CDC warns acute flaccid myelitis is poised for a comeback in kids this fall

As if the novel coronavirus pandemic was not enough! Now the United States Centre for Disease Control and Prevention (CDC) warns parents and pediatricians to be on the watch for a rare condition called Acute Flaccid Myelitis or AFM for short, which could affect young children and cause unexplained muscle paralysis similar to poliomyelitis. Their report is published today in the Morbidity and Mortality Weekly Report.

What is AFM?

Acute flaccid myelitis (AFM) is defined as a rare onset neurological condition by the CDC on their website. It can affect the nervous system around the spinal cord. It specifically affects the gray matter in the spinal cord. This region of the spinal cord is responsible for muscle strength and movement. Its involvement in AFM leads to weakness of muscles and reflexes in the body.

The CDC warns that AFM is similar to polio, and this weakness is typically reminiscent of polio infection, causing sudden onset weakness and paralysis among young children. Since 2014, there have been several cases of AFM, but the stool samples tested show no presence of the poliovirus, says the CDC.

Presentation of AFM

Patients with AFM are more likely to be below the age of five years. In most cases, there is a preceding episode of fever, respiratory tract infection for a few days. After this short illness, which seems to resolve on its own, the child often develops muscle weakness typical of AFM.

The CDC report states, "In addition to weakness, common symptoms at clinical evaluation were gait difficulty (52 percent), neck or back pain (47 percent), fever (35 percent), and limb pain (34%)... Overall, 98% of patients were hospitalized, 54% were admitted to an intensive care unit, and 23% required endotracheal intubation and mechanical ventilation."

After around two years of the infection, most of the patients have not regained full function of their paralyzed muscles, says the CDC. They have followed up with the children and concluded that the disability might be permanent in several cases.

Alternate year spikes

The CDC says that there is an alternate year spike in the number of cases of AFM in the United States since 2014. In 2018 there were 238 cases of AFM among young children, the health body has recorded. There were 120 cases in 2014, 22 in 2015, 149 in 2016, and 35 cases in 2017. This reveals an alternate year spike pattern in the number of cases reported. Typically the condition is more prevalent in children below the age of five years.

Being an alternate year, there is a likelihood that a spike would be seen again this year warns the CDC.

Things will get worse with the coronavirus pandemic, says the CDC. Dr. Thomas Clark, deputy director of CDC's Division of Viral Diseases, said in his statement, "AFM is a priority for CDC as we prepare for a possible outbreak this year." He added, "We are concerned that, in the midst of a COVID pandemic, that cases might not be recognized as AFM, or we are concerned that parents might be worried about taking their child to the doctor if they develop something as serious as limb weakness."

What to do?

According to Dr. Clark, if parents detect any sign of limb weakness or muscle weakness in their young children with or without a brief period of respiratory infection, they need to get their children to the hospital. There may be a pain in the muscles of the limbs as well instead of weakness, the CDC says. Clark says that the current pandemic should not deter parents from getting their children examined in case of such weakness or pain. The CDC website says that early detection could lead to better recovery and prevent long term paralysis or limb weakness.

The CDC emphasizes that any sign of limb weakness in a young child below five years is a medical emergency, and help should be sought immediately.

Causative organism

The CDC statement reads, "Enteroviruses, particularly EV-D68, are likely responsible for the increase in cases every two years since 2014. AFM is a medical emergency, and patients must be hospitalized and monitored in case they progress to respiratory failure." There are other viruses that could be the reason behind AFM. The CDC says adding, "Multiple viruses, including West Nile virus, adenovirus, and non-polio enteroviruses, are known to cause AFM in a small percentage of infected persons."

Experts have found that enteroviruses are common, and infections with these viruses cause 10 to 15 million cases annually in the USA. Summer and fall are the common seasons when there is a peak of these infections. Symptoms mimic a common cold, including fever, body ache, headache, and runny nose. Some children go on to develop AFM after such an episode, while others do not.

Clark said, "We don't yet know why certain kids develop AFM when the great majority who have a respiratory illness recover without neurological symptoms."

Course of the outbreak

According to Dr. Robert Redfield, the CDC's director, the course of this year's outbreak of AFM amidst the coronavirus pandemic is unclear.

He said, "It is not known how the COVID-19 pandemic and the social distancing measures may affect the circulation of viruses that can cause AFM, or if COVID-19 will impact the health care system's ability to recognize and respond to AFM promptly." He added, "If social distancing measures decrease the circulation of enteroviruses this year, AFM cases may be fewer than expected or the outbreak may be delayed."

The CDC, however, warns parents to be careful and alert in case any symptoms of limb weakness develop. The CDC said that the social distancing measures and hygiene and handwashing regimens followed to prevent coronavirus infection could also lead to a reduction in the number of cases of AFM this year.

The authors of the report wrote in conclusion, "Non-COVID-19 emergency department visits declined in 2020, and the pandemic could possibly contribute to delays in care or to an increased proportion of clinical evaluations taking place via telephone or telemedicine. During this time, it will be critical for parents and clinicians to be aware of signs and symptoms suggestive of AFM and maintain vigilance for this condition during 2020."

Journal reference:
  • Kidd S, Lopez A, Nix WA, et al. Vital Signs: Clinical Characteristics of Patients with Confirmed Acute Flaccid Myelitis, United States, 2018. MMWR Morb Mortal Wkly Rep. ePub: 4 August 2020. DOI:
Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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