ossa, MD; and Howard Levy, MD, PhD, FCCP Study objectives: To describe the clinical features and laboratory abnormalities of 16 adults with confirmed Hantavirus pulmonary syndrome (HPS) due to Andes virus in Temuco, Chile. Design: A retrospective chart review abstracting clinical, radiologic, laboratory, and epidemiologic data. Setting: ICU of the university teaching hospital in Temuco, Chile. Patients: Sixteen patients with HPS treated between 1997 and Results: Patients were aged from 19 to 45 years, 82% were men, and 88% were farm or timber workers with occupational acquisition of HPS. After an incubation period ranging from 5 to 25 days, a prodromal influenza-like phase frequently was accompanied by abdominal symptoms. From 1 to 7 days later, respiratory insufficiency and hemodynamic instability suddenly appeared. In 81%, hemorrhage was evident; in 63%, moderate-to-severe bleeding occurred. The most prominent laboratory abnormalities were hemoconcentration, leukocytosis, thrombocytopenia, altered partial thromboplastin time (PTT), creatine kinase, transaminases, and hyponatremia. Creatinine elevation was common, with clinical importance in two patients. All patients had severe hypoxemia and pulmonary edema. Fifteen patients received supportive treatment, and 5 patients were treated with corticosteroids. The mortality rate was 43.8%. Conclusions: Bad prognostic factors appeared to be severe hypotension, lower PaO 2 /fraction of inspired oxygen values, prolonged PTT, hemorrhage, greater volume load, and profuse bronchorrhea. The effects of treatment with corticosteroids could not be determined. Hemorrhage and renal involvement were common in our patients, features not often described in the North American literature of Sin Nombre virus HPS. (CHEST 2001; 120: ) Key words: Andes virus; Hantavirus pulmonary syndrome; hemorrhagic disorders; South American Hantavirus Abbreviations: ALT alanine aminotransferase; AST aspartate aminotransferase; CDC Centers for Disease Control and Prevention; CI cardiac index; CK creatine kinase; ELISA enzyme-linked immunosorbent assay; Fio 2 fraction of inspired oxygen; HPS Hantavirus pulmonary syndrome; LDH lactate dehydrogenase; PAOP pulmonary artery occlusion pressure; PTT partial thromboplastin time; SVRI systemic vascular resistance index Hantaviruses, transmitted from rodents to human beings, can cause two different syndromes: the hemorrhagic fever renal syndrome described in Asia and Europe, and the Hantavirus pulmonary syndrome (HPS) without hemorrhage described in 1993 in the southwestern United States HPS was *From the Department of Internal Medicine (Drs. Castillo, Naranjo, Sepúlveda, and Ossa), Temuco Teaching Hospital and Faculty of Medicine Universidad de la Frontera, Temuco, Chile; and University of New Mexico Health Sciences Center (Dr. Levy), Albuquerque, NM. Financed by the Universidad de la Frontera Temuco, Chile. Registration No. 99/110. Manuscript received June 23, 2000; revision accepted January 23, Correspondence to: Constanza Castillo, MD, Department of Internal Medicine, Medicine Faculty, Universidad de la Frontera, M. Montt 116 Temuco, Chile; eureka@telsur.cl identified as a seemingly new human infectious disease caused by variants of Hantaviruses: Sin Nombre virus; Bayou, NY; and Black Creek Canal virus This infectious disease has an influenza-like prodromal stage, but can progress to a catastrophic hemodynamic failure and pulmonary edema In 1994, isolated cases of HPS were reported in Brazil, followed by nearly 20 cases in Paraguay. In 1995, an epidemic outbreak began in the southern part of Argentina and Chile. 17 It is believed that climate changes, related to El Niño oceanic stream, favored the overgrowth of rodents in rural areas, especially in the Andes mountain chains. A new strain of Hantavirus was identified and called Andes virus, with the primary host, the wild rat Oligoryzomys longicaudatus Clinical Investigations in Critical Care

