I really don't think so. But then, who knows, a lot of crazy things has been done in the past.
Government conspiracies are like a norm in the society, I think people are just obsessed with bringing up different theories everyday. Given the role the U.S plays as a world police and their goals of achieving ultimate power over everyone, it's only expected that theories of this nature always be associated with their government.
I've heard of so many different conspiracies always related to the U.S government. To be honest with you, I kind of want to believe some, especially those compelling theories that got documented with a little bit of evidence. You can find a lot of them over the internet.
Living dead won't be an easy one even if they wanted too. It involves reanimating the dead, a process which at this time remains an impossible strive for man. Movies make it look easy, but the opposite is the case in reality. The closest man has gotten to bringing the dead back to life, is a secret long gone with Victor Frankenstein. The scientist who is believed to have put together body parts of different daed people and giving it life in a unorthodox scientific experiment.
Let me add a final thought to this answer. Have you heard of the one which says Ebola and SARS was started by the world powers as a means of controlling under developed regions and also cutting down the population, but was immediately intercepted and stopped when the infection began spreading out of proportion and threatening to crossover to their own regions. This sounds similar to your question.