Soundbites - More than 150 scientists call for Rio 2016 Olympics to be postponed because of the Zika Virus crisis

The transcript discusses the potential historical natural immunity in human populations that may slow down virus spread. It also highlights the current outbreak's dynamics, noting that despite travel between infected countries, the spread has not been explosive, offering some comfort.

What factors may contribute to the natural immunity of the human population?

In what ways might the natural population's immunity slow down the virus?

How has the travel of people to and from infected countries affected the spread of the virus?

What observations can be made about the spread of the virus so far?

What is the significance of the outbreak not being explosive according to the speaker?