In the case where mohel had 2 [mortality] cases without other explanation, he should refrain from doing MB'p (Metzitzah B’peh), until it is proved he is not cause.
We were considering that if mohel were cultured a certain number of times (50? 100?)and no (Herpes simplex) virus was find, we could assume that he is not a "shedder,"or such a rare shedder, that he is not the likely cause of the infection and aloow him to resume his practice.
How would you deal with this situation?
The principle in Dinei Chazaka that we must be choshesh after two occurrences, is based on the prerequisite of a possible single cause for both cases, as in the case of the woman who lost two children after Mila, where there is a possible underlying genetic condition (such as hemophilia); also – in the case of the Mohel that two of the babies circumcised by him developed HSV-1, where there is the possible scenario of infection by the Mohel.
But if it was proven that the Mohel is not a carrier of the herpes simplex virus, this possibility is no longer possible, and therefore the chazaka no longer exists.
Example: when two brothers died Mechamat haMila, and a medical investigation shows that they did not die from hemophilia but from hemolytic anemia – which is a transient phenomenon. In such a case it is permissible to wait for the hemoglobin levels to rise sufficiently and then circumcise as discussed in the Gemara (Shabbat 134a) in the case of Natan haBavli