Assuming Your Conclusion

Health officials have said there was a breach in protocol that led to the infections, but they don't know where the breakdown occurred.

Officials have said they also don't know how the first health worker, a nurse, became infected.

 Both quotes are from the same article.

I was struck earlier by headlines asserting that a breech of the protocol, the rules for preventing contagion, had occurred. The basis for that claim was and is the fact that a nurse got Ebola, not any evidence of how it happened. The obvious alternative is that the existing protocols are in one way or another inadequate, possibly because the beliefs about the disease on which they are based are in part mistaken. It is only if you assume that the protocol is correct that you can conclude it was not followed.