2 In Temuco, Chile, 20 serologically confirmed cases (positive IgM antibodies detected by enzymelinked immunosorbent assay [ELISA] following the Centers for Disease Control and Prevention [CDC] guidelines) 21 of HPS have been treated: 16 adults and 4 children. We describe the epidemiologic and clinical features of the 16 adults. Materials and Methods A retrospective chart review of all the adult patients with confirmed HPS admitted between 1997 and 1999 to the ICU of the Temuco Teaching Hospital (the authors own institution) was performed after the approval of the ethics committee of the hospital. HPS was confirmed by measurement of IgM antibodies using ELISA according to the guidelines of the CDC, and with antigens of Sin Nombre virus provided by the CDC. The ELISA tests were conducted in the central virology laboratory of the Ministry of Health, Santiago, Chile, by professionals trained in special techniques for Hantaviruses at the CDC. The clinical charts were reviewed by the authors who also attended the patients and conducted the treatment procedures. Laboratory measurements were done using the same technique in all patients at the Temuco Hospital laboratory. The chest radiographs were interpreted by the attending physician at the ICU, and conclusions were confirmed by a radiology consultant. Epidemiologic data were produced by personnel of the Ministry of Health with expertise in epidemiology of infectious diseases who researched the most probable place and time of the HPS acquisition in each of the HPS cases, using a three-pathway model based on clinical histories, the account of their relationships, and information from coworkers. They also visited the most probable sites of HPS acquisition to verify the contagion in a specific site. The incubation period was estimated based on this information. Two-sample Wilcoxon rank-sum (Mann-Whitney) test or Fisher s Exact Test was performed, and p 0.05 was considered statistically significant. Results The diagnosis was suspected in face of an influenzalike illness or acute fever (temperature 38 C ) associated with GI symptoms in patients who worked or had been housed in places highly infested with rodents. A chest radiograph with interstitial infiltrates or effusions suggesting pulmonary edema and an elevated hematocrit ( 45%), leukocytosis ( / L), and/or thrombocytopenia ( / L) suggested the diagnosis in the early stage of the disease. A common triad was pulmonary edema, hypotension (systolic BP 120 mm Hg), and hemoconcentration. IgM and IgG antibodies against Hantavirus by ELISA were measured at the virology laboratory of the Ministry of Health, using antigens of Sin Nombre virus, provided by the CDC. In 16 adults, the diagnosis of HPS was serologically confirmed. The HPS affected predominantly farm or timber workers who were exposed to highly infested environments in the workplace (88%): nine patients worked in enclosed environments (storage buildings), two individuals became ill after working in the deep forest, and two women who worked as managers of camping places in the Andes national parks were infected after cleaning up previously abandoned facilities. Two tourists became ill after lodging in uninhabited cottages, and one man became ill after cleaning and repairing a harvesting machine that was infested by rats. No patient seemed to become infected in his or her own home. The mean age of the patients was 30 years (range, 19 to 45 years), 82% were men, 88% were Hispanics, and 12% were South American natives. The estimated incubation period was calculated based on the most probable place and time of infection reported by the epidemiologists of the Ministry of Health, and ranged between 5 and 25 days. The mean period of the prodromal symptoms was 4 days (range, 1 to 7 days). All suffered from fever and myalgia, 50% had GI symptoms, 30% had headache, 30% had dry cough, 25% had back pain, and 13% had dizziness, polyarthralgia, and odynophagia. One patient had diarrhea, another had conjunctival injection, and one had a maculopapular rash. From 1 to 7 days (mean, 4 days) after the initial prodromal symptoms, sudden hypotension (systolic BP 120 mm Hg) and respiratory distress appeared. During the advanced stage