disease with a rapid onset and/or a short course
In medicine, an acute disease or condition either happens for a short time, as in acute infection, or doesn't last long. The word acute may often be confused by the general public to mean 'severe'. This is different: something can be acute but not severe.
The word acute is in the name of many diseases, for example, severe acute respiratory syndrome or acute leukemia.
Acute hospitals are hospitals which are meant for short-term medical and/or surgical treatment and care. The related medical speciality is called acute medicine.
Subacute is described as between acute and chronic. An example is subacute fever symptoms or subacute endocarditis.