59 the LORD will send fearful plagues on you and your descendants, harsh and prolonged disasters, and severe and lingering illnesses.

Read Deuteronomy 28:59 Using Other Translations

Then the LORD will make thy plagues wonderful, and the plagues of thy seed, even great plagues, and of long continuance, and sore sicknesses, and of long continuance.
then the LORD will bring on you and your offspring extraordinary afflictions, afflictions severe and lasting, and sicknesses grievous and lasting.
then the LORD will overwhelm you and your children with indescribable plagues. These plagues will be intense and without relief, making you miserable and unbearably sick.