Anyone who has been following the outbreaks of Acute Flaccid Myelitis the last few years will likely think the following report is long overdue.
The report, Enterovirus D68–Associated Acute Respiratory Illness — New Vaccine Surveillance Network, United States, July–October,2017 and 2018, is especially welcome by those folks who are already convinced that AFM is associated with EV D68.
The New Vaccine Surveillance Network Report on Enterovirus D68 Infections
But wait, why was surveillance done through the New Vaccine Surveillance Network?
And for that matter, what is the New Vaccine Surveillance Network?
“The New Vaccine Surveillance Network (NVSN) includes study sites that focus on population-based surveillance and data collection on the use and impact of vaccines and the impact of vaccine policies. Since 2006, NVSN sites have conducted active, population-based surveillance for hospitalizations and outpatient visits associated with acute gastroenteritis (AGE) in children (2006-present). NVSN sites have conducted surveillance for acute respiratory illness (ARI) from 2000 to 2009, and again beginning in 2015.”
New Vaccine Surveillance Network (NVSN)
Before you start thinking that this means a new Enterovirus D68 vaccine is coming out soon, many NVSN studies have nothing to do with vaccines…
“NVSN supports broad-based surveillance and research projects for acute gastroenteritis and acute respiratory infections in areas with a population base of at least 500,000.”
New Vaccine Surveillance Network (NVSN) Overview
In addition to studies on the flu and pneumococcal disease, they have done studies on norovirus, coronavirus, human metapneumovirus, HPIV, RSV, and rhinovirus infections.
So what did they find out about Enterovirus D68 infections?
“Based on preliminary data, test results were positive for EV-D68 for two (0.08%) of 2,433 patients with ARI who were tested during 2017 and 358 (13.9%) of 2,579 tested during 2018. “
Enterovirus D68–Associated Acute Respiratory Illness — New Vaccine Surveillance Network, United States, July–October, 2017 and 2018
There were a lot more EV D68 infecions in 2018 than there were in 2017
And what does that mean?
Considering that we had “only” 33 confirmed cases of AFM in 16 states in 2017 and at least 223 confirmed cases of AFM in 41 states in 2018, the rise in EV-D68 cases seems to correlate with the rise in AFM.
“Although AFM is rare in the United States, these AFM surveillance data, along with the EV-D68 activity documented through NVSN, provide additional supporting evidence for a temporal association between EV-D68 respiratory illness and AFM. “
Enterovirus D68–Associated Acute Respiratory Illness — New Vaccine Surveillance Network, United States, July–October, 2017 and 2018
Again, few people are going to be surprised by this news…
Although you may just now be hearing about acute flaccid myelitis, it is important to understand that it isn’t new.
The rise in AFM cases began in 2014 and seem to occur every other year.
It wasn’t even new when we started to see an increased number of cases a few years ago.
What is new, is that we are seeing an increased number of cases.
Acute Flaccid Myelitis Timeline
AFM refers to acute (sudden onset) flaccid (droopy or loose muscles) myelitis (inflammation of the spinal cord) and it is a subtype of acute flaccid paralysis.
If that explanation doesn’t really help you, it might help to understand that paralytic polio, like AFM, is another subtype of acute flaccid paralysis.
“In August 2012, the California Department of Public Health (CDPH) was contacted by a San Francisco Bay area clinician who requested poliovirus testing for an unvaccinated man aged 29 years with acute flaccid paralysis (AFP) associated with anterior myelitis (i.e., evidence of inflammation of the spinal cord involving the grey matter including anterior horn cell bodies) and no history of international travel during the month before symptom onset. Within 2 weeks, CDPH had received reports of two additional cases of AFP with anterior myelitis of unknown etiology.”
Acute Flaccid Paralysis with Anterior Myelitis — California, June 2012–June 2014
That seems to be about when this started, in 2012.
Unfortunately, they didn’t figure out what was causing the paralysis in these three patients, despite extensive testing and more cases followed.
“To identify other cases of AFP with anterior myelitis and elucidate possible common etiologies, CDPH posted alerts in official communications for California local health departments during December 2012, July 2013, and February 2014.”
