The correct spelling of the phrase "Disease Cat" is without a space, as "diseasecat". This can be explained using the International Phonetic Alphabet (IPA). In English, we have something called compound words, which are formed by combining two or more words to create a new word with a new meaning. When we say "diseasecat", we are essentially creating a compound word by putting together "disease" and "cat". The lack of a space between the two words signifies that they should be pronounced as one unit.