Might have to put a longer pause on those drunk, late-night Taco Bell visits ... because the explosive diarrhea parasite is starting to go national ... and the fast food chain is under investigation for a possible connection to the outbreak.

According to The Washington Post ... the investigation is ongoing, with leafy lettuce as the leading suspect on what's causing the outbreak ... but that doesn't mean other food items can be ruled out.

More than 2,600 cases have hit in Michigan alone ... and now 30 states are reporting higher numbers of illnesses. Nationwide, more than 80 people are hospitalized.

As you know ... Taco Bell recently removed several fresh ingredients -- including lettuce, pico de gallo, guacamole, and its cilantro-onion blend -- from some locations while health officials investigate the surge in cyclospora ... and according to The Washington Post, a person familiar with the national investigation said that decision was certainly appropriate.

The outbreak has turned Taco Bell diarrhea jokes into an eruptive reality ... with parasites that infect the intestines, causing watery diarrhea and frequent "explosive" bowel movements ... according to the Centers for Disease Control and Prevention.