It took exactly 14 days, says The Washington Post, from the time state health officials in Wisconsin noticed five cases of E. coli O157:H7 in the same county until investigators arrived Wednesday at a field in California’s Salinas Valley in search of the bacteria that ended up in bagged spinach and sickened 157 people in 23 states.

The outbreak — the largest, in terms of victims, caused by fresh produce — has exposed strengths and weaknesses in the highly fragmented U.S. food safety system. And the extent of it has federal officials talking about imposing tougher regulation.