Commissioned study on conducting tests for Zika virus among asymptomatic people returning from the 2016 Olympic Games and Paralympic Games

Abstract

Introduction and Project Objectives:Zika virus (ZIKV) infection may be associated with severe complications, such as congenital micnocephaty and Guillain Barre syndrome in addition to mosquito-borne transmission, ZIKV may be transmitted by sexual and other non-vector-borne routes. However, most patients with ZIKV infection may be asymptomatic. The risk of travel-related ZIKV transmission from asymptomatic persons returning from the 2016 Rio Olympic and Paralympic Games in Brazil to Hong Kong was unknown. In this study, we investigated the prevalence rate of asymptomatic ZIKV infection and persistence of viral shedding in bodily fluids among these returned travellers. Methods: The subjects of this study included asymptomatic travellers who returned from the Rio 2016 Olympic or Paralympic Gomes to Hong Kong and/or their sexual partners, starting on 15 days to 6 months after their return Serum samples were collected from each subject for anti-ZiKV antibody detection ELISA, immunofluorescence test, and viral load study by real time qRT PCR Additionally, end-stream urine and semen (males! were collected from each consenting subject for detection of ZIKV RNA by real time qRT-PCR assays. Results: Between 22-August-2016 and 28-February-2017. a total of 214 subjects (114 males and 100 females) joined the study Their median age svas 34 years. Seven (3.3%) were pregnant. Their median duration of stay in Brazil was 16 days. Eighty seven (40.7%) recalled having been bitten by mosquitoes during their stay. Two hundred and eight (97.2%) participants reported using mosquito repellents consistently during their travel. A total of 209 serum, 201 urine, and 42 semen samples were collected from the subjects. ZIKV RNA was not detected In any of the serum, urine, and semen samples. Sixteen of 209 (7.7%) serum sam pies were vzealcly positive anti -ZIKV a ntibody by immunofluorescent test, none was positive for antl-ZIKV IqM or IgG by ELISA. All 16 of these individuals had received yellow fever vaccination p'ior to scrum collection. which was likely the reason for the weakly positive antibody response detected by immunofluorescence test. Conclusion: The findings in this stucy suggested that the risk of acquiring ZIKV Infection was low if appropriate preventive measures were implemented. Similar studies with more subjects should be considered for other mass gathering events in ZIXV endemic regions to better characterize the risk of acquiring ZIKV infection during these events and the effects of these preventive measures. Public education of Hong Kong residents traveling to ZlKV-endemic areas on these measures continues to be an important means of preventing importation and local dissemination of ZIKV.