of the illness, the most common findings were tachycardia ( 100 beats/min), tachypnea ( 25 breaths/min), and cough (100%). Hypotension and fever were present in 94%. One patient was hypothermic (temperature 35 C) at the time of ICU admission. Bleeding disorders were seen in 81% of the patients during the advanced state of the disease (Tables 1, 2). Major external bleeding ( 500 ml) was observed in 63% of the cases. All six fatal cases had clinical evidence of bleeding (Tables 1, 2). Laboratory Blood samples for laboratory data were available in 15 of the 16 patients. The average number of Table 1 Clinical Evidence of Bleeding in Patients With HPS* Site of Bleeding Patients, No. % Hematuria 8 50 Hemoptysis 4 25 Puncture sites 4 25 Hematemesis 3 19 Epistaxis 2 13 Oral mucosa 1 6 Hemothorax 1 6 Lung hemorrhage 1 6 Total *Nine patients bled from more than one source. CHEST / 120 / 2/ AUGUST,

3 Table 2 Clinical Hemorrhage in 13 of 16 Patients With HPS* Patient No. Day When Bleeding Started Maximum PTT, s Nadir Platelet Count, 10 3 / L Bleeding Sites Bleeding Severity Outcome Hematuria Mild Survived Hematuria Mild Survived 3 4 NA 16 Hematuria Mild Survived Hematuria Moderate Survived Punctures sites Hematuria Moderate Survived Puncture sites Hematuria Moderate Survived Epistaxis Hematemesis Moderate Survived Oral mucosa Hemoptysis Moderate Fatal Hematemesis Hematemesis Moderate Fatal Puncture sites Hematuria, epistaxis Severe Fatal Hemoptysis, hematemesis Puncture sites Hematuria Severe Fatal Hemoptysis Lung hemorrhage Hemoptysis Severe Fatal Hemothorax 13 4 NA NA Large hemothorax Severe Fatal *NA not available. Day after initial prodromal symptoms. Six patients with bleeding died. Mild 200 ml (self-limited); moderate 200 to 500 ml/24 h (no transfusion needed); severe 500 ml/24 h (transfusion necessary). Hemothorax was iatrogenic after puncture of the jugular vein. samples taken daily for laboratory tests in each patient was three, in the first 48 h of admission to the ICU. In a few cases, some of the laboratory results were not available in the patient s chart. We analyzed the worst laboratory values of each patient at the day of ICU admission (Tables 3, 4). All patients had hemoconcentration (hematocrit range, 48 to 70%). The platelet count was / L in 94% (range, 12 to / L). Leukocytosis was observed in 94% (Table 3). In 87% of our patients, the triad of hemoconcentration, low platelet count, and leukocytosis was present. The partial thromboplastin Table 3 Worst Laboratory Results on the Day of Admission To The ICU Laboratory Test Available, No. Abnormal Results, No. Mean Value Range Normal Values Hematocrit, % (male patients), 42 5 (female patients)* Platelet count, 10 3 / L WBC count, 10 3 / L PTT, s LDH, IU/L 9 9 1, , AST, IU/L ALT, IU/L CK, IU/L , Creatinine, mg/dl Amylase, IU/L Hyponatremia, meq/l Hypernatremia, meq/l *Values presented as mean SD. 550 Clinical Investigations in Critical Care

4 Table 4 Clinical Features and Laboratory Results on the Day of ICU Admission in Survivors vs Nonsurvivors* Variables Survivors (n 9) Nonsurvivors (n 7) p Value Systolic BP, mm Hg 116 (90 148) 81 (0 120) Pao 2 /Fio 2,mmHg 222 (96 130) 55 (44 68) Highest hematocrit, % 54 (48 61) 58 (50 70) Maximum PTT, s 78 (42 185) 110 (69 185) Lowest platelet count, 10 3 / L 53 (14 200) 37 (12 84) Maximum WBC count, 10 3 / L 23 (6 45) 23 (12 42) Serum creatinine 1.4 ( ) 1.3 ( ) Hyponatremia 123 ( ) 124 ( ) Patients receiving mechanical ventilation, No. Patients receiving vasoactive drugs, No. IV fluids in first 24 h, L 2.4 (1 4) 4.5 ( ) Patients receiving methylprednisolone, No *Data are presented as mean value (range) unless otherwise indicated. Fisher s Exact Test was performed, and p 0.05 was considered statistically significant. Statistically significant even when Bonferroni correction for multiple comparisons is made. One patient was in cardiac arrest at arrival and received no further treatment. time (PTT) was measured in 14 patients, and the values were prolonged in all of them (Table 3). Creatinine levels were high in 54% of our patients (Table 