Last Friday, the Minnesota Department of Health (MDH) announced that six Minnesota children, all under the age of 10, had been diagnosed since mid-September with a rare polio-like nervous condition called acute flaccid myelitis (AFM). The condition typically causes sudden muscle weakness or paralysis in the arms or legs, but other symptoms include neck stiffness, facial or eyelid droop, difficulty swallowing and slurred speech.
Experts believe the condition is triggered by a viral infection, although environmental and genetic factors may also be involved.
The condition is quite rare, affecting fewer than 1 in a million people a year. But it has been on the rise since 2014, when an unexpected surge in cases — 120 — was reported, mostly in Colorado and California. Health officials believe those cases were caused by a respiratory virus known as enterovirus D68 (EV-D68).
This year, EV-D68 and another type, enterovirus A71 (EV-A71), have been found in many of the AFM cases. Viruses have not yet been identified in the Minnesota cases.
Minnesota reported three confirmed cases of AFM in 2014. Until this year, the state has seen less than one case per year, even in 2016, when there was another spike in cases nationally (149).
All six of the Minnesota children diagnosed within the past few weeks with the condition were hospitalized. They live in the Twin Cities, central Minnesota and northeastern Minnesota.
Earlier this week, the Centers for Disease Control and Prevention (CDC) released its latest 2018 figures, which showed 38 confirmed cases of AFM across 16 states through Aug. 31. Those numbers don’t include, however, the six Minnesota cases or ones reported elsewhere after that date.
To find out more about AFM, MinnPost spoke with Michael Osterholm, director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota. An edited version of that conversation follows.
MinnPost: What causes AFM?
Michael Osterholm: It’s likely being caused by an infectious agent, much like the polio model. And we think an enterovirus is likely causing it. One — [EV-D68] — has been identified in some cases, but not in the majority of them. It makes sense that an enterovirus would be the cause. If you look at the cases by month of onset, it’s very striking that for each of the months that we’ve had outbreaks you can see the peaks are occurring in August.
MP: Yes, I saw that chart.
MO: That’s actually a very traditional kind of enterovirus-like picture. Most activity tends to peak in that August time period. So it makes sense that it’s an enterovirus. What doesn’t make sense so far is the fact that we’ve had many children for which there has been no [lab confirmation of an enterovirus], even in specimens obtained at a time when we would have thought we should have recovered it. The second thing that is very interesting is that enteroviruses tend to be milder in their disease-causing potential in the youngest population. In this case we have very few adults [getting sick], so it doesn’t really completely fit that picture of enteroviruses.
MP: Do we know why it’s occurring predominantly in young children?
MO: We don’t. And again, remember, the virus isolation cultures are still pending on these six kids from Minnesota. We don’t have one of the kids yet with a positive specimen. So it’s still unclear what is really causing this. It may be that multiple different viruses have filled into this niche.
MP: You said that AFM fits the polio model. That makes it sound kind of frightening. But polio affected so many more people.
MO: Well, there surely were years when many more did get sick. But it would take just literally a couple of cases in the community to shut down schools and to cause community-wide panic before the vaccine was introduced in the 1950s. Today, fortunately, we have not had any [AFM] cases that have needed the kind of classic respiratory support in Minnesota that you often think of in the old days of polio — the “iron lung.” Those days are gone anyway because we don’t use iron lungs with people who have acute flaccid myelitis.
MP: How contagious is AFM?
MO: We don’t know until we know what it is. But enteroviruses in general tend to be fairly infectious.
MP: How concerned should parents be?
MO: I think the risk is really low. Remember, it’s still less than one in a million in terms of individuals. And we don’t want people to change their everyday activities. At the same time, just be prudent. Good hand washing — that’s what we want to really support. That’s the key to prevention.
MP: What symptoms should parents look for, and when should they take their child to a doctor?
MO: That’s important. [Seek medical care] if you start to sense any neck weakness or stiffness in the neck, which could also be signs of meningitis. You start to really get into [AFM’s] clinical symptoms when you get drooping eyelids or facial droop, as well as difficulty swallowing or slurred speech. And, finally, [look for] a weakness in any of the limbs, where it’s just very hard for the individual to move their limbs.
MP: Is there any treatment?
MO: The treatment is supported care. One of the things we learned from polio is that if you quickly identify the cases and, where possible, begin to do aggressive physical therapy, you may actually generate new motor neurons that actually will overcome the impact of the virus on other ones. So very aggressive physical therapy is really important.
MP: What is the prognosis for children with AFM?
MO: So far, many of the kids have recovered — almost fully recovered, if not completely. But unfortunately not all kids have.
MP: And there’s no vaccine, of course, because we don’t yet know what is causing it.
MO: Exactly. One thing I’d like to say, however, is that the public health community, along with the medical community, is doing everything they possibly can right now. Also, when we say that there’s no treatment, that often gives people the sense that it’s hopeless. But first, these kids are largely recovering. It’s not like a life-threatening bacterial infection, where treatment is equated to recovery and no treatment is equated to death. That’s not the case here. Second, there is, in a sense, a treatment. We know that early and aggressive physical therapy intervention can actually be very, very important.
FMI: You can find out more information about AFM at the CDC’s website.