Epidemiological and clinical features of the 2016-2018 Zika virus outbreak in northern Argentina

Background: During the American epidemic, Zika virus (ZIKV) expanded rapidly through dengue virus (DENV)-endemic regions. We analyzed the presentation of ZIKV infection in patients from the City of Oran, Argentina, and compared some of its features with dengue presentation in the same region. Methods: A retrospective study was conducted at San Vicente de Paul Hospital during 2016-2018. Clinical and demographic characteristics, pre-existing immunity to DENV, viral load and type I interferon (IFN) responses were studied in 63 patients with ZIKV infection. Results: Clinical manifestations of ZIKV infection were generally mild compared with dengue, although rash (p<0.001) and itching (p<0.001) were significantly more prevalent in ZIKV patients. ZIKV patients aged <15 y manifested relatively mild disease compared with older ZIKV patients, showing a decreased prevalence of headache (p=0.008), retro-orbital pain (p=0.001) and arthralgia (p=0.001). Increased Zika incidence was observed in female patients (60.3%). Serum viral load was low to undetectable in ZIKV patients and was not associated with serum anti-DENV IgG titers. Interferon-alpha and IFN-beta serum levels did not correlate with serum viral load in ZIKV patients. Conclusions: Clinical presentation of ZIKV and DENV infections is largely overlapping, presenting a challenge for diagnosis and risk assessment for uniquely at-risk populations.