From The NY Times:
[New York City Health Commissioner Dr. Thomas R. Frieden] said the department regarded herpes transmission via oral suction as "somewhat inevitable to occur as long as this practice continues, if at a very low rate"...
Defenders of oral suction say there is no proof that it spreads herpes at all. They say that mohels use antiseptic mouthwash before performing oral suction, and that the known incidence of herpes among infants who have undergone it is minuscule. (The city's health department recorded cases in 1988 and 1998, though doctors in New York, as in most states, are not required to report neonatal herpes.)
Dr. Kenneth I. Glassberg, past president of the New York section of the American Urological Association and director of pediatric urology at Morgan Stanley Children's Hospital of New York-Presbyterian, said that while he found oral suction "personally displeasing," he did not recommend that rabbis stop using it.
"If I knew something caused a problem from a medical point of view," said Dr. Glassberg, whose private practice includes many Hasidic families, "I would recommend against it."