LaCrosse Encephalitis Map

LaCrosse Encephalitis Facts & Information:

CLINICAL FEATURES:

  • Frank encephalitis progressing to seizures, coma; majority of infections are subclinical or result in mild illness

ETIOLOGIC AGENT :

  • La Crosse virus - California serogroup virus in the family Bunyaviridae

INCIDENCE:

  • Approximately 70 cases reported per year

SEQUELAE:

  • Case-fatality ratio <1%
  • Hospitalization for CNS infection
  • Neurological sequelae that resolve within several years

COSTS:

  • Short-term hospitalization to long-term care exceeding $450,000
  • Social costs from adverse effects on IQ and school performance

TRANSMISSION:

  • Virus cycles in woodland habitats between the treehole mosquito (Aedes triseriatus) and vertebrate hosts (chipmunks, squirrels)
  • Virus survives winter in mosquito
  • Vector uses artificial containers (tires, buckets, etc.) in addition to treeholes

RISK GROUPS:

  • Children <16 years old: biological risk factor
  • Residence in woodland habitats environmental risk factor
  • Containers at residence environmental risk factor
  • Outdoor activities: behavioral risk factor

SURVEILLANCE:

  • Active case surveillance in collaboration with state and local health departments, and mosquito control districts

TRENDS:

  • Traditional endemic foci in the great-Lakes states
  • Increased case incidence in mid-Atlantic states
  • Rural poor most affected

CHALLENGES:

  • Multiple environmental, biological and social factors contributing to disease occurrence
  • Disease is considerably under-reported
  • No vaccine available