Who gets thrush?

Not healthy patients. One of the most common causes of thrush is chronic antibiotic usage. It can occur with a single course of antibiotics but not usually. It also occurs frequtntly in chronically ill and debilitated patients or those who are immuno-compromised. Healthy patients generally do not get thrush.
Steroid inhalers. It's not just immunocompromised patients. People with COPD requiring steroid inhalers can also get it as a result of improperly using a metered dose inhaler and its attachment.
Anyone can. Thrush is present in young babies to the very oldest adults. This is a yeast infection of the lining of the oral cavity. It can happen for no apparent reason or be brought on by medications/drugs, illness and those with poor immunity. Antibiotics often precipitate this as do certain cancers and medications. Usually treated with oral troches, liquids, or orally swallowed pills and some topicals.