Neuroinvasive West Nile virus has become more prevalent in the U.S. in recent years. It typically occurs in July through September, which is consistent with this patient’s labor day weekend presentation. The neuroinvasive form occurs in <1% of people infected with West Nile disease via mosquito bite. This patient’s presentation fits the usual clinical course of neuroinvasive West Nile. Patients often have encephalitis and myalgia for at least 24 hours. Then, there is marked acute flaccid paralysis over 48 hours, similar in character to poliomyelitis with areflexia or hyporeflexia without sensory abnormalities. The findings are usually asymmetric. Prevention includes using mosquito netting in endemic areas. Unfortunately, there is not currently a prophylactic vaccine for this condition.

Diagnosis is confirmed by the detection of West Nile virus-specific IgM antibody in cerebrospinal fluid or serum.

Lyme meningoencephalitis can be prevented with frequent skin exams, but this disorder does not present so acutely as this patient, and the progressive flaccid paralysis is not consistent with Lyme. The CSF profile does not match a bacterial process.