"For the last three months, the dengue outbreak has put southern states on high alert and has been keeping local administration and the health department on their toes."

The sentence is talking about the impact of a dengue outbreak on the southern states, and how it has affected the local administration and health department. The first blank requires a word that describes the dengue situation in the southern states. "Outbreak" is the best choice here, as it refers to a sudden increase in cases of a disease in a particular area.

The second blank requires a word that describes how the local administration and health department have been affected by the outbreak. "Toes" is the best choice here, as it refers to being on alert or being prepared for something, especially in a situation that requires quick action. The phrase "on their toes" suggests that the local administration and health department have been very busy dealing with the dengue outbreak and taking necessary measures to control it.