What is the possessive form of disease
Solution 1:
"Disease symptoms" is a correct, or at least by far the most common usage.
Google search "Lyme disease symptoms" gives 537,000 results and "Lyme disease's symptoms" 242 results.
In "disease symptoms," disease is not a possessive noun but a noun adjunct or modifier. Similar examples are chicken soup and brick wall.
And if anyone disagrees with this...in medical texts, the usage often does not follow strict grammar rules.
By the way, you can use Lyme or Lyme's disease, Crohn or Crohn's disease...