CDC Update & Statement On Acute Flaccid Myelitis (AFM)

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The CDC has updated their weekly surveillance numbers and has issued a brief statement on cases of Acute Flaccid Myelitis (AFM) - a rare, polio-like illness that has been tentatively linked to several viral infections - adding 18 new confirmed cases since last week's update.

The CDC has now confirmed 134 AFM cases out of 299 patients under investigation (PUIs) in 2018.

The increase in PUIs, however, has slowed the past couple of weeks - and past outbreaks have generally peaked in October - both of which suggest this year's outbreak has probably peaked.

Many of the cases confirmed in the past few weeks actually fell ill in September or October, which means that while new cases are slowing, additional cases are likely to be confirmed in the coming weeks.

While the cause of these polio-like outbreaks remain a mystery, a number of enteroviruses (EV-71, EV-D68, etc.) are high on the suspect list. The CDC notes, however, that most cases have tested negative for any virus.

Paralysis - while exceedingly rare - can appear days or even weeks following a suspected viral infection, which may help explain the lack of positive lab tests. 

It is also possible that this paralysis is due to some sort of autoimmune response to more than one virus,  or even that some unknown virus - not currently picked up by testing - is at work.

First, this media statement from the CDC, followed by some snippets from this week's surveillance update.

Weekly Update for Number of U.S. AFM Cases

2018 case count appears to have peaked

Media Statement

For Immediate Release: Monday, December 3, 2018
Contact: Media Relations

(404) 639-3286

Based on the number of reported cases of AFM in the United States through November 30, 2018, it appears that the number of persons under investigation (PUIs) for AFM has peaked and will continue to decline for the remainder of 2018.

So far in 2018, 134 cases of AFM have been confirmed in 33 states out of 299 cases reported to the CDC. This is an increase of 18 confirmed cases from the previous week, but most of the latest confirmed AFM cases occurred in September and October.

CDC expects states to continue reporting likely AFM cases, and medical experts will continue to review them and determine if they are confirmed. CDC will continue to provide updates on the number of confirmed cases of AFM.

With AFM, CDC has seen a pattern of higher numbers of confirmed cases every 2 years:

• In 2014, CDC confirmed about 120 cases of AFM.
• In 2015, 22 cases of AFM were confirmed by CDC.
• In 2016, the number of confirmed cases increased to 149.
• In 2017, the number of confirmed cases was 33.

Most cases are reported between August and October, and a marked reduction in cases is seen in November. That pattern appears to be repeating in 2018 because states have reported fewer PUIs over the past couple of weeks. CDC expects this decline to continue.

Although fewer cases are expected in coming months, CDC and partners continue to carefully study AFM to gain new understanding of the condition so that we can better diagnose, treat, and prevent it in the future.

AFM Investigation

 What CDC has learned since 2014

• Most of the patients with AFM (more than 90%) had a mild respiratory illness or fever consistent with a viral infection before they developed AFM.
  • Viral infections such as from enteroviruses are common, especially in children, and most people recover. We don’t know why a small number of people develop AFM, while most others recover. We are continuing to investigate this.
• These AFM cases are not caused by poliovirus; all the stool specimens from AFM patients that we received tested negative for poliovirus.
• We detected coxsackievirus A16, EV-A71, and EV-D68 in the spinal fluid of four of 458 confirmed cases of AFM since 2014, which points to the cause of their AFM. For all other patients, no pathogen (germ) has been detected in their spinal fluid to confirm a cause.
• Most patients had onset of AFM between August and October, with increases in AFM cases every two years since 2014. At this same time of year, many viruses commonly circulate, including enteroviruses, and will be temporally associated with AFM.
• Most AFM cases are children (over 90%) and have occurred in 46 states and DC

If you suspect you or your child are suffering from unexplained muscle weakness or paralysis, it is important to seek medical care immediately. The CDC continues to investigate, but until more is known, the CDC can only offer the following advice.

Prevention

Poliovirus and West Nile virus may sometimes lead to AFM.

• You can protect yourself and your children from poliovirus by getting vaccinated.
• You can protect against bites from mosquitoes, which can carry West Nile virus, by using mosquito repellent, staying indoors at dusk and dawn (when bites are more common), and removing standing or stagnant water near your home (where mosquitoes can breed).

While we don’t know if it is effective in preventing AFM, washing your hands often with soap and water is one of the best ways to avoid getting sick and spreading germs to other people. Learn about when and how to wash your hands.

For more information on what CDC is doing, see our AFM Investigation page.

Although Enterovirus D68 and EV-A71 have both been implicated in past cases (along with a number of other viral suspects), for now the jury is out on what has caused the bulk of these cases. A few recent studies include:

mBio: Contemporary EV-D68 Strains Have Acquired The Ability To Infect Human Neuronal Cells

Notes from the Field: Enterovirus A71 Neurologic Disease in Children — Colorado, 2018

Eurosurveillance Review: Association Between Acute Flaccid Myelitis (AFM) & Enterovirus D68 (EV-D68)