CDC Expresses Concerns Regarding Increase in Number of Acute Flaccid Myelitis Cases

The Centers for Disease Control and Prevention (CDC) has expressed concern regarding an increase in the number of cases of a polio-like condition, acute flaccid myelitis—a rare condition that affects the nervous system, specifically the spinal cord, and causes weakness in the arms or legs—in the United States.

In a telebriefing held earlier this week, Nancy Messonnier, MD, the director at the CDC’s National Center for Immunization and Respiratory Diseases, reminded reporters that despite the increase in cases, it is still an extremely rare condition, with less than 1 million individuals affected each year in the United States.

From August 2014 to September 2018, the CDC received information on a total of 386 confirmed cases of the condition throughout the United States, with 62 confirmed cases spanning 22 states in 2018, thus far. Many of the infections are occurring among children, with the average age of those infected being 4 years.

When asked if she thought growing awareness about AFM is contributing to greater numbers, Dr. Messonnier seemed to doubt that theory.

The sudden weakness onset leads to seeking medical care; the patients are evaluated by neurologists, infectious disease doctors, as well as the pediatricians. It could be theoretically possible that patients with milder cases of the disease haven’t been reported, Dr. Messonnier admitted; however, she believed the CDC is seeing the majority of cases and that’s leading to their efforts to spread the word and encourage those who are potentially affected to seek medical care.

The CDC still has several unanswered questions about the root cause of AFM. They have ruled out polio and West Nile virus as causes for the cases, though they continue to explore other viruses, environmental toxins, as well as other avenues.

The increase in acute flaccid myelitis cases that were reported in 2014 coincided with a national outbreak of enterovirus D68 (EV-D68) associated with severe respiratory illness; however, the CDC did not consistently detect EV-D68 in every patient with confirmed acute flaccid myelitis.

Dr. Messonnier added that there has not been any significant geographic clustering, and the peaks of the disease have been late summer and early fall—though every other year, in 2014, 2016, and now, 2018.

This year, the CDC believes cases of AFM are generally on track to match numbers from previous disease peaks; it’s too premature to say that they know exactly how it will progress this year though, because they haven’t had the same amount of time to study and diagnose the diseases in this year’s patients compared with other years.

The infection confirmation is another hurdle to clear, Dr. Messonnier said. After symptomology—which includes muscle weakness, muscle tone loss, and paralysis—diagnosis is also confirmed after specific markers found in MRI scans. The case definition must include those findings, rather than the identification of a pathogen, as that is still an unknown factor.

As is typical CDC protocol, they are gathering information after case detection through working with their state and local partners as well as hospitals; they are also testing specimens from suspected cases. The CDC has also been working on promoting awareness of the disease in hopes that health care providers will be better able to recognize the condition among their patients and pass along any information about suspected cases to their health departments.

Also, this year, compared with the 2016 cycle, the CDC has expanded their panel of external experts which were convened to help the CDC with certain processes. Dr. Messionnier said they want to make sure they are carefully thinking through epidemiological and clinical procedures. She added that anyone with relevant information has been included in these discussions.

Rare Disease Report^® will continue to follow the investigation and share more information as it becomes available.