It is variously described as a sense of tiredness, lethargy, irritation, or hangover.
en.wikipedia.org Rare cases of lethargy occasionally progressing to stupor, sometimes with associated hallucinations or convulsions have been reported.
en.wikipedia.org Clinical signs associated with infection are nonspecific and may include appetite loss, uncoordinated swimming, lethargy, coelomic distention, darkening skin color, petechiae, fin erosion, and death.
en.wikipedia.org Initially, the infected patients experience symptoms such as: severe headaches, delirium, lethargy, meningism, bradykinesia, and incoordination.
en.wikipedia.org Symptoms of heatstroke include restlessness, excessive thirst, heavy panting, lethargy, lack of appetite, dark tongue, vomiting, and lack of coordination.
en.wikipedia.org