Zika Virus

ZIKA VIRUS- BACKGROUND INFORMATION

ZIKV is closely related to other mosquito-borne flaviviruses such as Dengue, Japanese encephalitis, yellow fever, and West Nile. Structurally, like other flaviviruses, ZIKV is icosahedral shaped and enveloped with a non-segmented, single-stranded, positive-sense RNA genome which encodes seven nonstructural proteins and three structural proteins. The structural proteins encapsulate the virus and the replicated RNA strand is held within a nucleocapsid which is contained within a host-derived membrane modified with two viral glycoproteins. There are two lineages of Zika (African and Asian lineage) and phylogenetic studies indicate that the virus spreading in the Americas is 89% identical to African genotypes, but is most closely related to the Asian strain that circulated in French Polynesia during the 2013–2014 outbreak. ZIKV is primarily transmitted by infected Aedes species mosquitos ( A. aegypti and A. albopictus ) although it appears that it can also be spread through blood transfusion and sexual contact. Control measures aim to minimize any exposure to potentially ZIKV infected mosquitos. However, given that the global distribution of A. aegypti is expanding due to global trade and travel (including continents such as North America and the European periphery) ZIKV will likely continue to spread to new areas. Before the current pandemic began, ZIKV was not known to spread widely among humans or cause any neurological complications however ZIKV does possess the ability to mutate rapidly. Sequence analysis has shown that that virus has undergone significant genetic changes in the past 70 years, including substantial DNA changes between the Asian and African lineages, as well as the human and mosquito strains. It has been suggested that these mutations could enable the viruses to replicate more efficiently, evade the body’s immune response or invade new tissues that provide a safe harbor for it to spread. Zika (ZIKV) virus is a mosquito-borne flavivirus that was first identified in a monkey in Uganda in 1947. Outbreaks of ZIKV disease have been recorded in Africa, the Americas, Asia and the Pacific, however, ZIKV appeared in Brazil for the first time in May 2015 and since then has been estimated to have infected up to 1.3 million people and spread to 25 countries and territories. There is scientific consensus that Zika virus is a cause of microcephaly and Guillain-Barré syndrome. Links to other neurological complications are also being investigated.

In general, infection with Zika fever is a mild disease only causing a rash, fever, joint pain, and malaise, similar to Dengue fever. However, ZIKV infection during pregnancy can cause a serious birth defect called microcephaly, as well as other severe fetal brain defects. It has also been linked to other cases of several neurological complications including Guillain-Barré syndrome and hearing difficulties.

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01/23