Among 23 cases, California health officials found that the median age of the patients was 10 years old, only two tested positive for EV-D68, although most did have a recent “an upper respiratory or gastrointestinal prodrome.”
“Acute flaccid paralysis (AFP) with anterior myelitis is not a reportable condition, and baseline rates of disease are unknown but are likely quite low. Data from 1992–1998 on children aged <15 years in California indicated an incidence of 1.4 AFP cases per 100,000 children per year and did not identify a single case of AFP with anterior myelitis.”
California wasn’t the only state with cases.
In 2014, there were at least 12 cases in Colorado and 11 in Utah.
“In response to the CDPH and CHCO reports, the CDC established a case definition for enhanced nationwide surveillance of AFM, which included individuals less than 21 years of age with acute flaccid limb weakness and MRI involvement of predominantly the gray matter of the spinal cord without identified etiology presenting after August 1, 2014.”
Messacar et al on Acute Flaccid Myelitis: A Clinical Review of US Cases 2012–2015
All together though, in 2014, once the CDC began actively investigating cases, at least 120 cases were discovered in 34 states. The cases were associated with a large outbreak of EV-D68-associated respiratory illness, although they weren’t able to conclusively link those respiratory illnesses to the AFM cases.
Is there any evidence that there were a lot of cases before 2012?
Or that the CDC has dropped the ball and hasn’t been doing enough to investigate cases?
Not if you look at the timeline.
The CDC was involved very early, called for all cases to be reported, and is actively investigating those cases.
CDC activities include… using multiple research methods to further explore the potential association of AFM with possible causes as well as risk factors for AFM. This includes collaborating with experts to review MRI scans of people from the past 10 years to determine how many AFM cases occurred before 2014, updating treatment and management protocols, and engaging with several academic centers to conduct active surveillance simultaneously for both AFM and respiratory viruses.
CDC on the AFM Investigation
And if the first cases in California and Colorado triggered so much attention, isn’t it likely that any cases anywhere else would have done the same thing?
That makes it very unlikely that many cases were missed in earlier years.
EV-D68 first identified as a cause of respiratory tract infections – 1962
the first reports that EV-D68 could cause severe, even fatal respiratory disease – 2008
first AFM cases are discovered in California – August 2012
the Colorado Department of Public Health and Environment notifies the CDC about a cluster of AFM cases at Children’s Hospital Colorado and a joint investigation begins between the CDPH, CDC, and the physicians caring for the patients – September 2014
the CDC issues a health advisory on Acute Neurologic Illness with Focal Limb Weakness of Unknown Etiology in Children and calls on local and state health departments to report patients to the CDC – September 2014
the CDC conducts a conference call on Neurologic Illness with Limb Weakness in Children, so that clinicians could learn about the latest situation, surveillance, and CDC clinical guidance for AFM testing, patient evaluation and case reporting – October 2014
the CDC posts Interim Considerations for Clinical Management – November 2014
120 AFM cases in 34 states – 2014
Council of State and Territorial Epidemiologists AFM case definition adopted – June 2015
33 AFM cases in 16 states, including one death – 2017
CDC Telebriefing on Acute Flaccid Myelitis in the US with Dr. Nancy Messonnier, director of CDC’s National Center for Immunization and Respiratory Diseases – August 2018
158 AFM cases confirmed in 36 states among 311 reported cases that are being investigated – 2018
The other issue that concerns many parents is why a definitive cause hasn’t yet been identified. And why don’t we have treatments or a cure yet?
“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.”
CDC on AFM Investigation
Although enteroviruses can be difficult to detect in spinal fluid, it is important to keep in mind that isn’t the only thing that is keeping experts from declaring the investigation over and naming a cause, such as EV-D68.
“Among 41 patients whose upper respiratory tract samples were available for enterovirus/rhinovirus testing at CDC, 17 (41%) tested positive: eight (20%) for EV-D68 and nine (22%) for eight other enterovirus/rhinovirus types.”
Eyal Leshem on Notes from the Field: Acute Flaccid Myelitis Among Persons Aged ≤21 Years — United States, August 1–November 13, 2014
Another big issue is that EV-D68 has not been detected in every, or even most AMF patients, and many others have been found to have other enteroviral infections, including EV-A71.
