I read recently that during the Mid Republic, it's likely that nearly every adult man in Roman Italy had seen military service, with as many as half experiencing a major battle. Given how deadly war is even without battles, it made me wonder what kind of losses Roman legions took from disease, hunger, exhaustion, etc. I'm most familiar with the Early Modern period, where 'wastage' could deprive an army of 2% of its strength every month. Perhaps a third of all Frenchmen enlisted during the 23 years of Revolutionary and Napoleonic Wars died during their service.
Applying similar loss rates to the Mid Republic period, you see staggering death on a society-wide scale. For an army of 100,000, with men serving 3 year terms, 2% monthly losses during 6 months of campaigning per year gives you a 36% chance of dying during your active service. In the 33 years between the beginning of the First and ending of the Third Macedonian Wars,, more than a million Italians probably served in the Roman army; if 36% of them died, that's just under 400,000 dead, out of a population of less than five million.
Is there evidence that Roman armies suffered death on this scale outside of major battles, or were Roman rates of wastage and attrition lower than in later periods?
We had a discussion a while back in :How many Roman legionnaires survived to retirement?
which has a lot of grist for this mill, and u/Tiako dug up a most helpful reference, a paper by Walter Scheidel "Marriage, families, and survival in the Roman imperial army: demographic aspects"
Roman funerary stela are a particularly rich source, together with other sources this enables Scheidel and others to build something of a statistical model for military survival, and there is some evidence that as you suggest this may have differed by period. The evidence that we have for most periods is that the baseline risk of dying from disease was likely greater than from combat
There are likely periods with greater and lesser military losses, but as Scheidel notes
The demographic impact of campaigning is impossible to quantify. For the period from 200 to 168 BC, Nathan Rosenstein calculated an average combat mortality rate of 8.8% for Roman troops that were actively involved in – documented – battles (ranging from 4.2% for victories to 16% for defeats). If troops that did not see battle are included in the tally, the mean annual combat fatality risk for those years drops to 2.6% even when we allow for some unreported deaths in minor engagements. These estimates are tenuous and in any case cannot be applied to later periods: for the standing army of the Principate, annual combat mortality of the order of 2.6% of total troop strength would translate to some 8,000-10,000 battle fatalities per year. Given what we know about the scale and frequency of large-scale military activity in this period, this notion is wildly implausible. We may conclude that relative to total manpower, combat mortality in the Principate was much lower than it had been in the Mid-Republic
So your intuition is supported by some data, but "tenuous" is a necessary warning that must be applied to interpretations.
See
Rosenstein,Nathan. "Rome at war: farms, families, and death in the Middle Republic", (UNC Press: 2004)
Scheidel, Walter. Marriage, families, and survival in the Roman imperial army: demographic aspects in Princeton/Stanford Working Papers in Classics, online, November 2005
Scheidel, Walter. ‘Roman age structure: evidence and models’, Journal of Roman Studies 91 (2001), 1-26