Zika virus (ZKV) is an arbovirus of the Flaviviridae family, which includes West Nile, dengue fever, yellow fever, and Japanese encephalitis virus. It is transmitted by the Aedes genus of mosquitoes. Before 2015, ZKV outbreaks occurred in areas of Africa, the Pacific Islands, and Southeast Asia. The current large outbreak, which began in Brazil, has also emerged throughout a large part of South/Central America, a number of islands in the Caribbean, including Puerto Rico, the Virgin Islands, and Mexico. A sudden rise in the numbers of infants reported born with microcephaly in Brazil, and the detection of the single-stranded positive RNA virus in the amniotic fluid of affected newborns, has captured medical, mainstream media, and global political attention, causing considerable concern in a post-Ebola global community considerably more focused on the threat of internationally transmissible diseases. The goal of this article is to provide an overview of ZKV for clinicians, with the emphasis on pathogenesis, clinical manifestations, diagnosis, and treatment/preventive measures.
On March 26, 2015, an outbreak of Zika virus (ZKV) transmitted via Aedes mosquitoes was detected in the blood samples of 24 patients in the small town of Bahia, Brazil. Transmission of the virus has spread rapidly to become an emerging epidemic of global concern. The epidemic in Brazil alone is estimated at 440 thousand to 1.3 million cases. The 2013-2014 ZKV outbreak in French Polynesia has been the largest outbreak to date. Experts believe that the virus was introduced into Brazil during the World Cup soccer competition in 2014, during which four Pacific countries (New Caledonia, French Polynesia, Easter Island, and Cook Islands) in which ZKV circulated in 2014 had teams participating in this contest. With more than 2.7 million arrivals from Brazil to the United States (September 2014-August 2015), Bogoch et al listed high-risk international pathways for the dispersion of ZKV and other global destinations with appropriate mosquito populations to allow autochthonous transmission.
Furthermore, an abrupt rise in the number of infants born with microcephaly and the detection of the single-stranded positive RNA virus in the amniotic fluid of affected newborns has produced significant global concern. The goal of this article is to provide an overview of ZKV for clinicians, with emphasis on pathogenesis, clinical manifestations, diagnosis, treatment, and preventive measures.
Pathogenesis
Zika virus is a mosquito-borne flavivirus related to dengue virus, yellow fever virus, and West Nile virus. Zika virus is a single-stranded positive RNA virus (10,794-nt genome), which is closely related to the Spondweni virus and is transmitted by several Aedes mosquitoes, including Aedes africanus, Aedes hensilli, Aedes luteocephalus, and Aedes Aegypti. Zika virus was first recognized in rhesus monkeys in 1947 during the sylvatic yellow fever surveillance in the Zika Forest of Uganda, and reported in humans in 1952 (Figure 1). Of the 2 known lineages of the ZKV (African and Asian), phylogenetic studies indicate that the closest strain of ZKV to that which emerged in Brazil was isolated from samples taken in French Polynesia and spread among the Pacific Islands, and belongs to the Asian lineage.
The literature reports that the human epidermal keratinocytes, dermal fibroblasts, and immature dendritic cells are permissive to the most recent ZKV isolate, responsible for the French Polynesia epidemic.7 The virus next moves to the lymph nodes, where autophagosomes may form, causing enhanced viral replication and viremia.7 The notorious association of the virus and newborn microcephaly remains to be independently confirmed and verified.
To date, ZKV has been reported in human blood as soon as the day of the illness, whereas the viral nucleic acid has been detected until 11 days after onset. Ether, potassium permanganate, and temperatures >140°F (>60°C) have reportedly eliminated ZKV, whereas 10% ethanol has failed to neutralize the virus.
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-Waqas Shuaib, MD, Hashim Stanazai, MD, Ahmad G. Abazid, MD, Ahmed A. Mattar, MD
This article originally appeared in the August 2016 issue of The American Journal of Medicine.
