TERRA BELLA, Calif. – It could take weeks before health officials know exactly which pistachio products may be tainted with salmonella, but they’ve already issued a sweeping warning to avoid eating the nuts or foods containing them.

The move appears to indicate a shift in how the government handles food safety issues — from waiting until contaminated foods surface one-by-one and risking that more people fall ill to jumping on the problem right away, even if the message is vague.