CDC Anticipates 2020 Outbreak of Acute Flaccid Myelitis

Megan Brooks

August 04, 2020

Officials at the Centers for Disease Control and Prevention (CDC) anticipate another peak year for acute flaccid myelitis (AFM) and encourage clinicians to be prepared to recognize AFM and immediately hospitalize patients.

AFM is a medical emergency, CDC Director Robert R. Redfield, MD, said today during a press briefing.

"We are pushing AFM information out far and wide to educate all clinicians, especially frontline providers, to alert and prepare them for increased cases this year," he said.

AFM is a rare but serious neurologic condition primarily affecting children. It is characterized by the sudden onset of arm or leg weakness that can progress quickly; patients can become paralyzed over the course of hours or days and require a ventilator to help them breathe. Some patients will be permanently disabled.

Details of 2018 Outbreak

Since 2014, cases of AFM in the United States have spiked every 2 years between August and November. The largest outbreak occurred 2 years ago, in 2018, with 238 confirmed cases in 42 states.

Enteroviruses, particularly enterovirus-D68, are likely responsible for these peaks in cases, insofar as these viruses tend to circulate every 2 years, Redfield said.

"This means that it will be circulating at the same time as influenza and other infectious disease, including COVID-19, and could be another outbreak for clinicians, parents, and children to deal with," Redfield said.

In a Vital Signs report released today, CDC researchers describe the characteristics of the 238 AFM cases from 2018.

Most cases were in young children (mean age, 5.3 years); 58% of the patients were male; and 86% of the cases occurred during August and November.

Most children who developed AFM had fever or respiratory illness about 6 days before the onset of limb weakness. Once limb weakness developed, it was common for them also to have difficulty walking, as well as neck or back pain, limb pain, and fever.

"Clinicians should suspect AFM in patients with sudden limb weakness, especially during the months of August through November. Recent respiratory illness or fever in the presence of neck or back pain or any neurological symptom should heighten the clinicians concern," Redfield said.

In the 2018 outbreak, approximately three quarters of patients were brought to medical care within 1 day. Most went to the emergency department. Overall, 98% of patients with AFM were hospitalized; 54% were admitted to intensive care units; and 23% required mechanical ventilation.

Speaking at the briefing, Thomas Clark, MD, MPH, pediatrician and deputy director of the Division of Viral Diseases at CDC, noted that although most patients were hospitalized within 1 day of developing limb weakness, 10% were not hospitalized until 4 or more days after developing limb weakness.

"This could indicate delays in recognition of AFM and present an opportunity for improvement in patient outcomes," Clark said.

He noted that enterovirus-D68 was the most common virus identified among specimens tested from patients. Poliovirus, a vaccine-preventable cause of paralysis, was not detected in any of the cases. Patients who tested positive for enterovirus-D68 typically had more severe AFM and were more likely to require intensive care and ventilation.

"All clinicians should remain vigilant for AFM and promptly evaluate patients," Clark said in a statement. "During the COVID-19 pandemic, this may require adjusting practices to perform clinical evaluations of patients by phone or telemedicine. However, clinicians should not delay hospitalizing patients when they suspect AFM," he added.

Morb Mortal Wkly Rep. Published online August 4, 2020. Full text

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