Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
There are a lot of viruses out there that can infect humans, but two things that can get really alarming is when a virus spreads quickly and when it causes serious harm.
Zika virus has the potential to do both of these things, which is why it’s gotten a lot of attention.
Given this, it makes sense to understand a bit about Zika virus and the disease it causes.
Zika virus is an arbovirus, meaning it’s transmitted 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, but it’s “borne”, with an ‘e’, which means carried or transported.
Sometimes we call organisms like this “vectors”, where all they do is transport the virus.
So with Zika virus, just like other mosquito-borne viruses like dengue fever, yellow fever, Japanese encephalitis, and West Nile virus, the mosquito acts as a vector that transmits the virus from one person to the next.
These viruses are all in the genus flavivirus.
In order to mature her offspring, female mosquitoes need a blood-meal, which they get from unsuspecting hosts.
Mosquitoes find their blood-meals using chemical compounds that we and other organisms give off, like carbon dioxide, ammonia, lactic acid, and octenol.
So when a mosquito that also happens to be carrying the virus finds her meal and digs in, the virus infects the human host and starts to multiply or reproduce within the human.
With most flaviviruses though, the virus isn’t able to replicate enough in the human host to actually be able to reinfect another mosquito, and so the human is considered a dead-end-host.
However, the Zika virus, along with yellow and dengue fever, is well enough adapted to human hosts such that they can multiply to a point where it can re-infect another unsuspecting mosquito, which can then go on to infect more people.
This window lasts for 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 that areas where there’re a lot of mosquitoes, would be a set-up for spreading the virus super quickly, right?
Now the Zika virus is transmitted via mosquitos in the Aedes genus.
These blood thirsty little guys can bite at night, but are mostly active during the daytime.
Aedes mosquitoes are also the same ones that transmit Chikungunya fever and 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 epidermis which is the topmost layer, composed almost entirely of keratinocytes.
Keratinocytes basically serve to protect against foreign pathogens, and it’s typically pretty good at that.