You can try this sample size calculator there : http://www.raosoft.com/samplesize.html
With a population of 5 million, an margin of error of 5% and confidence level of 95% the minimum sample size would be 385. Surveys typically target 3% of margin of error, which would bring the minimum sample size to 1067.
So yeah, this sample is way too small to be used as a headline like this.
Neat tool. Thanks for the link!