Tennessee has 66 of the 271 patients sickened with meningitis or joint infections. Eight of the 21 who have died were in Tennessee.
Centers for Disease Control and Prevention spokesman Curtis Allen said it is too early to say whether the rate of new infections is decreasing nationally.
"This is still an ongoing investigation," he said. "There were about 14,000 people exposed."
Not everyone who received the contaminated medicine will get sick, Reagan said. The most important factor determining who does get sick seems to be how much fungus was contaminating the particular vial of medication they received, not their age or even how healthy they were.
"It's not predictable," Reagan said.
Tennessee's meningitis patients range in age from 23 to 91 years old. The majority of them are women, but Reagan said that is only because more of the patients receiving the contaminated injections were women.
Those patients who have been sickest are those who either did not catch the symptoms early or who didn't receive appropriate treatment early because doctors didn't know what they were dealing with. The fungi become harder to kill once they have established themselves in a person's body.
"If treatment is given early, it is very effective," Reagan said. "If it is given late, it is not very effective."
Most of the positively identified cases are caused by Exserohilum rostratum. The fungus is commonly found in the environment, but it has never before been observed as a cause of meningitis.
Because of that, Reagan said, officials have been unable to firmly establish the incubation period and give those who received the tainted injections a date for when they will no longer need to worry about developing meningitis.
"We're saying at least six weeks, or 42 days, but we probably will extend that," he said. "This is new territory. There's no literature to tell us how long."
That uncertainty is causing a lot of anxiety for people who received the tainted injections but haven't developed symptoms. And there's no test that can show someone is in the clear.
Doctors are diagnosing the fungal meningitis cases by collecting spinal fluid with a long needle, but "just because there's no evidence of infection today, that doesn't mean it won't show up tomorrow," Reagan said.
That's why Tennessee health officials are continuing intensive follow-up with the approximately 1,000 patients who received the injections here between June 27 and Sept. 28, when the suspect medication was pulled from clinics.
Reagan said officials are calling patients once a week to check in and calling twice a week if patients report any symptoms. That has included tracking down people who were vacationing out of state or even out of the country. For anyone who cannot communicate clearly by telephone, officials are making home visits.