3). Eleven of 12 patients showed high levels of aspartate aminotransferase (AST) as well as alanine aminotransferase (ALT); in 9 patients, the lactate dehydrogenase (LDH) concentration was high (Table 3). In all eight patients, levels of creatine kinase (CK) were increased (Table 3). One patient had high levels of amylase (Table 3). In 69%, hyponatremia between 114 meq/l and 123 meq/l was found. One patient had hypernatremia (157 meq/l). In only 3 of 13 patients, the serum sodium concentration was normal (132 to 134 meq/l; Table 3). Urinalysis was performed in 15 patients. In five patients, a RBC count on urinalysis confirmed the clinical report of hematuria (Table 2). In three additional samples, the RBC count was high ( 10 RBCs per high-power microscopic field or 50/mL) indicating microscopic hematuria (Table 2). None of these eight patients underwent urinary catheterization before the specimen was obtained. Arterial blood gas analyses were available in 14 patients. Thirteen of them showed hypoxemia and one had hypoxemia with carbon dioxide retention (Paco 2, 72 mm Hg). The mean ratio of Pao 2 to the fraction of inspired oxygen (Fio 2 ) was 139 mm Hg at the day of ICU admission (range, 44 to 296 mm Hg; Table 4). The patient who died without arterial blood gas measurement had an oxygen saturation 70% on 100% oxygen. In all cases, the laboratory results showed the most altered values during the first 24 to 48 h of the cardiopulmonary stage and improvement thereafter within 4 to 7 days in the survivors. Chest Radiographs All chest radiographs showed diffuse interstitial infiltrates with Kerley B lines at the beginning of the cardiopulmonary stage. In the seven patients who died, the infiltrates worsened in 2 to 24 h to a massive pulmonary edema. In the nine patients who survived, the radiologic shadows worsened slowly in a period of 1 to 5 days (average, 2 days) but cleared rapidly thereafter in 3 to 4 days without residual changes. One patient developed a large spontaneous hemothorax. Pleural effusions in the other patients were not evident on the chest radiographs. Treatment All patients received oxygen between 0.4 and 1.0 Fio 2, and 69% received mechanical ventilation with 7 ml/kg tidal volume and positive end-expiratory pressure levels ranging from 5 to 12 cm H 2 O. All patients received IV fluids. The mean volume administered on the day of ICU admission was 3.2 L (range, 1 to 10.6 L; Table 4). Vasoactive drugs were administered to 10 hypotensive patients (dobutamine, dopamine, epinephrine, phenylephrine, and norepinephrine). Monitoring with a pulmonary artery (Swan-Ganz) catheter was possible in five patients receiving dopamine or associated vasoactivedrugs and parenteral volume (four survivors and one nonsurvivor). The pulmonary artery occlusion pressure (PAOP) was normal at ICU admission in four of these five patients (4 to 12 mm Hg), and one of them had PAOP of 19 mm Hg after vigorous volume loading. The PAOP rose at the nadir of the cardiopulmonary stage in three patients (16 to 19 mm Hg). One survivor and one nonsurvivor had decreased systemic vascular resistance index (SVRI): 1,289 dyne s/cm 5 m 2 and 1,678 dyne s/cm 5 m 2, respectively (normal range, 1,700 to 2,500 dyne s/cm 5 m 2 ) with normal cardiac index (CI) at ICU admission (normal range, 2.5 to 4.2 L/min/m 2 ). A third patient showed a slightly increased SVRI (2,729 dyne s/cm 5 m 2 ) with normal CI at ICU admission. After administration of vasoactive drugs, the SVRI increased slightly, but the CI dropped in all these three patients at the nadir of the cardiopulmonary stage (1.63 L/min/m 2, 1.94 L/min/m 2, and 1.94 L/min/m 2, respectively). The other two patients continued with normal hemodynamic values. In five patients, who responded rapidly to volume loading and the administration of dopamine, the insertion of a pulmonary catheter was CHEST / 120 / 2/ AUGUST,

