The number of confirmed cases of campylobacter infection has increased to 12 — eight in Pennsylvania residents and four in Maryland residents.

Edwin Shank, the owner of Shankstead EcoFarm, trading as The Family Cow in Chambersburg, Pennsylvania, voluntarily halted the sale of milk today but insisted that raw milk samples that the farm sent last week to QC Labs has tested negative for pathogens.

In an e-mailed letter to customers, Shank wrote:

“In spite of some over-eager reporting, there have been NO positive campylobacter tests from unopened container of our raw milk either by the PDA lab or from QC Labs, the certified lab that we use. There are 4 samples, between us and the PDA which are being tested presently. We expect them later today.

“When your emails started pouring in, one thing became immediate obvious. There is an unusually powerful stomach and lower gastrointestinal illness with acute 7-10 day diarrhea going through our communities. Some say it’s nationwide.

“So, if we were looking for an easy way out, and looking to shift the blame, it looks like we could have our answer. It’s not us! It’s not our milk! It’s a virus. It’s the flu. It is nationwide so don’t blame us!”

Testing of the product is still underway at the Pennsylvania Department of Agriculture, which will update the situation daily, according to a spokeswoman.

Epidemiology and DNA fingerprinting are much better tools for solving outbreaks of foodborne illness than simple testing.