I thought you would be interested in the attached information about susceptibility to Zika related to ApoE genotype and the population effects of cryptosporidium resistance, since cryptosporidium is so common in the polluted waters of Brazil and ApoE4 provides a survival advantage against cryptosporidium. Unfortunately ApoE4 also endows susceptibility to inhibition of neurogenesis due to viral infection, observed with HIV and perhaps also occuring with Zika.

I have attached a PDF with much more information and relevant references. There's also some info on the mechanism for inhibition of neurogenesis related to the interactions of ApoE4 with CXCR4 and CCR3, as those two are involved in the antiviral immune response.