As of 2007, fewer than 500 Yakut individuals have been infected with VE.<unk>  is classified as a progressive neurological disorder that ultimately ends in the death of the infected individual. The disease has three distinguishable phases: The acute form, the progressive form, and the chronic form. The acute form is the most rapid and most violent of all the stages. It begins with the characteristic rigidity of the muscles, accompanied by slurred speech, severe headaches, and exaggeration of cold-like symptoms. Patients usually die within weeks of the initial symptoms. Routine post-mortem examinations yield: severe inflammation of the brain lining, clusters of dead cells and tissue, and largely increased amounts of macrophages and lymphocytes. The progressive form is the most common case. Patients initially experience acute-like symptoms which are not as severe, and subside within a few weeks. Following the sub-acute phase, the patients experience a few mild symptoms including some behavioral changes, incoordination, and difficulty in speech. Eventually the disease developed fully and those infected were stricken with the characteristic symptoms of rigidity, slurred speech, and deterioration of cognitive functions. Ultimately, brain function depreciates rapidly resulting in death. Many patients who undergo the chronic form claim never to have had an acute attack. These patients endure varying measures of impairment and suffer mental deterioration for the remainder of their lives. Usually they live to be very old and succumb to other diseases. In almost all cases there are changes characteristic of VE. Early onset shows an increased number of lymphocytes and increased protein concentration — which reduces over many years. These factors help neurologists determine the form of VE based on progression. The trademark changes in the brain include: thickened inflamed meninges, necrotic cortical lesions, increased number of lymphocytes, and neuronal death.
Viliuisk encephalomyelitis
Powassan encephalitis
Saint Louis encephalitis
Bickerstaff brainstem encephalitis
La Crosse encephalitis
Acute disseminated encephalomyelitis
Anti-NMDA receptor encephalitis
Eastern equine encephalitis