The phrase "second wave" refers to a new surge or outbreak of something, usually a disease or infection. It suggests that after a period of decline or control, the problem is coming back and spreading again. Full definition
I expect not even about the «surprising» second wave of credit distress that we can expect as we move into 2010. (hussmanfunds.com)
American second wave feminism at this time often had limited sympathy for the struggles faced by women of colour. (aestheticamagazine.com)
Both the first and second waves started in the late 1990s, but the pioneering second - wave cities typically took a decade or more to reach No Kill. (outthefrontdoor.com)