We don't know about Zika because it's a fairly benign disease outside of the increased microcephaly risk, which was in turn hidden by the high infant mortality rates in the poor countries it has been active in since forever. Also, it's not some kind of apocalyptic risk: there have been increases in the rates of babies born with microcephaly by over 400 % in areas of Brazil with Zika, true, but we're talking about an increase from 0.6 to 2.8 out of 10.000 live births. From a societal perspective, it's negligible.
And to counter some of the more common misconceptions:
- No, it doesn't stay in you forever. It stays for what looks like a few weeks. After that you are likely immune.
- Current findings suggest no transmission route beyond sexual from male to female and by mosquito bite, and only during the weeks you are a carrier. We also don't know the actual transmission rate, just that it's possible.
- There have been concerns about Zika mosquitoes jumping a plane and spreading to other countries that way, but that could happen anytime. It has nothing directly to do with the Olympic Games.
As always: ignore the media, read what the CDC and WHO say instead.
https://www.cdc.gov/zika/
http://www.who.int/mediacentre/factsheets/zika/en/
You also have a misconception about mutations. Viruses mutate randomly according to their inherent mutation rate, it's not affected by the presence of other pathogens. Also, there's no reason to think that mutation will make it more dangerous. Mutations are random and will lean towards traits over time that make the virus more competitive, yes, but increased virulence is not one such trait. Mutations are also limited to the size and existing traits of the virus: they can't be too drastic because the virus needs the traits it already has. Dramatic changes in behaviour is extremely uncommon because of this, and complete transformations are borderline impossible.
http://www.virology.ws/2016/04/14/zika-virus-like-all-other-viruses-is-mutating/
You want something to freak out about? Check out global antibiotic resistance. Prevailing patterns suggest that we will be unable to treat many dangerous bacterial infections in just a few decades, possible sooner. We're heading back to the times when even healthy people could die suddenly from a small nick or from something that looked like a cold. Now
that's an ongoing and seemingly unstoppable global medical apocalypse in the making.