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The CDC has updated their weekly surveillance number on cases of Acute Flaccid Myelitis (AFM) - a rare, polio-like illness that has been tentatively linked to several viral infections - adding 10 new confirmed cases since last week's update.
The CDC has now confirmed 116 AFM cases out of 286 patients under investigation (PUIs) in 2018. Investigating each case takes time, and so more from this group may be confirmed in the weeks to come.Outbreaks of AFM in the United States first surged in 2014, and were originally linked to coincident outbreaks in EV-D68, a relatively rare non-polio enterovirus (NPEV). A second, similar outbreak was reported in the fall of 2016, but no concurrent outbreak of EV-D68 was noted (see graph below).
This 2018 outbreak looks on track to equal - or even exceed - the first two outbreaks, although better awareness could be affecting the reporting of cases.
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.
Some excerpts from the latest CDC update:
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 440 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.
Two weeks agp the CDC posted an hour-long COCA Call AFM: What Healthcare Providers Need To Know, published an MMWR Early Release Increase in Acute Flaccid Myelitis — United States, 2018, and held a tele-briefing (audio 5mb) to update reporters.
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.
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.
- 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).
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)
