Hantavirus

From IDWiki

Background

  • Enveloped, single-stranded RNA virus within the order Bunyavirales, family Hantaviridae
  • Acquired by inhalation of contaminated rodent urine or feces, and possibly by bites
    • In North America, it is carried by the deer mouse (most common in NA, transmits Sin Nombre), meadow vole (also present, transmits Prospect Hill), and white-footed mouse (also present, transmits New York); also cotton rat, rice rat, shrew, and mole
  • Essentially worldwide, though New World viruses tend to cause hantavirus pulmonary syndrome and Old World viruses tend to cause hemorrhagic fever with renal syndrome
    • In Canada, no cases have been described east of Manitoba
    • No cases of HPS have been described in Ontario since it became reportable in 2001
    • About 4 or 5 new cases annually from southern rural parts of BC, Alberta, Saskatchewan, and Manitoba
  • Incidence of HPS peaks in summer months (in North America)

Clinical Manifestations

  • Incubation period of 14 days (range 5 to 42 days)

Hemorrhagic Fever With Renal Syndrome (HFRS)

  • Caused by Old World hantaviruses, such as Hantaan, Dobrava, Seoul, Puumala, and other Old World hantaviruses
  • Fever, thrombocytopenia, and AKI caused by acute interstitial nephritis
  • Also headache, abdominal pain, low back pain, dizziness, and blurred vision
  • Can have conjunctival injection and petechiae on upper trunk and soft palate
  • Febrile phase lasts 4 to 7 days of acute, severe illness, followed by hypotensive, oliguric, and polyuric phases
  • Leukocytosis and thrombocytopenia seen on CBC
  • Mortality up to 5%

Hantavirus Pulmonary Syndrome (HPS)

  • Caused by New World hantaviruses such as Sin Nombre, Bayou, and Black Creek Canal
  • Incubation for 2 to 3 weeks
  • Prodromal phase
    • Lasts 2 to 8 days
    • Nonspecific syndrome of fevers, chills, myalgias (including severe myalgias)
    • Continues to develop, with headache, vomiting, weakness, abdominal pain (can be severe), and sometimes diarrhea
    • Typically does not include upper respiratory symptoms, except cough and, in children, pharyngitis
    • Some strains can cause conjunctivitis, facial flushing, and a petechial rash
    • Thrombocytopenia is common, and can see elevated LDH
  • Cardiopulmonary phase
    • Characterized by capillary leak
    • Usually characterized by non-productive cough, with rapid onset of shock, coagulopathy, pulmonary edema (including ARDS), bronchorrhea, and arrhythmias
    • Chest x-ray almost always shows bilateral infiltrates suggestive of ARDS
    • Elevated hematocrit (from third-spacing), leukocytosis, atypical lymphocytes, thrombocytopenia (with severity predicting mortality), prolonged PTT, and mild elevations in AST and LDH
      • Triad of a left shift, lymphoid blasts >10%, and thrombocytopenia, is a helpful diagnostic triad
  • Oliguric and diuretic phases
    • Oliguria can last 3 to 7 days, followed by diuresis of variable duration
    • Creatinine may be elevated, but not as severe as HFRS
  • Convalescent phase
    • Initial recovery can be dramatically fast (over days), but complete recovery can be slow
  • Case fatality rate is about 35%

Differential Diagnosis

Diagnosis

  • Serology usually positive by presentation (both IgM and IgG)
  • PCR or immunohistochemical staining are both possible
  • Viral culture is difficult
  • Of note, it is a biosafety risk group 3 pathogen, which requires special precautions in the lab

HPS Case Definition (CDC)

  • Clinical criteria
    • Fever greater than 38.3°C with prodrome of fever, chills, myalgia, headache, and GI symptoms, with one or more of:
      • Bilateral diffuse interstitial edema
      • Clinical diagnosis of ARDS
      • Unexplained respiratory illness resulting in death where autopsy demonstrates noncardiogenic pulmonary edema
      • Healthcare documentation listing a diagnosis of hantavirus pulmonary syndrome
      • Death certificate listing hantavirus pulmonary syndrome
  • Laboratory criteria requires one of:
    • Reactive IgM, or rising titres of IgG
    • PCR/NAAT
    • Antigen by immunohistochemistry on biopsy
  • A confirmed case requires both clinical and laboratory criteria

Management

  • Supportive