Could it be a coincidence that investigators are finding these enteroviruses simply because it is the season for them to appear? That would mean something else is causing these kids to have AFM.
“During September–November 2016, 10 confirmed cases of AFM were reported in Washington. No common etiology or source of exposure was identified. Enterovirus-A71 was detected in one patient and EV-D68 in two patients, one of whom also tested positive for adenovirus.”
Acute Flaccid Myelitis Among Children — Washington, September–November 2016
While the focus is on EV-D68 as a cause and everyone wants an answer, no one wants the CDC or other investigators to be wrong.
That doesn’t mean that they should be overly cautious and waste time or resources once an answer is evident, but just that they should follow sound epidemiological principles, get the right answer, and help stop kids from getting AFM.
What’s Next for AFM?
There are still a lot of unknowns about AFM, but this is likely what we can expect in the coming months:
the CDC will continue to investigate all unconfirmed cases that have occurred this year, which can take about four weeks after a case is reported and all necessary information is sent in. Keep in mind that since we don’t know if the CDC has already received all of the information on the cases they are investigating, we don’t know when they will finish investigating any pending cases.
local or state health departments will likely reach out to treating physicians to get followup about AFM patients about two months after they developed limb weakness and then report this short-term follow-up data to the CDC. In general, the CDC does not seem to contact patients directly.
From the current investigation, information from outbreaks and cases over the previous years, and cases in other countries, we will hopefully get the answers we need soon to prevent and treat AFM.
The AFM Surveillance Team will participate in a COCA Call in mid-November.
Maybe some of those answers will come during a Clinician Outreach and Communication Activity (COCA) Call on November 13, when members from the CDC Acute Flaccid Myelitis Surveillance Team discuss the “activities the CDC is conducting as part of its investigation into AFM.”
The fact that the CDC has an Acute Flaccid Myelitis Surveillance Team will be news and is hopefully reassuring to some folks…
This is also probably a good time to remind folks that funding for public health has been declining in recent years, even as we expect our public health officials to respond to more things and react more quickly to keep us all safe and healthy. Let’s make sure we fund our public health programs, including the CDC and NIH, so that they have all of the resources they need to address all of today’s public health challenges.
Do we really know whether or not acute flaccid myelitis is contagious or not?
Many people were surprised by a comment by Dr. Robert Redfield, the director of the Centers for Disease Control and Prevention, in an interview for “CBS This Morning,” during which he said that acute flaccid myelitis:
“doesn’t appear to be transmissible from human to human.”
Wait, then how do kids get it?
Is Acute Flaccid Myelitis Contagious?
Since we don’t actually know what causes AFM, it is certainly possible, although rather unlikely, that it is caused by something that is not communicable.
But remember, the leading theory is that AFM is caused by an enteroviral infection, either EV-D68 and EV-A71, as most kids develop symptoms shortly after they had viral symptoms, and these two viruses are most commonly identified.
And you are typically contagious when you are sick with an enteroviral infection.
So how can the CDC Director say that AFM “doesn’t appear to be transmissible from human to human?”
It is because even if the virus that causes AFM is communicable, you can’t actually catch AFM from someone.
Wash your hands to help avoid viral infections. Photo by Andres Chaparro on Pexels.com
Just like polio.
While the polio virus itself is communicable, paralytic polio isn’t. You can’t catch paralytic polio. Instead, you can catch polio, and then you have the small chance that it develops into paralytic polio.
It may not sound like a big difference, but it is.
Just consider what might happen if AFM itself was contagious, and if most of the kids who were exposed to someone with AFM developed AFM themselves…
We would likely see a lot more cases of AFM, especially in clusters in homes, daycare centers, and schools.
Instead, most cases seem to be isolated.
AFM Clusters
But aren’t there reports of clusters of AFM?
“In September 2016, an acute care hospital in Arizona notified the Maricopa County Department of Public Health (MCDPH) of a suspected case of AFM and subsequent cluster of 11 children who were evaluated with similar neurologic deficits; differential diagnoses included transverse myelitis and AFM.”
