Laboratory findings in Zika infection: The experience of a reference centre in North-West Italy

Background: Zika virus (ZIKV) remains a public health concern due to its association with fetal malformation and neurologic disease. Objective: To report a reference centre experience on ZIKA virus (ZIKV) infection in travelers from epidemic countries from January 1 to September, 30, 2016 in Italy North-West (a geographic area covering 4.424 million inhabitants, corresponding to almost 73% of Italy North-West area). Study design: One hundred and twelve febrile travelers were studied to rule out a tropical fever [e. g. malaria, dengue (DENV), chikungunya (CHIKV), West Nile (WNV) and ZIKV]. Molecular tests for detecting ZIKV RNA were applied on serum or urine as well as IgG and IgM specific serology. Results: ZIKV was the most frequent "tropical infection (11.6%) with 12 infected travelers and one sexual partner of an infected traveler. At the time of the diagnosis, ZIKV RNA was detected in the blood from 9 patients (69%) within 7 days from symptom onset; afterwards, the virus was detected only in urine (5 patients) and ZIKV IgM was reactive in 9 patients (69%). Travelers with ZIKV infection tested negative for DENV, CHIKV, WNV and malaria and completely recovered. Other infections identified in travelers were DENV (5 patients, 4.5%), CHIKV (1, 0.9%), malaria (Plasmodium vivax, 1, 0.9%), measles (1, 0.9%) and tuberculosis (1, 0.9%). Conclusions: The etiologic diagnosis of a febrile illness in travelers where ZIKV is endemic is highly desirable as they are sentinel of a challenging epidemiology including the risk of autochthonous transmission in non endemic countries where the competent or carrier vector is present.