Hantavirus

Snapshot

• A 36-year-old man presents to an emergency room in Colorado for shortness of breath. He reports that he works as an exterminator and is often exposed to cockroaches, rodents, and mold. He reports having a flu-like cold a week ago with fevers, chills, muscle aches, and fatigue. A few days ago, he started having a nonproductive cough and shortness of breath even without exertion. His past medical history includes hypertension and hyperlipidemia. On physical exam, there are diffuse rales on bilateral lung fields and decreased breath sounds in the bases. Chest radiograph shows centrally-distributed pulmonary infiltrates, bilateral pleural effusions, and blurred pericardiac border. He is admitted for further management. (Hantavirus pulmonary syndrome)

Introduction

• Classification
  • hantavirus
    • an enveloped, segmented, circular, negative-sense RNA zoonotic virus with helical capsid
    • a bunyavirus
    • transmission via inhalation of aerosolized rodent excretions or saliva
    • clinical syndromes
      • hantavirus pulmonary syndrome (HPS)
        • “Sin Nombre” virus is most common cause
      • hemorrhagic fever with renal failure syndrome (HFRS)
• Epidemiology
  • incidence
    • South America
    • Southwest US
  • risk factors
    • residence or travel in rural areas
    • exposure to rodents
• Pathogenesis
  • the virus causes inflammation, increased vascular permeability, and endothelial damage resulting in massive capillary leak syndrome
• Prognosis
  • HPS
    • mortality rate is 30-40%
  • HFRS
• 3-15%

Presentation

• HPS
  • initial flu-like prodrome lasts 3-6 days
    • fevers and chills
    • fatigue, malaise, and myalgias
    • nausea, vomiting, and diarrhea
  • subsequent pulmonary edema and shock
    • nonproductive cough
    • tachypnea
    • hypoxia
    • diffuse rales due to pulmonary edema
• HFRS
  • fever
    • with headaches, chills, blurred vision, and myalgias
  • hemorrhage
    • petechiae in axilla or soft palate
    • subconjunctival hemorrhage
  • renal insufficiency
• oliguria followed by diuresis phase

Imaging

• Chest radiography
  • indication
    • all patients with HPS
  • findings
    • pleural effusions
    • central pulmonary infiltrates
    • pericardiac haziness (shaggy or fuzzy heart sign)
      • characteristic of HPS
• no cardiomegaly

Studies

• Labs
  • detection of viral RNA via reverse transcriptase-polymerase chain reaction (RT-PCR)
  • detection of Hantavirus-specific immunoglobulin M and G with enzyme-linked immunosorbent assay (ELISA)
  • HPS 
    • ↑ creatine kinase
    • ↓ serum albumin level
  • HFRS
    • ↑ BUN and creatinine
    • ↓ C3
    • hematuria
    • proteinuria
• Making the diagnosis
  • based on clinical presentation and laboratory studies
• patients with acute onset respiratory distress and decreased albumin should prompt suspicion of HPS

Differential

• Cardiac pulmonary edema
  • distinguishing factor
    • typically have notable cardiac findings including S3 gallop and cardiomegaly
• Acute respiratory distress syndrome
  • distinguishing factor
• chest radiograph usually shows peripheral infiltrates and less likely to have pleural effusions

Treatment

• Management approach
  • mainstay of treatment is supportive care
• Conservative
  • supportive care
    • indication
      • all patients
    • modalities
      • intravenous hydration
• hemodynamic and respiratory support

Complications

• Acute tubular necrosis