The conjunction should be "or" not "and"; and the lack of Oxford comma really, really hurts comprehensibility. Also, including the `in the afternoon` breaks the parallel structure of each of the items in the list.

A couple options to improve:

1. circadian rhythms are the 24-hour changes in our physiology that synchronize with the day-night cycle and modulate when we are hungry, sleepy, want sex, or, in the afternoon, have asthma attacks or a fever.

2. circadian rhythms are the 24-hour changes in our physiology that synchronize with the day-night cycle and modulate when we are hungry, sleepy, want sex, or suffer conditions like asthma attacks or fevers.

3. circadian rhythms are the 24-hour changes in our physiology that synchronize with the day-night cycle and modulate when we are hungry (mealtimes), sleepy (nighttime), want sex (??? i didnt know this was a thing), or suffer asthma attacks or fevers (afternoons).