Notes from the Field: Cluster of Acute Flaccid Myelitis in Five Pediatric Patients — Maricopa County, Arizona, 2016
Yes, kind of.
But they aren’t clusters of epidemiological linked cases.
In Arizona, for example, only four of the 11 children were confirmed to have AFM and “no epidemiologic links were detected among the four patients.”
“In October 2016, Seattle Children’s Hospital notified the Washington State Department of Health (DOH) and CDC of a cluster of acute onset of limb weakness in children aged ≤14 years.”
Acute Flaccid Myelitis Among Children — Washington, September–November 2016
Similarly, at Seattle Children’s Hospital, the ten cases in their “cluster” had nothing in common, except for having prodromal respiratory or gastrointestinal symptoms about seven days before developing AFM symptoms.
It is likely that you see “clusters” at some hospitals simply because they are referral hospitals for a large region.
But even if we don’t know why some kids with these viral infections develop paralysis and other don’t, if they are the cause, then you wouldn’t develop AFM if you never actually had the virus.
“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.”
About Acute Flaccid Myelitis
So handwashing and avoiding others who are sick is still the best strategy to try and avoid getting AFM.
Learn why at least 350 children have developed acute flaccid myelitis since 2014.
Breaking News – 90 cases of AFM in 27 states have been confirmed so far this year, and are among 252 cases that are under investigation.
Polio has been in the news a lot lately.
Well, not exactly polio.
The term “polio-like” has been in the news.
This follows a large outbreak of enterovirus D68 (EV-D68) respiratory infections in 2014, some of which seemed to be associated with the development of acute flaccid myelitis (AFM).
While there were no reports of EV-D68 infections in 2015, there have been “limited sporadic EV-D68 detections in the U.S. in 2016.”
And 2017.
And 2018.
But after we saw 149 cases in 39 states in 2016, there were only 33 cases in 16 states in 2017.
And there have been about 38 cases in 16 states in 2018, coming out of the peak season for AFM cases – August to October.
Polio-Like Syndromes
Similar to coxsackievirus, which causes hand, foot, and mouth disease, EV-D68 is a non-polio enterovirus. On the other hand, the virus that actually causes polio is just a different type of enterovirus.
Because they are all enteroviruses, some get differentiated as being non-polio.
To make it even more confusing, some non-polio enteroviruses can cause a polio-like syndrome.
And both polio and non-polio enteroviruses can cause acute flaccid myelitis.
It is important to note that only some, but not all, of the kids with AFM have been positive for enterovirus D68. In Colorado this year, 9 of 14 cases were linked to EV-A71 infections.
Acute Flaccid Myelitis
What is acute flaccid myelitis?
AFM is a syndrome characterized by sudden onset of limb weakness, sometimes accompanied by cranial nerve dysfunction (such as facial drooping or difficulty speaking). In many cases, distinctive lesions in the gray matter (nerve cells) of the spinal cord may be seen on neuroimaging.
CDC definition
Acute flaccid myelitis caused by the polio virus can usually be recognized because it is associated with an unvaccinated person who traveled to an area that still has cases of polio and who has “one or more limbs with decreased or absent tendon reflexes in the affected limbs, without other apparent cause, and without sensory or cognitive loss. Paralysis usually begins in the arm or leg on one side of the body (asymmetric) and then moves towards the end of the arm or leg (progresses to involve distal muscle groups).”
Since 2014, at least 350 children have developed acute flaccid myelitis. Most had some improvement in function and a small number had a complete recovery, just as a small number had no improvement.
And of course, none of them had polio. In fact, the last polio outbreak in the United States was in 1979.
So maybe we should stop saying “polio-like,” as it likely just confuses people, few people likely know what “polio-like” symptoms actually are, and these cases have nothing to do with the polio virus.
Unfortunately, “despite extensive testing, CDC does not yet know the cause of the AFM cases.”
Still, the CDC recommends standard precautions to try and avoid AFM, including handwashing, avoiding other people who are sick, getting vaccinated (to avoid polio), and protecting your kids from mosquitoes (West Nile virus can cause AFM too).
Polio has been in the news a lot lately.
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