The toll includes 496 cases of central nervous system infection, usually involving meningitis, and 14 cases of peripheral joint infections, the agency reported.
The update is the first since Nov. 19, when the CDC reported 490 cases (including 12 joint infections) and 34 deaths.
The outbreak began in late September, when Tennessee doctors began treating a man for an unusual form of meningitis that did not seem to have a bacterial or viral cause.
Eventually, they found evidence of a fungal infection – with the mold Aspergillus fumigatus – and notified the state’s public health authorities.
Investigation linked injections of a steroid, methylprednisolone acetate, to the index case and to several subsequent cases. The drug was injected into the spine to control chronic back pain and, in some cases, into painful joints.
The steroid, manufactured in large quantities by a Framingham, Mass., compounding pharmacy – the New England Compounding Center (NECC) – was later found to be contaminated with a fungus, although not with Aspergillus.
Instead, suspicion has now come to rest on a black mold, Exserohilum rostratum, one of a group of organisms whose members only rarely cause human disease. The fungus was found in some vials of the steroid and also in several of the affected people, although it has proved difficult to isolate from many patients.
The fallout from the outbreak has included recalls of all drugs made by NECC and a sister company, Ameridose, of Westborough, Mass. There has also been intense discussion of how so-called compounding pharmacies are regulated and what safeguards are or should be in place.
NECC had shipped 17,000 vials of three lots of the tainted steroid to 23 states. The CDC has said about 14,000 people were exposed to the substance and cases of disease have been found in 19 of those.
Currently, the highest toll is in Michigan, where there have been 178 cases (including 10 joint infections) and 10 deaths. Tennessee, where the outbreak was first recognized, has reported 84 cases (with no joint infections) and 13 fatalities.
Indiana and Virginia have reported 57 and 51 cases and 6 and 2 deaths respectively, with no joint infections in either state. The remaining 15 states are reporting lesser impacts.