Can endemic diseases be acute?
Endemic and chronic/acute are unrelated properties of a disease. Endemic is a description of the frequency of a disease in a population or in an area. Chronic/Acute is a description of the state or course of a disease in an individual. 

For example, influenza is endemic in North America: the frequency goes up and down, there's always a few people who have it, but most people don't. Periodically the influenza virus mutates, and becomes much more successful at infecting people. The frequency of the disease goes way up, and influenza becomes epidemic. However, regardless of whether the disease is endemic or epidemic, the disease processes is usually acute: it comes on suddenly, it gets worse for a few days, and then it get better (or you die).

Malaria in endemic in much of Africa and SE Asia (it's always around), but the disease can be either acute (you have fever, chills, prostration), or chronic (the parasite lives in your body, and you can be a source of the disease, you don't necessarily have obvious symptoms, but may be suffering long term damage.