The very walls of hospitals could become germ-fighting structures. It sounds sci-fi, but paint maker Sherwin-Williams is introducing Paint Shield, a microbicidal paint that kills infection-causing bacteria. The company says it’s the first microbicidal paint to be registered with the US Environmental Protection Agency. Germophobes may clamor for the paint for their homes, but it’s designed for more industrial applications in hospitals, athletic facilities, schools and cruise ships. US-based Sherwin-Williams, which distributes internationally, announced the…