Food safety experts played down the risk of mad cow disease entering America's food supply, a day after a government agency detected the first new case of the disease in the US since 2006.
It was the fourth BSE case discovered in the country and no human version of the illness has been linked to eating US beef.
"What we know is that 3,000 Americans die every year from preventable food-borne illnesses that are not linked" to mad cow disease, said Sarah Klein of the consumer advocacy group Centre for Science in the Public Interest.
"Things like E. coli, salmonella - that's where we should be focusing our attention, outrage and policy."
Two major South Korean retailers suspended sales of US beef in response. But reaction elsewhere in Asia was muted, with Japan saying there was no reason to restrict imports.
"From simply a public health issue, I put it very, very low," Cornell University food safety expert Martin Wiedmann said of the level of concern about the disease.
Maintaining confidence in exports fuelled the nation's monitoring of the beef supply as much as continuing safety concerns, he said.
Tuesday's news came from that monitoring. Routine testing of a dead dairy cow from central California showed the animal had bovine spongiform encephalopathy or BSE, a disease that gradually eats holes in the animal's brain.
US health chiefs were adamant that there was no risk to the food supply - the cow was never destined for the meat market, and the World Health Organisation says humans cannot be infected by drinking milk from animals with BSE.
The US has been guarding against BSE for years since a massive outbreak in Britain that not only decimated that country's cattle but showed that eating BSE-contaminated meat could trigger a human version of the disease.