Zika Virus and Guillain-Barré Syndrome Association

Zika virus is a single-stranded RNA flavivirus first isolated in 1947 in Zika Forest, Uganda. Major transmission via Aedes aegypti and Aedes albopictus mosquitoes, with secondary modes including sexual transmission (semen carries virus for months), vertical/transplacental transmission causing congenital Zika syndrome, blood transfusion, perinatal, and laboratory exposure. The 2015-2016 outbreak in Americas demonstrated previously unrecognized neurological complications including congenital microcephaly and Guillain-Barré syndrome (GBS). Zika-associated GBS observed in French Polynesia outbreak 2013-2014 (24-fold increased incidence), Brazil 2015-2016, Colombia, Venezuela, and other affected countries with consistent 1.2-2.6/10,000 Zika cases developing GBS.

Pathophysiology of Zika-associated GBS: molecular mimicry between Zika viral antigens and peripheral nerve gangliosides (GD1a, GA1, GD3, GT1a) leads to autoantibody-mediated nerve damage. Several GBS subtypes observed: acute inflammatory demyelinating polyradiculoneuropathy (AIDP — most common Western form), acute motor axonal neuropathy (AMAN — predominantly motor), acute motor sensory axonal neuropathy (AMSAN), Miller Fisher variant (ophthalmoplegia, ataxia, areflexia). Zika-GBS shows shorter incubation (median 6-10 days vs 1-3 weeks for typical GBS), more rapid progression, more facial involvement, possibly more axonal involvement with worse prognosis. Clinical course: post-Zika illness onset 1-3 weeks after acute infection (which may be subclinical), classical ascending weakness from feet upward, decreased reflexes, sensory symptoms (paresthesias, pain), autonomic dysfunction (dysrhythmias, blood pressure lability), bulbar symptoms, respiratory failure in 25-30% requiring mechanical ventilation, peak weakness within 4 weeks then plateau and recovery.

Diagnosis is by clinical features (ascending paralysis, areflexia, history of antecedent illness), CSF showing albuminocytologic dissociation (elevated protein with normal cell count, present in 60-90% by 2 weeks), nerve conduction studies showing demyelinating or axonal pattern, exclusion of mimics (acute disseminated encephalomyelitis, transverse myelitis, botulism, myasthenia gravis), Zika confirmation via RT-PCR (blood within 7 days of symptoms, urine within 14 days, semen, CSF), serology (Zika IgM by ELISA — cross-reacts with dengue requiring plaque reduction neutralization test PRNT), antibodies against gangliosides. Treatment: intravenous immunoglobulin (IVIG) 0.4 g/kg/day for 5 days as first-line, plasmapheresis (5-7 sessions) as alternative — both reduce duration and severity but do not affect mortality; supportive care critical with respiratory monitoring (forced vital capacity, negative inspiratory force), mechanical ventilation if FVC <15 ml/kg or rapid deterioration, autonomic monitoring, DVT prophylaxis, nutritional support, pain management, physical therapy. Prognosis: 80-85% recover but 20% have residual deficits at 1 year, mortality 3-5% (respiratory failure, cardiac arrhythmias, infection). Prevention via mosquito control, travel advisories for pregnant women, sexual transmission prevention, no specific antiviral or vaccine for Zika.