Big Zika Decline in the Western Hemisphere

[BillTre]

Cases of Zika virus infections (some of which are associated with newborn brain damage) have declined to an unexpected degree in North, South and Central Americas.
For example: local transmission in the US went from 224 last year to 1 this year.

Article above discusses why?

 

[berkeman]

Interesting. I had been wondering why there was such a drop-off. Thanks Bill.

Better control of Zika's vector, the Aedes aegypti mosquito that thrives in the hotter, southern part of the country, doesn't explain the dearth of cases. Nor are other factors such as climate change at work, experts say. Instead, Zika cases have plummeted in Latin America and the Caribbean, where the virus raged over the past 2 years, and much of the population is now immune to it. That, in turn, means fewer infected people entering the United States, reducing the chances of mosquitoes spreading the virus to susceptible people. The respite, experts say, could last for years.

 

[Fervent Freyja]

I know it's weird. It isn't really clear on why the decrease is happening sooner than predicted, the article speculates that the cause was "herd immunity". I couldn't find much else on it.

 

[jim mcnamara]

@Fervent Freyja I am with you. There isn't much to go on. (Guess on my part): Most Zika infections are sub-clinical, so you can have a massive wave of infections that go completely unnoticed and in a few years almost everyone has been exposed and developed antibodies. This has to be the primary working assumption.

I do know: I came back from Peru and tested positive for a lot of diseases and that I have no recollection of enduring any symptoms related to them. Like blinding headaches and possibly paralysis I should have had but did not, from a high elevation encephalitis I tested positive for... my interleukins and their friends were busy killing off something else and clobbered the encephalitis as a side effect. I guess.

 

[SciencewithDrJ]

Dengue virus is also transmitted by the same mosquito (A. aegypti), and serological testing sometimes confuses the two epidemics (due to similarity of the antibodies against the two viruses). Could it perhaps be that Zika cases were just "re-classified"? I can't imagine how this can produce such a massive and widespread reported decline everywhere, though. This could be a good graduate student research project.