The Zika epidemic 'vaccinated' half of Latin America, so it won't happen again

In 2015 and 2016, the world was in a panic about Zika. This previously obscure mosquito-borne virus had exploded into an epidemic in Latin America, spreading incredibly quickly.

Zika wasn't, in itself, a very serious infection — it caused no more than mild, flu-like symptoms in most people. But it was terrifying for what it did to babies. Infections in pregnant women led to developmental problems in their infants including microcephaly: incompletely developed brains and skulls.  

• Research paper in the journal Proceedings of the National Academy of Sciences 

But after 2016, the wildfire of Zika infections just seems to have petered out. Zika didn't completely go away, but the explosive spread of the virus did end.  

Dr. Eva Harris from the University of California Berkeley School of Public Health was on the ground in Nicaragua when Zika hit. 

Working with Nicaraguan colleagues, she used an antibody test specific to Zika and determined that in just two to three months in Nicaragua, nearly 50 per cent of the entire population —  56 per cent of adults and 36 per cent of all children — were infected with the virus. 

Since those infected by Zika are immune to furture infection, the population can't ustain a new Zika outbreak since there just aren't enough vulnerable people. It helped scientists explain why after the massive outbreak two years ago, the explosive spread of Zika ended. 

• How Zika mutated and became a terrifying plague 
• Scientists scouring southern Canada for Zika-carrying mosquitos
• Why we're fighting mosquito-borne diseases - with more mosquitoes
• The virus outbreak - from Aedes to Zika