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Zika virus (ZIKV) is a RNA virus of the Flaviviridae family, genus Flavivirus, which includes other well-known arboviruses such as West Nile virus (WNV), dengue virus (DENV) and yellow fever virus (YFV), the latter two also transmitted by Aedes mosquitoes.

More than half of the world’s human population lives in areas infested with Aedes; consequently, large urban epidemics of Zika, dengue, chikungunya, and even yellow fever have been expected for decades.

Although ZIKV was isolated from a rhesus monkey in the Zika forest of Uganda in 1947, the virus was largely ignored until 2007 when it caused an epidemic on the island of Yap in Micronesia and Gabon[1] followed by an outbreak in French Polynesia during 2013[2]. Deleterious consequences of these epidemics were not noticed in those countries, possibly due to the low population density. However, in early 2015, when ZIKV epidemics hit the northeast region of Brazil, a populous country infested by both Aedes aegypti and A. albopictus, the epidemic showed its true colors. The apparently mild acute infection was associated with serious consequences, such as the increase in the number of cases of Guillain-Barre (already seen after the French Polynesia epidemic) and microcephaly, in ZIKV epidemic regions.

Although not yet proven, a causal relationship between Zika infection during pregnancy and microcephaly is strongly suggested[3]. Meanwhile, reports of sexual and blood transmitted ZIKV infections have increased the controversy associated with the epidemic[4],[5].

So far, no cases of Zika virus have been reported in transplant recipients. Transmission by solid organ or marrow transplantation is theoretically possible since the virus can be transmitted through blood transfusion. It is not known if the disease is more or less severe in the immunocompromised patient. Therefore, it is important for the transplant community to be aware of the risk of ZIKV infections.

Infection with ZIKV is asymptomatic in most people. In symptomatic patients, fever, rash, conjunctivitis, or joint pain are the most common symptoms. Myalgia, asthenia and headache can also occur. The incubation period varies from a few days to a week, and symptoms typically resolve within a week. Severe disease and/or death appear to be very rare in the immunocompetent population. There is currently no vaccine and no treatment for Zika infection. Management of immunosuppressive drugs may be helpful to avoid severe symptoms and lymphopenia. However, the level of evidence for this recommendation is low.

Clinical presentation may help in the differential diagnosis in case of co-circulation of DENV and Chikungunya (CHKV). The main signs and symptoms observed in infections caused by ZIKV, DENV and CHKV are shown in the table below.



Clarisse M. Machado, M.D.
Head of the Virology Laboratory,
Institute of Tropical Medicine
University of São Paulo, Brazil
President-Elect of the TID section

Phone: 1.514.874.1717
- 1.514.874.1716
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Transplant Infectious Disease Section (TID)
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