Lab-confirmed cases linked to a US outbreak of cyclosporiasis have risen to 1,645, the Centers for Disease Control and Prevention said on Tuesday, up by more than 800 cases from its last update a week ago.

Cases have now been reported across 34 states, and have resulted in 141 hospitalisations as of July 13, according to the health agency. No deaths have been reported.

Cyclosporiasis is an intestinal infection that can be contracted by consuming food typically raw fruits and vegetables or water contaminated with feces, according to the US CDC.

While the United States has experienced outbreaks of the gastrointestinal illness before, the scale and geographic spread of this year’s outbreak are significantly larger, prompting concern among health officials.

The agency cautioned that there is a roughly six-week lag between the onset of illness and the reporting of cases, which means more infections are likely to be identified as additional data is received.

The CDC said it is also aware of more than 5,100 additional cases that require further analysis and confirmation.

The current US outbreak, which began on May 1, is centered in Michigan, with Ohio and New York also reporting high numbers of cases.

Separately, Michigan health officials on Tuesday reported 3,309 cases in the state, an increase of 669 cases since the last update on Monday.

US health officials have not identified the source of contamination and are tracing foods linked to cases through the supply chain, potentially to the farm level, using genetic sequencing where needed.