McSweegan has commented on diverse issues related to infectious disease. In 2004, McSweegan hypothesized that the mysterious "English sweating sickness" may have been an outbreak of anthrax poisoning. He speculated that the victims could have been infected with anthrax spores present in raw wool or infected animal carcasses, and he suggested exhuming the victims for testing. He has also criticized the Centers for Disease Control for investigating Morgellons, a proposed infectious condition whose existence is disputed by current scientific consensus.