Most of the infections have been in the Shia Muslim holy city of Qom.
"The virus came from China to Qom city. A merchant from Qom who died of the virus used to regularly travel to China ... Flights were suspended between the two countries but he used indirect flights," Health Minister Saeed Namaki said.
"Obviously we do not recommend trips to Qom or any other holy Shia cities in Iran," Namaki said on state television.
Health Ministry spokesman Kianush Jahanpur announced the 15 new cases earlier on Sunday.
"So far, we have 43 infected cases and the death toll is eight," he told the television.
Eight of the new infections were in Qom, where authorities have shut down schools and religious seminaries. In Tehran and some other cities, schools have been closed until Tuesday.