Do diseases carry over from polymorph?

I’m curious how polymorph and diseases interact.

Say the following scenario. A character of at least level 5 is polymporphed into a Giant Shark and fights an Aboleth.

Polymorph states the following:

The target’s game statistics, including mental ability scores, are replaced by the statistics of the chosen beast.

The Aboleth has the following attack:

Tentacle. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw or become diseased. The disease has no effect for 1 minute and can be removed by any magic that cures disease. After 1 minute, the diseased creature’s skin becomes translucent and slimy, the creature can’t regain hit points unless it is underwater, and the disease can be removed only by heal or another disease-curing spell of 6th level or higher.

So any ‘normal’ creature can get diseased by the Aboleth. But what happens to the polymorphed character after returning to his normal form?

I can see the following options:

  1. The Giant shark get’s diseased as normally and suffers the effects. When the character returns to his normal form, the disease does not carry over, irrelevant of whether a minute has passed or not. (because all the game statistics have been replaced, including status effects)
  2. The Giant shark get’s diseased as normally and suffers the effects. When the character returns to his normal form, the disease carries over, if it has been more than a minute, because then the disease can no longer be removed by a spell of 4th level like polymorp.
  3. The Giant shark get’s diseased as normally and suffers the effects. When the character returns to his normal form, the disease carries over, irrelevant of whether a minute has passed or not and the character suffers the full effects.

Bonus question: If 2 or 3 is correct, what happens if the character is a paladin?

The paladin has the ‘Divine Health’ feature, which is most likely not present while the paladin is in Shark form, because polymorph replaced his statistics:

By 3rd level, the divine magic flowing through you makes you immune to disease.

But what after he reverts back from being a diseased Giant Shark. His ‘Divine Health’ is not a spell of 6th level or higher, so it should not be able to remove the disease, if it has been a minute. On the other hand, he is immune to diseases. How can he be diseased?

Does the paladin’s Divine Health feature protect against both common and magical diseases?

By 3rd level, a Paladin gains the following ability (PHB, pg. 85):

Divine Health: The divine magic flowing through you makes you immune to disease.

Does this protect against both common AND magical disease?

There is no differentiation between the two. Disease is simply disease in the relevant entries (which I can’t find anymore). A few spells afflict you with disease; sickly common folk may be diseased, and certain magical aura’s on enemies may inflict a diseased state. Since these all count under the ‘Disease’ umbrella, and the Paladin trait simply says a magical energy is making you immune to disease… I assume this is read as “Immune to [all] disease.”

Would a polymorphed undead retain any diseases when it reverts back to normal form

Specifically, if I cast a heightened polymorph a lich, turning it into a sheep or caterpillar or something then cast contagion on it (5th level cleric spell that gives the target a disease of the casters choosing after it fails 3 CON saves) then revert it back to lich via damage, would it still carry the disease?

Do diseases stack?

Say you’re fighting dire rats and get bit 9 times, failing your save each time. If their incubation period rolls are evenly spread, do you take 3d3 Dex/Con damage after 1 day, then possibly 6d3 damage the next day, and 9d3 damage starting once every “instance” of the disease is active?

If that’s not it, then how do diseases stack, if at all? It seems somewhat silly, but I can’t find anywhere in the DMG that says it doesn’t work like this.