Introduction: Zika virus (ZIKV) has generated global interest in the last five years mostly due to its resurgence in the Americas between 2015 and 2016. It was previously thought to be a self-limiting infection causing febrile illness in less than one quarter of those infected. However, a rise in birth defects amongst children born to infected pregnant women, as well as increases in neurological manifestations in adults has been demonstrated. The objective of this study was to systemically review the literature to understand clinical manifestations and health outcomes in adults globally.
Methods: A systematic review was conducted by searching MEDLINE, Embase, PubMed, CINAHL, LILACS, and WHO's ICTRP clinical trials registries database using terms related to “Zika virus” and “Zika infection” from inception until December 2018. Two independent reviewers conducted screening and data extraction for primary studies reporting outcomes (clinical signs/symptoms and complications) of ZIKV infection in adults. Conflicts were resolved by consensus or a third reviewer. Joanna Briggs Institute checklists were used for quality appraisal.
Results: We identified 53 studies globally that reported clinical outcomes in ZIKV-infected adults, of which 40 studies were from the Americas. From studies that met 70% of critical appraisal criteria and among subjects with confirmed ZIKV, the most common symptoms included: exanthema (2,702/3,134; 86%), fever (1,920/3,129; 61%), arthralgia (1,886/3,129; 60%), conjunctivitis (1,211/3,085; 39%), myalgia (473/1,993; 24%), headache (499/2,212; 23%), and diarrhea (95/425; 22%). Six percent of infected cases developed neurologic sequelae, of which 89% were Guillain-Barré Syndrome (GBS). Most subjects reported recovery from peak of neurological complications, though a small proportion endured chronic disability. Mortality was rare (0.4%) and hospitalization (16%) was often associated with co-morbidities or GBS.
Conclusions: The ZIKV literature in adults was predominantly from the Americas. The most common systemic symptoms were exanthema, fever, arthralgia, and conjunctivitis; GBS was the most prevalent neurological complication. Future ZIKV studies are warranted with standardization of testing and case definitions, consistent co-infection testing, reporting of laboratory abnormalities, and separation of adult and pediatric outcomes, and assessing for causation between ZIKV and neurological sequelae.