Zika: a realistic view of what we know

“As you’ve probably seen, unless you’ve been living in a cave, Zika virus is the infectious disease topic du jour. From an obscure virus to the newest scare, interest in the virus has skyrocketed just in the past few weeks:   I have a few pieces already on Zika, so I won’t repeat myself here.…”

Sourced through Scoop.it from: scienceblogs.com

Nice, cautious piece by Tara Smith.  I have been trying, via Twitter, to damp some of the hysteria and hype about Zika – but who cares about one cautious voice?  So there should be MORE – and this is one such.

Zika virus is a flavirirus related to dengue and yellow fever and Japanese encephalitis and West Nile viruses, and like them, is mosquito-transmitted.  In fact, it is transmitted by the same “yellow fever mosquito” – Aedes aegypti – as transmits YFV and dengue, and like them, has been spread around the tropics of the planet along with the mosquito vector.

The mosquito is an interesting beast, because it is hardy, can breed in very small deposits of water, such as are found in urban areas in flower vases, uncovered barrels, buckets and such, likes preying on humans, and flies during the day – unlike most of its relatives.  It also has a penchant for breeding in places like discarded car tyres, and it turns out that a LOT of these are literally shipped around the developing world from developed countries like Japan and the USA, which has resulted in the mosquito going worldwide from its African origins.

The Zika virus is nothing like as nasty as dengue or YFV or JEV: there are apparently no deaths of children or adults that can be attributed to infection with it, unlike the case with its relatives.  Where it is potentially dangerous is the apparent linkage – in naive populations – with microcephaly, and also a stronger link with the paralytic Guillain-Barre syndrome.

I stress “in naive populations”: the virus was discovered in Uganda’s Zika Forest in 1947, and is endemic over large swathes of tropical Africa, where it is not associated with anything other than mild and often inapparent infections, easily confused with influenza.  Its endemicity also means that literally everyone that can be infected will have been AS A CHILD – and presuming that like YFV, exposure leads to lifelong immunity, adults will be immune to the virus AND the purported side effects.  It is interesting that the African subspecies of A aegypti – which has apparently NOT left Africa – does not like to bite humans and is probably a less efficient vector.

What will probably happen in Brazil and the South, Central and North American countries that it has spread to or is in the process of doing so, is that it will become endemic there – especially if it adapts to being spread by other mosquitoes such as the much more common Culex spp., which may have already happened.  When that happens, the African experience will become the norm – and hopefully the hype and hysteria will die away.

Until then – well, a vaccine would be nice!  It may help that one of the best characterised and safest attenuated vaccines known is the 17D strain of the genetically similar yellow fever virus – and that unlike dengue, there are no distinct or non-cross-protecting strains or types of Zika virus, meaning only one vaccine should be necessary. And a simple thing to do would be to replace one or both of the membrane proteins of 17D with the Zika equivalents.  Remember who told you…B-)

See on Scoop.itVirology News

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