Zika: from Mild to Wild

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What is Zika?

Zika is a virus that’s recently been hitting the news, due to its nasty effects on new-borns.

The virus spreads via Aedes mosquitos, the species of mosquito that also transmits tropical diseases like yellow fever and dengue. In addition to mosquito-bites, there have been cases of sexual transmission, transmission through blood donation and there is new evidence implying that Zika can pass from mother to baby during pregnancy.

Zika was first observed in monkeys in Uganda in 1947, and remained confined to small African and Asian areas for years without causing trouble. Outbreaks began to occur in 2007 in the Yap islands, 2013 in French Polynesia and finally in 2015 in Brazil. By February 2016 the virus had spread to thirty South American countries as well as parts of central America, the Caribbean and the Pacific.

But before you start to worry, the virus can’t spread to the UK. Travellers can of course bring the virus back, but if they wait six months before having unprotected sex (which we all know is risky business regardless of having Zika or not) then it’s not going to spread anywhere. Luckily, our not-so-lovely weather is too cold for the mosquitoes.

Zika was first observed in monkeys in Uganda

If you do happen to be infected with the Zika virus, you may start to feel some mild symptoms about three to twelve days after you’re bitten. Some of those infected experience no symptoms at all, whilst others might experience a fever, muscle pains, rash, headache, pink eye and will generally feel a bit unwell.

Because the infection usually only results in a mild illness, the treatment for Zika is only supportive- relieving symptoms and trying to keep the person well. There currently isn’t any anti-viral medication against the Zika virus, although there are some vaccines in development.

So what’s the problem?

So far we’ve established that Zika is a mosquito-borne virus that infected lots of people in South America and a few other areas, giving those infected about a week of mild-illness symptoms.

Doesn’t seem like a big deal does it?

The problems all come from the complications of Zika- secondary problems that result from the virus. The complications are what makes Zika so scary and explains why such a previously-ignored disease is only now hitting the headlines, despite being known about for decades.

During the French-Polynesian and the Brazil outbreak there was a much higher incidence of Guillian-Barré syndrome, a condition that causes numbness, weakness and pain in your nerves. Consequently, in severe cases patients have difficulty swallowing, walking and speaking. Other scary complications include meningitis and meningoencephalitis, which cause swelling of the brain’s lining and the brain itself. As you can imagine, both are highly dangerous.

The problems all come from the complications of Zika – secondary problems that result from the virus

Scientists can’t say for definite that the Zika virus itself causes these increases in complications. Other factors may have been involved in the increasing incidence, and it’s extremely difficult to prove that the virus was the singular causative factor or whether external factors played a role. All we can do is acknowledge that during the outbreaks, there were simultaneous peaks in other serious conditions.

The big news about Zika is that it is thought to have caused microcephaly in thousands of Brazilian new-borns. Microcephaly is a condition where a baby’s brain doesn’t develop properly and consequently they are born with a really small head. Depending on how severe the microcephaly is, a baby can face multiple problems such as learning disabilities, problems with vision and hearing, seizures or even death. At the same time as the 2015 Brazil outbreak, there were twenty times more babies born with microcephaly than before. This was not only devastating for the many children and parents affected but caused Brazil to declare a public health emergency as the thousands of affected children struggled to access care.

The latest discovery

Scientists have been working relentlessly to try and work out if and why the Zika virus causes microcephaly in new-borns. A recent article in Science describes the discovery of a genetic mutation that can cause microcephaly in mice, and may explain why Zika suddenly began causing us trouble.

Scientists began comparing the new Zika strain from Brazil to older Zika strains to see what had changed. The protein ‘prM’ inside the virus is what allows Zika to grow in and escape the cells that they’ve infected. It was this protein that the scientists modified inside of the older viruses, before injecting the virus the brains of mice and observing the effects.

one tiny change could have been enough to make the previously harmless virus into the devastating pathogen it is today.

One singular amino acid change was found to cause microcephaly in mice. To put this in context, a single protein is made up twenty amino acids, and swapping just one of these was enough to cause such a devastating pathology in mice. Even though researchers state it is likely that other factors influenced the virus’ pathogenesis, for now, we could speculate that this one tiny change could have been enough to make the previously harmless virus into the devastating pathogen it is today.

So much work went into this research, with twenty-three co-authors on the published paper. This work is important for the future- as scientists now have a specific pathology to target for interventions, notably vaccines. There are currently five or six vaccines being worked on, so hopefully this could eradicate the possibility of a new outbreak, and more devastation.

 

For more on the Zika virus, check out this article written over a year ago, when the Zika virus outbreak was at its worst!