5 avoided. In other five critically ill patients (four of them with hemorrhages), the insertion of a central catheter was extremely difficult and not possible in three patients. One patient was admitted to the ICU in cardiopulmonary arrest. Methylprednisolone was administered to five patients (1 g the first day, 500 mg the second and third days, and 250 mg on the fourth and fifth days). Clinical Course Seven of the 16 patients died, giving a case fatality rate of 43.8% (Table 4). The nonsurvivors had lower systolic BP at the time of ICU admission and severe hypoxemia; the Pao 2 /Fio 2 ranged from 44 to 68 mm Hg (mean, 55 mm Hg; Table 4). The PTT, platelet count, and other laboratory test results were more severely abnormal in the nonsurvivor group (Table 4). Six of the 7 patients who died had major external bleeding (Table 2). Platelet counts and PTT values did not predict the appearance of bleeding or the severity of the hemorrhage, but were less deranged in three patients who had no bleeding (mean PTT, 78 s vs 97 s; nadir platelet count, / L vs / L). The fluid volume administered in the patients who died was larger than in the survivors (Table 4). Four of the patients, who did not survive, were in refractory circulatory collapse and probably received excessive IV fluids ( 4 L; Table 4). These patients eliminated large amounts of serous fluid through the endotracheal tube at the ICU admission day (up to 3 L in one patient); this bronchial secretion was not seen in the survivors (Table 4). In 10 hypotensive patients (4 survivors and 6 nonsurvivors), vasoactive drugs were administered. Five of the nine survivors received mechanical ventilation as well as six of seven nonsurvivors (Table 4). The one patient who did not receive mechanical ventilation and died was admitted in cardiorespiratory arrest and died before he was connected to the ventilator. Five of nine survivors received methylprednisolone (Tables 4, 5). The most frequent complication was bleeding (81%; Tables 1, 2, 5). Ten patients (63%) had moderate or severe hemorrhages ( 500 ml), and 9 patients bled from more than one source. In two patients, severe intrathoracic hemorrhage was diagnosed at the autopsy (lung hemorrhage in one and a large spontaneous hemothorax in another). One patient who survived had sinus bradycardia (50 beats/ min) and nodal rhythm (30 beats/min) early in the cardiopulmonary stage. Three of the patients who died had transient ventricular tachycardia or fibrillation very late in the course of the disease. Severe sinus bradycardia or electromechanical dissociation preceded death in all. Two patients presented with renal insufficiency, and one of them needed transient hemodialysis. One patient developed high levels of amylase (Table 3), but no clinical evidence of pancreatitis was observed. Hyponatremia was a common finding (Table 3). Discussion The clinical features of our 16 patients with HPS caused by the Andes Hantavirus showed some differences with those described in the North American literature In the prodromal stage of the disease, one of our patients presented with bilateral conjunctival injection, as described with the Argentinian etiologic agent 22 and a second patient displayed a maculopapular rash. This patient had received paracetamol and amoxicillin after the initial symptoms. Table 5 Clinical Features and Laboratory Results on the Day of ICU Admission in Survivors by Corticosteroid Treatment* Clinical Features No Steroids (n 4) Metylprednisolone (n 5) p Value Minimum systolic BP, mm Hg 113 (90 130) 118 ( ) Minimum Pao 2 /Fio 2,mmHg 260 ( ) 192 ( ) Maximum hematocrit, % 54 (48 61) 55 (47 59) Maximum PTT, s 55 (42 69) 83 (42 186) Minimum platelet count, 10 3 / L 41 (16 70) 63 (14 200) Clinically significant hemorrhage, No Maximum creatinine, mg/dl 1.8 ( ) 1.3 ( ) Maximum LDH, IU/L 1,123 (556 1,609) 1,344 (424 2,300) Maximum AST, IU/L 268 (97 618) 154 (25 405) Maximum ALT, IU/L 134 (60 265) 183 (25 405) Maximum CK, IU/L 580 (98 931) 1,358 (140 3,209) Minimum sodium, meq/l 130 ( ) 121 ( ) *Data are presented as mean (range) unless otherwise indicated. Two-sample Wilcoxon rank-sum (Mann-Whitney) test or Fisher s Exact Test was performed, and p 0.05 was considered statistically significant. 552 Clinical Investigations in Critical Care

