Viruses exist where there is life, it's not a mound I'm willing to die on, but it's accurate here on Earth. There is life that lives in temperatures higher than 70 °C, therefore there are viruses that can survive in temperatures higher than 70 °C: http://www.rcn.montana.edu/Publications/Pdf/2005/4_18Young.p...
There can be some or many kinds of viruses that survive under all sorts of conditions, by that doesn't necessarily imply that a particular virus does so as well.