The idiomatic expression "to get the disease" means to contract or acquire a particular illness. It is often used in medical contexts, where it refers to becoming infected with a specific pathogen that causes a certain sickness.
Sentences with «to get the disease»
Is human aging your risk of getting the diseases of aging? (discovermagazine.com)
What should I do to prevent my cats from getting the disease in the first place? (tampabayvets.net)
In contrast, 98 percent of those with a higher high frequency value did not get the disease. (pennstatehealthnews.org)