This study will evaluate the safety, tolerability, and immunogenicity of SAB-301, a fully human polyclonal anti-MERS IgG collected from transchromosomic cattle. Beginning with a low single-dose, subjects are randomized to receive either SAB-301 or a normal saline control, and evaluated on Study Days 1, 3, 7, 21, 42, and 90. The safety and tolerability is evaluated using symptoms, clinical laboratory tests, pharmacokinetics, and immunogenicity assays. Utilizing a series of stopping rules and a medical monitor, the dose will be escalated as safety and tolerability are established.