California virus encephalitis

This diagnosis code identifies encephalitis caused by the California serogroup of bunyaviruses, which are typically transmitted by mosquitoes. It represents an acute inflammation of the brain parenchyma resulting from infection with viruses such as La Crosse encephalitis virus.

Assign this code when documentation explicitly states a diagnosis of encephalitis due to a California serogroup virus. This typically follows laboratory confirmation of the specific viral etiology, such as positive serology or PCR for La Crosse virus.

• Ensure documentation specifies "California virus" or a specific virus within that serogroup (e.g., La Crosse virus) as the causative agent.
• Do not use for encephalitis of unspecified viral origin; a more general code would be appropriate in such cases.
• Consider sequencing this code as the primary diagnosis if it is the main reason for the encounter and treatment.