The restaurant probably isn't the defendant

Food is a product

In most states contaminated food is treated as a defective product, which means strict liability applies. You generally don't have to prove anyone was careless — only that the food was contaminated when it left the defendant's control, that you consumed it, and that it caused your injury.

Everyone in the chain

Strict liability generally reaches every commercial seller in the distribution chain, down to the retailer.

• The grower or producer — contamination in leafy greens, sprouts, melons, and shellfish frequently originates at the farm through irrigation water or runoff
• The processor or manufacturer — where most large multistate outbreaks originate, because one facility's failure distributes nationally
• The distributor
• The retailer or restaurant

When the restaurant is the right defendant

Sometimes the failure is genuinely local, and the pattern is recognizable.

• An infected food handler — the usual source in norovirus and hepatitis A clusters, and often traceable to a sick-leave policy that pushed people to work ill
• Temperature abuse — food held in the danger zone, documented by inspection reports
• Cross-contamination between raw and ready-to-eat food
• Inadequate cooking
• Poor handwashing infrastructure or documented sanitation failures

Why upstream matters practically

An independent restaurant may carry a general liability policy in the low seven figures at best, and a serious foodborne illness case — hospitalization, dialysis, permanent kidney damage — can exceed that quickly. A national processor carries orders of magnitude more coverage and has traceback records that identify the source.