In August of 2014 the CDC began tracking a sudden increase in Acute Flaccid Myelitis (AFM) cases which were tentatively linked to EV-D68 - a relatively rare non-polio enterovirus - that at the time was causing a nationwide outbreak of mild to moderate respiratory, mostly among children and teenagers.
Acute flaccid myelitis (AFM) is a rare illness that affects a person’s nervous system, specifically the spinal cord. AFM falls under a broader `umbrella' of syndromes called Acute Flaccid paralysis (AFP). AFM may be due to a variety of causes, including viral infection.The number of AFM cases dropped by nearly 80% in 2015 (see chart above), but spiked again in 2016 - notably without a concurrent EV-D68 outbreak spreading across the nation.
There are other viruses - including EV-71, West Nile Virus, cytomegalovirus and Epstein-Barr virus, along with some of the adenoviruses - that are known to cause similar neurological symptoms.While a circumstantial case has been posited to link AFM to EV-D68 over the past few years (see EID Journal Enterovirus D68 Infection in Children with Acute Flaccid Myelitis, Colorado, USA, 2014), no definitive causal link has been established.
The CDC's AFM Investigation page notes:
- CDC is concerned about AFM, a serious condition that causes weakness in the arms or legs.
- From August 2014 through August 2018, CDC has received information on a total of 362 cases of AFM across the US; most of the cases continue to occur in children.
- Even with an increase in cases since 2014, AFM remains a very rare condition. Less than one in a million people in the United States get AFM each year.
- It’s always important to practice disease prevention steps, such as staying up-to-date on vaccines, washing your hands, and protecting yourself from mosquito bites.Acute flaccid myelitis (AFM) is a rare condition. It affects a person’s nervous system, specifically the spinal cord. AFM or neurologic conditions like it have a variety of causes such as viruses, environmental toxins, and genetic disorders.
Since August 2014, CDC has seen an increased number of people across the United States with AFM. We have not confirmed the cause for the majority of these cases. CDC has been actively investigating these AFM cases, and we continue to receive information about suspected AFM cases.As the chart at the top of this blog shows, there's been another - albeit smaller - uptick in cases reported to the CDC since mid-summer. Below we have a statement, issued on Friday, by the Minnesota Department of Health on 8 recent cases in their state.
Statement on cases of acute flaccid myelitis
The Minnesota Department of Health (MDH) issued the following statement today regarding reported cases of acute flaccid myelitis (AFM) in six children around the state over the last few weeks. AFM is a rare but potentially severe condition that can arise following an infection, and in some cases it can lead to death, paralysis or other long-term health impacts.
The Minnesota Department of Health (MDH) is investigating six cases of a rare condition called acute flaccid myelitis (AFM) that occurred since mid-September in Minnesota children.
- AFM is a rare but serious condition that affects the nervous system, causing muscles to weaken. It can be a complication following a viral infection, but environmental and genetic factors may also contribute to its development. AFM symptoms include sudden muscle weakness in the arms or legs, sometimes following a respiratory illness. Other symptoms may include:
- Neck weakness or stiffness
- Drooping eyelids or a facial droop.
- Difficulty swallowing or slurred speech.
MDH disease investigators are working aggressively with health care providers to gather information about the cases. The department is also in contact with the Centers for Disease Control and Prevention (CDC) to share information.
For reasons not fully understood, AFM affects mainly children. All recent Minnesota cases have been in children under 10 years old and all were hospitalized. Cases have been reported from the Twin Cities, central Minnesota and northeastern Minnesota.
There was a national uptick in AFM cases in 2014. Disease investigators believe this was linked to an outbreak of a respiratory illness in children that was caused by a virus known as enterovirus D 68 (EVD68). Minnesota saw three AFM cases that year. Since then, we have typically seen less than one case a year.
Since AFM can develop as a result of a viral infection, MDH recommends parents and children take basic steps to avoid infections and stay healthy:
If parents see potential symptoms of AFM in their child, (for example, if he or she is not using an arm) they should contact their health care provider as soon as possible. AFM can be diagnosed by examining a person’s nervous system, taking an MRI scan and testing the cerebral spinal fluid. It is important that tests are done as soon as possible after someone develops symptoms. While there is no specific treatment for AFM, doctors may recommend certain interventions on a case-by-case basis.
- Wash your hands frequently to limit your exposure to germs.
- Cover your cough or sneeze.
- Stay home if you are sick.
- Stay up to date on vaccinations.
- Protect yourself and children from mosquito bites if you’re spending time outside.
Again from the CDC's AFM Investigation website:
What We Know
Since 2014, CDC has learned the following about the AFM cases:
- Most patients are children.
- The patients’ symptoms have been most similar to complications of infection with certain viruses, including poliovirus, non-polio enteroviruses, adenoviruses, and West Nile virus.
- Enteroviruses most commonly cause mild illness. They can also cause neurologic illness, such as meningitis, encephalitis, and AFM, but these are rare.
- CDC has tested many different specimens from AFM patients for a wide range of pathogens (germs) that can cause AFM. To date, no pathogen (germ) has been consistently detected in the patients’ spinal fluid; a pathogen detected in the spinal fluid would be good evidence to indicate the cause of AFM since this condition affects the spinal cord.
- The increase in AFM cases in 2014 coincided with a national outbreak of severe respiratory illness among people caused by enterovirus D68 (EV-D68). Among the people confirmed with AFM, CDC did not consistently detect EV-D68 in every patient. During 2015, CDC did not receive information about large EV-D68 outbreaks in the United States, and laboratories reported only limited EV-D68 detections to CDC’s National Enterovirus Surveillance System (NESS). During 2016, CDC was informed of a few localized clusters in the United States. Learn more about EV-D68.
What We Don’t Know
Among the people who were diagnosed with AFM since August 2014:
- The cause of most of the AFM cases remains unknown.
- We don’t know what caused the increase in AFM cases starting in 2014.
- We have not yet determined who is at higher risk for developing AFM, or the reasons why they may be at higher risk.
- We do not yet know the long-term effects of AFM. We know that some patients diagnosed with AFM have recovered quickly, and some continue to have paralysis and require ongoing care.
See prevention for information about how to protect your family from viruses that may cause AFM.Despite the continued uncertainty, we've seen other AFM outbreaks around the globe tentatively linked to EV-D68, some of which I've covered in these past blogs.
Eurosurveillance Review: Association Between Acute Flaccid Myelitis (AFM) & Enterovirus D68 (EV-D68)