zika virus

introduction

a rapidly emerging mosquito borne infection of the tropics caused by the zika virus, a flavivirus.
like dengue fever, it is spread by Aedes aegypti, but in addition, by Aedes africanus, Aedes apicoargenteus, Aedes furcifer, Aedes luteocephalus and Aedes vitattus
in 2015, it caused major alarm in Brazil where it had spread to in May 2015, and is thought to be the cause of more than 2,400 suspected cases of neonatal microcephaly and 29 deaths of infants that occurred in 2015 compared to only 147 cases of microcephaly in 2014.
- the zika virus enters cells via the AXL receptor and these are found on special fetal neuronal cells called outer radial glia cells as well as astrocytes which are then vulnerable to cell death during zika infections in utero and which then results in impaired brain development and microcephaly. Each outer radial glia cell in human fetuses normally generate 700-1000 upper and lower layer neurons, thus loss of these cells could be expected to dramatically impact brain size. ¹⁾

1st discovered in forest monkeys in Zika Forest of Uganda, Africa in 1947
virus 1st detected in a human in 1968 in Nigeria although human cases occurred in Africa at least from 1951
in 2007, it spread outside of Africa and infected nearly three-quarters of Yap Island's 11,000 residents in Micronesia
in 2013, Zika showed up in Tahiti and other parts of French Polynesia and was responsible for making an estimated 28,000 people so ill they sought medical care
arrived in Brazil in May 2015
in Dec 2015, cases developed in West African nation of Cape Verde and in Panama and Honduras
in Jan 2016, major public warnings for much of America except Canada and Chile as the virus rapidly spreads through 23 countries and expected to infect millions

a flavivirus
enveloped and icosahedral with a non-segmented, single-stranded, positive sense RNA genome
extrinsic incubation period in mosquitoes ~ 10 days
vertebrate hosts: monkeys, humans

usually causes a brief, mild febrile illness with mild headache, maculopapular rash, malaise, conjunctivitis and arthralgia
fever usually resolves within 3 days
appears to cause microcephaly in newborn of infected pregnant mothers

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