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As the scale of the impact starts to emerge, scientists are scrambling to learn more about the little-known virus. Is it evolving to be more severe and contagious in humans? Or has it taken off so aggressively simply because someone carried it to a new place with the right mosquitoes?
What is worrying virologists, says Paolo Zanotto of the University of Sao Paulo in Brazil, is that before 2000, Zika wasn’t known to spread widely among humans or cause the kind of complications we are seeing today, such as stunted brain development in fetuses and the potentially fatal neural disorder Guillain-Barré syndrome.
It evolved in Africa as an infection of forest animals – possibly primates – that occasionally infected people, but never spread. Decades ago it invaded some parts of South-East Asia, abandoning animals and spreading solely among humans, but went no further.
Now that Asian strain is exploding. “I suspect the virus may have changed,” says Scott Weaver of the University of Texas in Galveston. It may be able to infect mosquitoes more easily, or multiply to higher levels in humans, so a mosquito is more likely to ingest some and infect her next victim.
Read full, original post: Did Zika’s recent mutations let it explode as a global threat?