Image caption Creutzfeldt-Jakob Disease can only be diagnosed through biopsy or post-mortem examination

Thirteen hospital patients in the US states of Massachusetts and New Hampshire may have been exposed to a fatal brain disease, officials say.

Authorities say potentially infected surgical equipment was used in procedures at two hospitals.

They suspect a brain surgery patient had Creutzfeldt-Jakob Disease, which has proteins that can survive standard sterilisation measures.

There is no known treatment or cure for the extremely rare disease.

Symptoms of the condition, similar to mad cow disease, include progressive dementia and can cause death within months.

The patient at the centre of the inquiry had brain surgery at New Hampshire's Catholic Medical Center in May and died in August.

Tests are being carried out to determine if the patient had Creutzfeldt-Jakob Disease. Eight patients who underwent brain operations at the hospital have been advised of the risk.

Five patients who underwent spinal procedures at Massachusetts' Cape Cod Hospital - which borrowed an instrument used on the New Hampshire patient - have also been contacted, say health officials.

But they stress the possibility of transmission is remote.

About 200 cases of Creutzfeldt-Jakob disease are reported annually in the US. There have been only four reported cases of transmission via surgical instruments, all outside the US.