Two New York infants were diagnosed with herpes after undergoing an ultra-Orthodox Jewish circumcision ritual, according to reports.

The New York City Department of Health and Mental Hygiene said both baby boys developed lesions on their genitals following the metzitzah b’peh, the practice where the mohel, or circumciser, uses oral suction to remove blood from the circumcision wound, the Jewish Daily Forward reported. The Health Department sent an alert to doctors last week warning them of suspected cases, the newspaper said.

Since 2000, 16 infants in New York City — including three this year — are suspected of contracting the virus after “direct orogenital suction,” according to the Health Department.

Two died and at least two others suffered brain damage.

According to research published by University of Pennsylvania School of Medicine:

HSV-1, which frequently presents itself as oral lesions, or cold sores, though many people never or rarely develop symptoms. Newborns infected with HSV-1, on the other hand, can become very sick quickly with high fever and seizures, and it can even cause death. Herpes simplex virus type 2 is a sexually-transmitted disease and is characterized by genital lesions, and is less common, affecting about 16 percent of adults.

Following a 2012 HSV-1 outbreak, the Health Department attempted to regulate the practice, requiring mohels to obtain written parental consent, “which would provide information about the risks involved, including possible infection with herpes simplex virus and its potentially serious consequences, such as brain damage and death,” the rule stated.

Some Orthodox groups opposed the regulation, arguing it violated religious freedom, according to the Jewish Telegraphic Agency. But a federal judge upheld the regulation in 2013.

Since the regulation was enforced, four infants have contracted the virus, the Forward reported.