As the weather changes people tend to fall under it, often catching colds, sometimes experiencing fever – חום

.

Now, חום

means fever in the conventional sense – it means literally “heat”. But when a fever signals a more serious illness, the better word for it is קדחת

(which means fever in Biblical Hebrew).

Likewise, “feverish” is קדחתני

, as in:

הם עובדים בקצב קדחתני.

They’re working at a feverish pace.