6 During the cardiovascular stage, which appeared around the fourth or fifth day after the initial prodromal symptoms, pulmonary edema developed suddenly. On the chest radiographs, pulmonary edema shadows were evident in all patients, but we did not find pleural effusions described as frequently as in the North American patients. 23 Patients in whom massive pulmonary edema developed in 24 h from ICU admission did not survive. The speed of radiologic worsening seems to be a bad prognosis factor, and it was associated with the worsening of Pao 2 /Fio 2 values. Patients who developed refractory shock died in 24 h despite the use of inotropic vasoactive drugs and volume loading. Hemodynamic measurements in five patients receiving inotropic drugs and parenteral fluids showed normal PAOPs and normal or low CI, as described in the North American literature, 6,11 but decreased SVRI in two patients. We did not use extracorporeal membrane oxygenators, a therapeutic approach that seems to be useful, because we did not have these resources. 24,25 One of the major findings of our study is that during the cardiovascular stage of the disease, 81% of the patients had hemorrhage. In 63% of them, hemorrhage was moderate to severe, and most of these patients bled from more than one source. In four patients, hemorrhage was extremely severe and preceded death. In the North American literature, microscopic hematuria and prolonged PTT were described, but severe clinically significant hemorrhage is not mentioned. 6 Hemorrhages were not described in the Argentinian HPS cases. 22 Hyponatremia as a manifestation of the disease was present in 69% of our patients. There was no correlation between hyponatremia and the amount or composition of the administered fluids. Altered renal function test results were seen in 54% of our patients, and two patients showed overt renal failure. No correlation between hyponatremia renal function was found. Renal failure was not described in the first North American HPS patients, 6 11 but high serum creatinine levels were reported in the Argentinian HPS casuistic 22 as well as in some North American HPS patients. 6 The Andes virus seems to trigger a mixed clinical picture between the variants isolated in the North American and the Asian Hantaviruses. Linderholm et al 26 described pulmonary involvement in patients with hemorrhagic epidemic fever. In 1996, HPS with renal failure caused by the Black Creek Canal virus was also described. 13 In the North American patients, hyperamylasemia was seen and attributed to ribavirin. 27 Our patient with hyperamylasemia received neither ribavirin nor amantadine. The global mortality was 43.8%. Patients who died suffered severe hemodynamic compromise and catastrophic respiratory failure, which worsened in 12 to 24 h despite the use of mechanical ventilation and vasoactive drugs. The survivors stabilized their hemodynamic failure and respiratory distress in 24 to 48 h (fifth to sixth day of the initial prodromes) and recovered in the following 4 to 7 days. Five patients received methylprednisolone, all of whom were among the survivors. There is a trend toward lower creatinine and clinical hemorrhage, higher platelet count, but longer PTT in steroidtreated patients, but the small number of patients does not allow us to make conclusions about the utility of steroids in this disease, and further controlled studies are necessary. Person-to-person transmission of HPS was documented in Argentina. 17 However, in the Coihayque, XI region of Chile, the seroprevalence of antibodies against Hantavirus in health-care workers was 3.7%, similar to the general population in that community. 20 We studied 67 health-care workers at the Temuco Hospital in the IX region of Chile who attended an average of four critically ill HPS patients, and none of them showed Hantavirus antibodies. 