The CDC likes to track disease vectors like influenza and hepatitis, but the concept that immune status determines susceptibility, or the vital role that diet or environmental factors such as sunlight-mediated vitamin D levels play in whether you contract an illness or not, is mostly ignored by them.
It could be argued that the CDC would be far more effective in their mission of "Collaborating to create the expertise, information, and tools that people and communities need to protect their health" if they paid equal attention tracking dietary vectors of disease creation, such as per capita high-fructose corn syrup or happy meal consumption, or environmental chemical exposures, instead of myopically fixating on an outdated, though hugely profitable germ-centered model of disease causation.
Take the Western diet, for instance, which is increasingly the subject of preclinical and clinical investigation as a disease vector disturbingly effective at generating disease within the human body.
Comment: Medical research in the hands of Big Pharma is generally a disaster, but the silver lining here is that they went from trying to prove that smoking kills to showing that it's so healthy, they want to make a pile of money from it.