ACDAugust 8th, 2014

Team 3A

West Nile Virus

• Member of the Japanese encephalitis virus antigenic complex.

• Most people infected with the disease are asymptomatic.

• Only about 20 to 40% of patients manifest any symptoms.

• Typical incubation period is between 2 and 14 days.

West Nile Virus

• Once recovered from disease, immunity is thought to be life-long.

• Usual presentation is a self limited illness characterized by fever, headache, malaise, back pain, myalgias, and anorexia usually lasting 3 to 6 days.

• Eye pain, pharyngitis, nausea, vomiting, diarrhea, and abdominal pain can also occur, but are less common.

West Nile Virus

• Rash occurs in about 25% of patients and occurs less often in patients with neuroinvasive disease.

• This is typically maculopapular and involves the chest, back, and arms

Neuroinvasive Disease

• West Nile can present as encephalitis, meningitis, or flaccid paralysis.

• Encephalitis can range from a mild self limited confusion to severe encephalopathy, coma, and death.

• Cranial nerve palsies can also occur and present with facial weakness, vertigo, dysarthria, dysphagia, or diplopia.

Lab Findings and Imaging

• WBC is usually normal or elevated• In patients with signs of CNS involvement, CSF

usually has lymph predominant pleocytosis and increased protein.

• IgM antibody or viral nucleic acid testing positive

• CT head is almost always normal (don’t waste your time)

• MRI can show signal intensity abnormalities.

Differential Diagnosis

• Tick born illnesses, St. Louis Encephalitis, Eastern Equine, HSV, and Enterovirus should all be on the differential.

• Bacterial causes should also be ruled out.

Treatment

• Supportive care• Some reports of using interferon, ribavirin,

and IVIG. There is not much data to support this.

References

• Uptodate.com• MKSAP16 Infectious Disease