how long has zika virus been around

Posted by exco at 4:47 AM

there are a lot of viruses out there thatcan infect humans, but two things that can get really alarming is when a virus spreadsquickly and when it causes serious harm. zika virus has the potential to do both of thesethings, which is why it’s gotten a lot of attention. given this, it makes sense to understanda bit about zika virus and the disease it causes. zika virus is an arbovirus, meaning it’stransmitted via certain arthropods, specifically mosquitos, so it’s a mosquito-borne virus.mosquito-borne doesn’t mean that the virus is “born” in the mosquito, though, butit’s “borne”, with an ‘e’, which means carried or transported. sometimes wecall organisms like this “vectors”, where

all they do is transport the virus. so withzika virus, just like other mosquito-borne viruses like dengue fever, yellow fever, japaneseencephalitis, and west nile virus, the mosquito acts as a vector that transmits the virusfrom one person to the next. these viruses are all in the genus flavivirus. in order to mature her offspring, female mosquitoesneed a blood-meal, which they get from unsuspecting hosts. mosquitoes find their blood-meals usingchemical compounds that we and other organisms give off, like carbon dioxide, ammonia, lacticacid, and octenol. so when a mosquito that also happens to be carrying the virus findsher meal and digs in, the virus infects the human host and starts to multiply or reproducewithin the human. with most flaviviruses though,

the virus isn’t able to replicate enoughin the human host to actually be able to reinfect another mosquito, and so the human is considereda dead-end-host. however, the zika virus, along with yellow and dengue fever, is wellenough adapted to human hosts such that they can multiply to a point where it can re-infectanother unsuspecting mosquito, which can then go on to infect more people. this window lastsfor the first week of infection, during which the zika virus can be found in the blood.so if humans with the disease can transmit back to mosquitoes then you can imagine thatareas where there’re a lot of mosquitoes, would be a set-up for spreading the virussuper quickly, right? now the zika virus is transmitted via mosquitosin the aedes genus. these blood thirsty little

guys can bite at night, but are mostly activeduring the daytime. aedes mosquitoes are also the same ones that transmit chikungunya feverand dengue fever. when aedes aegypti or aedes albopictus, both species of aedes mosquito,lands on your skin and sticks in it’s long nose—or proboscis, it pierces the epidermiswhich is the topmost layer, composed almost entirely of keratinocytes. keratinocytes basicallyserve to protect against foreign pathogens, and it’s typically pretty good at that.that proboscis though keeps going into the dermis, since the epidermis just gets oxygenfrom the air and doesn’t have its own blood supply, whereas the dermis does, and thisis what our mosquito’s after, right, the blood meal. since the proboscis goes throughboth the epidermal and dermal layers, the

cells in those layers are susceptible to infectionby zika virus. so in addition to keratinocytes, fibroblasts, and dendritic cells have alsobeen found to be permissive to zika virus, meaning they have some sort of receptor orattachment site that basically says, here you go man, come on in. now we still don’t know everything aboutthe zika virus infection, but we do know that when it enters the cell, it injects a single-strandedpositive rna strand. positive means that this piece of rna’s a lot like our own mrna;it’s basically ready to rock and get translated into proteins. the virus’s genome is translatedby our own cellular machinery into more viruses. eventually those cells-turned-virus-making-factoriesdie, which actually ends up releasing more

viruses to infect more cells. as bleak as all that sounds, our immune system’sactually pretty good at fighting off zika virus, and only 1 in 5 get sick from infection,and the often the others won’t even notice they’ve been infected. common symptoms whenpatients have them, are mild fever and skin rash, but some also experience muscle andjoint pain, headaches, and conjunctivitis, or red eyes. the incubation period, or timefrom infection to symptoms isn’t known, but it’s thought to be from a few days toa week. treatment usually just involves treating thesymptoms, things like getting plenty of rest, drinking fluids to prevent dehydration, andtaking medicine like acetaminophen to help

reduce pain and fever. okay so we’ve hit the “spreads quickly”part, which really matters most in places with lots of mosquitoes, but what about the“causes serious harm” part? well, although it causes mild symptoms in adults, there’smore to the story. in october 2015, in areas of brazil where zika virus has been circulatedquite a bit, public health officials noticed a significant increase in babies born withmicrocephaly, which is when a child is born with an abnormally small head and thereforeabnormally small brain size; this has the tendency to cause serious neurological andintellectual deficits, seizures, as well as vision or hearing problems. it was noticedthat there was a huge increase in babies with

microcephaly—up to a 20-fold increase—amongbrazilian states with zika virus outbreak. as of november 2015, the european center fordisease control has stated that it’s plausible the zika virus is able to cause microcephalyin the developing fetus or newborn, as the zika virus can be transmitted from motherto baby during pregnancy or around the time of birth, although it’s not yet known howoften this happens or how exactly the zika virus is linked to microcephaly. in addition to being spread mostly by mosquitobites, and in some cases from mother to child, zika virus has also been reported to spreadthrough both blood transfusions and sexual contact.

currently, there’s no vaccine for zika virus,so it’s highly advised to take precautions when traveling to areas of outbreak, mostlylimiting mosquito bites, so doing things like wearing bug spray all day, or wearing long-sleeveshirts and pants, especially during the day when the aedes mosquitoes are most active.if infected, it’s especially important to avoid mosquitoes to avoid spreading zika virusto others, especially in that first week of symptoms. the world health organization currentlysuggests pregnant women consult their doctor or travel clinic for guidance and recommendations.