Bacteria, viruses, and parasites can cause a wide variety of illnesses, and can infect any of the organs of the body. Viruses are often responsible for respiratory illnesses (such as the common cold) and digestive illnesses (such as diarrhea).
Disability will not pay for any more time off work than that for pregnancy. After that, many employers let you stay off for the full 3 months for maternity leave but the disability cuts off after 6 or 8 weeks, depending on how you delivered. That's not just how Aflac does it, that's how all disability works.
While 40 weeks is a full term pregnancy, many OB/GYNs consider a pregnancy full term and safe to deliver between 38-40 weeks of gestation. The risk of complications during and after delivery is much lower after a pregnancy has reached the 38th week.