New Delhi, Aug. 4 -- Two people in Michigan have died in what state health officials say are the first confirmed US deaths linked to the ongoing Cyclospora outbreak, marking a significant development in a nationwide foodborne illness surge that has sickened more than 20,000 people.

The Michigan Department of Health and Human Services (MDHHS) announced on Monday that both individuals had underlying health conditions that may have been worsened by severe intestinal illness and dehydration caused by the infection.

The deaths come as federal health authorities continue investigating a large outbreak linked to contaminated lettuce served at Taco Bell restaurants in multiple states.

Here's what we know.

Cyclospora is a microscopic, single-c...