The Centers for Disease Control and Prevention offices in Atlanta. Photo: Ron Harris/AP

More than half of US states are grappling with an outbreak of gastrointestinal illness caused by a food borne parasite, America’s top health agency reported Tuesday.

Nearly 7,000 confirmed or suspected cases of cyclosporiasis, an infection triggered by a microscopic parasite, have been recorded across 34 states, according to the Centres for Disease Control and Prevention.

The illness “spreads when people consume food or water contaminated with the parasite, typically fresh produce that has not been adequately washed or cooked,” said Gwen Biggerstaff, deputy director of CDC’s Division of Foodborne, Waterborne, and Environmental Diseases.

Symptoms include explosive diarrhoea, loss of appetite, fever and vomiting.