New York City is investigating the death last September of a baby who contracted herpes after a "ritual circumcision with oral suction," in an ultra-Orthodox Jewish ceremony known in Hebrew as metzitzah b'peh.
In a practice that takes place during a ceremony known as the bris, a circumcision practitioner, or mohel, removes the foreskin from the baby's penis, and with his mouth sucks the blood from the incision to cleanse the wound.
The district attorney's office in Kings County Brooklyn is investigating the death of the 2-week-old baby at Maimonides Hospital, but would not disclose the name of the mohel or whether there would be a prosecution.
"We are looking into it, that's all I can say," a D.A. source told ABCNews.com.
The 5,000-year-old religious practice is seen primarily in ultra-Orthodox and some orthodox communities and has caused an alarm among city health officials. In 2003 and 2004, three babies, including a set of twins, were infected with Type 1 herpes; the cases were linked to circumcision, and one boy died.
The mohel who performed the procedures, Yitzchok Fischer, was later banned from doing circumcisions, according to The New York Times. It is not known if he was involved in this recent death.
"It's certainly not something any of us recommend in the modern infection-control era," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University.
"This is a ritual of historic Abraham that's come down through the ages, and now it has met modern science," he said. "It was never a good idea, and there is a better way to do this." (The modern Jewish community uses a sterile aspiration device to clean the wound in a circumcision.)
In the 2004 death and the more recent one, a mohel infected the penile wounds with Type 1 herpes I (HSV-1), which affects the mouth and throat. It is different from Type 2 or genital herpes (HSV-2), which is a sexually transmitted disease and can cause deadly infections when a newborn passes through an infected birth canal.
Neonatal herpes is "almost always" a fatal infection, according to Schaffner. "It's a bad virus. [Infants] have no immunity and so it's a very serious illness. Now we have another death -- an unnecessary, incredibly tragic death."
Infections are rare, according to a 2009 study in the New England Journal of Medicine, affecting only one infant in 3,200 births. But it is a serious infection, with a fatality rate of about 64 percent even with antiviral treatment. And fewer than 20 percent of those who survive develop normally.
Schaffner was a medical consultant in the 2004 death of the twin, when city and state officials butted heads with religious leaders who defended their freedom to continue the traditional practice.
"Unfortunately, adults can carry the herpes virus without any symptoms," he said. "Applying the mouth to an open wound can transmit the virus, which can disseminate throughout the body of the infant."
Type 1 herpes is common, and 90 percent of all Americans have experienced infection by the age of 50, the vast majority without symptoms, according to Principles and Practice of Infectious Diseases.
About two-thirds of all infant boys born in New York City's Hasidic communities, who are ultra-Orthodox, are circumcised in the oral suction manner, according to Rabbi David Zwiebel, executive vice president of Agudath Israel of America.
"Of course the community is deeply saddened by this terrible tragedy," he wrote to ABCNews.com in an email.
"We really don't know any of the details as yet," he wrote. "Who was the mohel? Did he take the hygienic precautions prescribed by the NYC Health Department in the 2006 protocol it entered with rabbinic leaders of the Orthodox community, which are designed to reduce the risk of transmitting infection?
"Did health officials perform the type of investigation described in the protocols to ascertain the source of the infection? What were the results of any such investigation? It is difficult for us (and should be difficult for anyone else) to comment publicly on this tragedy or to draw any firm conclusions."
Zwiebel said the Orthodox community was "increasingly attuned" to health risks and to the importance of following safety steps.
Earlier this week, he told the New York Times that mohels were aware of the health risks and hygienic practices and warned that regulation could send them "underground."