28 Despite intrafamilial clusters of HPS in Chile, the person-to-person transmission of Hantavirus has not been proven in our country. References 1 Hullinghorst RL, Steer A. Pathology of epidemic hemorrhagic fever. Ann Intern Med 1953; 38: Kessler WH. Gross anatomic features found in 27 autopsies of epidemic hemorrhagic fever. Ann Intern Med 1953; 38: Lukes KJ. The pathology of thirty-nine cases of epidemic hemorrhagic fever. Am J Med 1954; 16: Earle DP. Analysis of sequential physiologic derangements in epidemic hemorrhagic fever. Am J Med 1954; 16: Niklasson B, LeDuc JW. Epidemiology of nephropathia epidemica in Sweden. J Infect Dis 1987; 155: Duchin JS, Koster FT, Peters CJ, et al. Hantavirus pulmonary syndrome: a clinical description of 17 patients with a newly recognized disease. N Engl J Med 1994; 330: Zaki SR, Greer PW, Coffield LM, et al. Hantavirus pulmonary syndrome: pathogenesis of an emerging infectious disease. Am J Pathol 1995; 146: Nolte KB, Feddersen RM, Foucar K, et al. Hantavirus pulmonary syndrome in the United States: a pathological description of a disease caused by a new agent. Hum Pathol 1995; 26: Kahn AS, Ksiazek TG, Peters CJ. Hantavirus pulmonary syndrome. Lancet 1996; 347: Kahn AS, Khabbaz RF, Armstrong LR, et al. Hantavirus pulmonary syndrome: the first 100 US cases. J Infect Dis 1996; 173: Hallin G, Simpson SQ, Crowell RE, et al. Cardiopulmonary manifestations of Hantavirus pulmonary syndrome. Crit Care Med 1996; 24: Nichol ST, Spiropoulu CF, Morzunov S, et al. Genetic identification of a novel Hantavirus associated with an outbreak of acute respiratory illness in the southwestern United States. Science 1993; 262: Khan AS, Gaviria M, Rollin PE, et al. Hantavirus pulmonary CHEST / 120 / 2/ AUGUST,

7 syndrome in Florida: association with the newly identified Black Creek Canal virus. Am J Med 1996; 100: Torrez- Martínez N, Hjelle B. Enzootic of Bayou Hantavirus in rice rats (Oryzomys palustris) in Lancet 1995; 346: Morzunov SP, Feldman H, Spiropoulou CF, et al. A newly recognized virus associated with a fatal case of Hantavirus pulmonary syndrome in Louisiana. J Virol 1995; 69: Ravkov EV, Rollin PE, Ksiazek TG, et al. Genetic and serologic analysis of Black Creek Canal virus and its association with human disease and Sigmodon hispidus infection. Virology 1995; 210: Padula PJ, Edelstein A, Miguel SD, et al. Hantavirus pulmonary syndrome outbreak in Argentina: molecular evidence for person-to-person transmission of Andes virus. Virology 1998; 241: Lopez N, Padula P, Rossi C, et al. Genetic characterization and phylogeny of Andes virus and variants from Argentina and Chile. Virus Res 1997; 50: Toro J, Vega JD, Kahn AS, et al. An outbreak of Hantavirus pulmonary syndrome, Chile Emerg Infect Dis 1998; 4: Chaparro J, Vega J, Terry W, et al. Assessment of person to person transmission of Hantavirus pulmonary syndrome in a Chilean hospital setting. J Hosp Infect 1998; 40: Rossi CA, Ksiazek TG. Enzyme-linked immunosorbent assay (ELISA). In: Lee HW, Calisher CH, Schmaljohn C, eds. Manual of hemorrhagic fever with renal syndrome and Hantavirus pulmonary syndrome: WHO Collaborating Center for Virus Reference and Research (Hantaviruses). Seoul, South Korea: Asian Institute for Life Sciences, 1999; Parisi M, Enria D, Pini N, et al. Detección retrospectiva de infecciones clínicas por hantavirus en la Argentina. Medicina (B Aires) 1996; 56: Bustamante EA, Levy H, Simpson SQ. Pleural fluid characteristics in Hantavirus pulmonary syndrome. Chest 1997; 112: Anderson H, Steimle C, Shapiro M, et al. Extra corporeal life support for adult cardiorespiratory failure. Surgery 1993; 114: Crowley MR, Katz RW, Kessler R, et al. Successful treatment of adults with severe Hantavirus pulmonary syndrome with extra corporeal membrane oxygenation. Crit Care Med 1998; 26: Linderholm M, Sandstrom T, Rinnstrom O, et al. Impairment of pulmonary function in patient with hemorrhagic fever with renal syndrome. Clin Infect Dis 1997; 25: Mertz GJ, Hjelle BL, Bryan RT. Hantavirus infection. Dis Mon 1998; 44: Castillo C, Mardones J, Villagra E. Prevalencia de anticuerpos anti-hantavirus en personal de salud en contacto directo con pacientes portadores del síndrome pulmonar por hantavirus: Temuco 1997 a Rev Med Chile 2000; 128: Clinical Investigations in Critical Care