An outbreak of cyclosporiasis, a parasitic infection that causes prolonged and often "explosive" watery diarrhoea, has surpassed 1,000 cases in Michigan, marking the largest outbreak of its kind in the state's history and one of the biggest in the United States in years. Cases are climbing across the country as the summer season progresses, and the US Centers for Disease Control and Prevention (CDC) is investigating, though the source of the infections has not yet been identified and no deaths have been reported.

Michigan has now recorded more than 1,200 cases and at least 40 hospitalisations, far above its usual annual total of around 50, with the outbreak announced last week after more than 170 cases were identified in the state's south-east since 22 June. Neighbouring Ohio has reported over 500 cases, mostly in its north-western counties, and infections have appeared in 28 other states, including at least 48 in Texas. Symptoms include severe cramping, bloating, nausea, fatigue and weight loss, and while the illness can clear on its own, it often requires antibiotics. The CDC's official outbreak season runs from 1 May to 31 August, when warmer weather typically coincides with a rise in cases.