The warning was issued for four churches in the Diocese of Fargo where Bishop John Folda participated in services between Sept 29 and Oct. 2, The Jamestown (N.D.) Sun reported Friday.
Folda has since been diagnosed with hepatitis A. He may have contracted the disease from food while he attended a conference in Italy in September.
He has not been in the diocese office since he was diagnosed Oct 10, said Aliceyn Magelky, director of communications for the diocese.
The churches of concern are St. James Basilica in Jamestown and Holy Spirit Church, Cathedral of St. Mary and St. Paul's Catholic Newman Center, all in Fargo, North Dakota Department of Health officials said.
A person with the disease is likely to spread it during the two weeks before symptoms begin, said Molly Howell, the health department's immunization program manager.
Hepatitis A is typically spread by individuals who do not wash their hands after using the toilet or changing diapers and then touch food, she said. It is not spread through the air.
Symptoms include fever, tiredness, loss of appetite, nausea, abdominal discomfort, dark urine, pale stools or jaundice.