Federal and state health officials are trying to identify any more cases of a deadly fungal meningitis that they suspect resulted from an injected steroid commonly used to treat back pain. The drug, made by a Massachusetts company that has suspended operations, was apparently contaminated by a common leaf mold. So far 35 people have gotten sick in six states and five have died. But thousands more may have received the tainted drug. The incubation period can be as long as a month, so the danger period may not be over until late October.