Yesterday I looked at teacher absence in the developing world, highlighting India where a quarter of teachers may be absent on a given day. Teacher absence isn't that high in the United States but it is still shockingly high. On a typical school day, 5-6% of teachers are absent, i.e. equivalent to an absence once every 20 days!
Bearing in mind that the typical school year is 180 days, add absences to all the school holidays, teacher workdays, staff development days (btw, ever seen a Walmart shutdown for a staff development day?), and other non-teaching days (e.g. in Fairfax, Mondays are half-days) and the number of days of true teachng greatly diminishes.
Teachers probably do get sick more often than other workers but teacher absence rates are three times higher than for managers and professional employees in the private sector. Moreover, are you surprised to learn that teacher absences are most frequent on Mondays and Fridays or that teacher absences are of a duration just short of that requiring medical certification of illness?