A 52-year-old man presents with a severe headache and widespread rash after a camping trip. What's your diagnosis?
A 52-year-old man has just returned from an end-of-summer camping trip in Vermont. Two weeks prior to the trip he visited with his doctor complaining of a severe headache in the front of his head and a widespread rash that indicated blanching macules. The headache and rash were evident a few days prior to the office visit, but at that time, it was limited to a mild fever, myalgias, and some loss of appetite.
What's your diagnosis?
A. West Nile virus?
B. Dengue fever
D. Viral exanthem
Click on the next page for the answer.
The correct answer is A: West Nile virus
West Nile virus (WNV) is caused by infection with a flavivirus. The vector of transmission is the Culex, Aedes, and Mansonia mosquitoes as well as some ticks with birds as intermediate hosts.
The virus is endemic in several temperate climates around the world including North America, Europe, Africa, and Australia. Most cases in these regions occur during the late summer and fall.
Most cases are asymptomatic. Patients usually present with mild illness of fever, myalgias, and an associated macular and papular rash on the upper body. Occasionally, an associated hepatitis or encephalitis can be life threatening. The incubation period is typically 3-14 days. Fever and severe frontal headache, backache, and anorexia may precede the central nervous system (CNS) signs and symptoms of encephalitis (confusion, neck stiffness, cranial nerve palsies, and generalized weakness), for which the mortality rate is 40%. Mild illnesses usually resolve in less than 1 week, but prolonged fatigue is common. Symptoms of encephalitis may persist for weeks or may be permanent.
ICD10CM: A92.30 – West Nile virus infection, unspecified
SNOMEDCT: 57311007 – West Nile virus
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