Meningitis: CDC reports wide variation in attack rates among states

10:29 PM, Dec 19, 2012   |    comments
Patient receives Meningitis vaccination/AP
  • Share
  • Print
  • - A A A +

By Tom Wilemon / The Tennessean 

Maryland might be expected to have a higher case count of fungal meningitis than Tennessee because more people there were exposed to recalled medicine linked to the outbreak, but illnesses from Tennessee easily quadrupled those reported from the Chesapeake Bay State.

An article published Wednesday in The New England Journal of Medicine showed wide variations in attack rates, but provided no firm conclusion as to the reason. Tennessee had an attack rate of 10.9 infections per 100 people, compared to just 2.4 for Maryland. The national attack rate was 4.7. Both Tennessee and Michigan had attack rates more than double the national average.

"These attack rates are most certainly underestimates, because this outbreak is certainly not over," said Dr. Rachel M. Smith, an epidemiologist with the U.S. Centers for Disease Control and Prevention, who is the lead author of the article.

However, the death rate turned out to be much less than CDC officials initially feared, she said. As of Dec. 10, it was 6 percent of those who became ill. Officials worried it might go as high as 40 percent based on outcomes from much smaller outbreaks of fungal meningitis traced to contaminated spinal injections. Efforts by the CDC, state health departments and health care facilities to contact patients for early diagnosis and treatment saved lives, Smith said.

Possible reasons given for the variation in state attack rates include differences in the degree of contamination in the medicine shipments, the storage times for the medicine and injection practices at the clinics.

However, Smith said CDC staff do not believe some states are missing infections. More than 99 percent of the 13,534 potentially exposed patients had been contacted by Oct. 19.

Another article about the outbreak published in The New England Journal of Medicine last month drew a correlation between storage times and attack rates. Dr. Marion Kainer, state director of healthcare-associated infections for the Tennessee Department of Health, was its lead author.

"We found a strong association between the age of the methylprednisolone vials and the rate of infection in one clinic," the prior article stated. "One possible explanation for this observation is that the level of contamination in the vials may have increased over time, with subsequent high fungal burdens present in older vials."

Today's article in the medical journal includes authors from the CDC and state epidemiologists from Tennessee, Michigan, Indiana, Virginia, Maryland, New Jersey, Florida and North Carolina.

With input from multiple locations and national data compiled by the CDC, it offers the broadest picture of the outbreak thus far. The median age for someone sickened in the outbreak was 64. The youngest meningitis victim was 16, while the oldest was 92.

Women accounted for 61 percent of meningitis cases and 60 percent of all fungal infections. While meningitis has been the most deadly illness associated with the outbreak, patients have also been sickened with injection site infections.

The median incubation period from exposure to illness was 20 days, but some patients didn't get sick until 120 days later.

The peak period for new infections was late September to early October.

What batch of the three recalled lots of methylprednisolone acetate a patient got has been identified as risk indicator. The one linked to the most infections was twice as likely to make a patient sick as a second lot and more than five times as likely to cause an infection as the third lot.

However, Smith said the reason for the variation in attack rates in the three lots is unclear. For instance, one of the lots might have had a higher attack rate if it had been more widely used, she said.

The majority of the 20 to 50 new cases being reported each week are injection site infections. These present diagnosis challenges because pain is a symptom that patients already suffer.

"We're coming out at the CDC with a health alert that kind of talks a little bit more explicitly about guidance in terms of using MRIs in patients with new or worsening pain or even a baseline amount of pain because many of these patients have chronic pain," Smith said. "It's very hard for clinicians to know if their pain is getting worse or just not resolving. We just want to be clear. Some patients even with baseline pain may have evidence of infection on MRI."

Most Watched Videos