At least 20 people have died and another 257 have been infected by the outbreak of deadly meningitis, linked to a contaminated drug, a federal health agency has said.

The disease has now spread to 16 States, the Centers for Disease Control and Prevention (CDC) said, adding that it and Food and Drug Administration are currently coordinating a multistate investigation of fungal infection among patients who received a steroid injection with a potentially contaminated product.

"Given that fungal infections of this kind have never been seen before, the doctors caring for these patients are going to need guidance," said John Jernigan, Clinical Team Lead of the Multistate Meningitis Outbreak and Director of the Office of Health Associated Infections Prevention Research and Evaluation, Division of Healthcare Quality Promotion, US Centers for Disease Control and Prevention.

As such, he said, the CDC has convened the nation's top clinical fungal experts to work with it in developing diagnostic and treatment guidance for physicians caring for these patients.