Surging sales of counterfeit fetal bovine serum are threatening the safety of pharmaceuticals and vaccines, particularly in China (see Nature 545, 148–150; 2017). To help tackle the problem, GE Healthcare in the United States has launched a screening programme with the product-traceability firm Oritain in Dunedin, New Zealand, to swiftly pinpoint the country of origin of serum samples and provide an indicator of the likelihood of contamination.

As a by-product of the meat industry, fetal bovine serum may contain infectious agents such as that responsible for bovine spongiform encephalopathy. The risk varies by country, depending on disease prevalence. Users therefore prefer serum from low-risk countries such as Australia, New Zealand or the United States. This drives up the price of such premium material and creates an incentive to mislabel the country of origin for fetal bovine serum from higher-risk countries.

Counterfeit samples carrying fake labels are easily spotted. Authentic bottles refilled with bogus material are not, which is where our test comes in (see go.nature.com/2w7dbth). As a result of the food and water they consume, cows carry a distinct trace-element fingerprint from their country of origin. The test identifies the fingerprint by screening it against reference standards.

Our programme could be used to complement the existing paperwork system for verifying authenticity.