These verses all note people who have died. Both 39 and 41 speak of people who die in the faith, and confirms the ultimate joy in the Lord for both sets. The people who die in verse 41 are those who die of old age. Those who die in verse 40 die of fevers. The three verses tell us of ways that people die, but only verse 39 does not specifically note the reason. While it is not given, the context of the wars suggests that these are people who have died as a direct of those conflicts.
Cultural: Sorenson has suggested that the fevers mentioned here are suggestive of a tropical climate (John L. Sorenson, An Ancient American Setting for the Book of Mormon [Salt Lake City and Provo: Deseret Book Co., Foundation for Ancient Research and Mormon Studies, 1985], 27.) Of course this fits well with the Mesoamerican location of Book of Mormon events.
We also learn that while there were fevers, there were medicinal plants that were known to the Nephites. There was certainly a large body of botanical knowledge among the Mesoamerican peoples. While not all of the plants have known modern medicinal properties, many do.
Textual: There is no chapter break in the 1830 edition.