Researchers concluded that the culprit behind the extremely unusual 2019 outbreak was the intestinal pathogen, Campylobacter jejuni. The gut-dwelling bacteria is well-known as one of the most common causes of food poisoning and diarrheal cases in the world. But, less well-known, it's also one of the leading triggers for GBS.
Adding this because I think it's pretty critical for your quotes. So this is something that has been (likely) foodborne in Peru before. But the article implies that only about 2/3 of their identified cases showed signs of the same infection.