In 2003 and 2004, the city reported three cases of Type 1 herpes that were linked to circumcision, involving a boy on Staten Island and twin boys in Brooklyn, one of whom died. The procedures were done by one mohel, Rabbi Yitzchok Fischer, who was later prohibited from performing the ritual in New York City.

The authorities have not determined the identity of the mohel in the most recent case, but since the death they have been trying to work with the Hasidic community. In 2004, after the death of the twin, the Brooklyn district attorney tried to investigate but received little cooperation within the community, according to a person with knowledge of the case who spoke on the condition of anonymity because it was not brought to trial.

It was not believed that Rabbi Fischer was under investigation for the latest case, and he did not return a phone call seeking comment. His lawyer from the 2004 investigation, Mark J. Kurzmann, said he would not comment.

Roughly two-thirds of newborn boys in the city’s Orthodox communities are circumcised with metzitzah b’peh, said Rabbi David Zwiebel, the executive vice president of Agudath Israel of America, who said he was using a calculation based on religious school enrollment figures.

He said that the mohels in the Hasidic community were cognizant of hygiene and that there were things they could do to reduce the risk of herpes without ending the practice. “We’re not oblivious to what’s going on,” Rabbi Zwiebel said.