 A dairy worker in Texas and two in Michigan also had confirmed cases of the virus. About one quarter of Colorado's dairy herds have been quarantined after positive tests for the avian flu since this spring. For NPR News, I'm John Daly. The Caesar salad is celebrating its 100th birthday. Legend has it that an Italian immigrant, Caesar Cardini, invented the dish on July 4, 1924 at his restaurant in Tijuana, Mexico.