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Minnesota sees recent uptick in acute flaccid myelitis cases
Six children in Minnesota have developed acute flaccid myelitis, or AFM, according to officials from the Minnesota Department of Health. These cases have all occurred since mid-September in children aged younger than 10 years, and all children have been hospitalized, the officials said in a statement.
The CDC reported that certain viruses may trigger this condition or other similar neurologic conditions, including poliovirus or nonpoliovirus, West Nile virus and adenoviruses. Environmental and genetic factors may also be factors contributing to the development of this rare condition.
“[Minnesota Department of Health] investigators are working aggressively with health care providers to gather information about the cases,” the officials said in a statement. “The department is also in contact with the CDC to share information.”
All cases occurred in the Twin Cities, as well as central and northeastern Minnesota.
AFM typically causes muscle weakness in the extremities and may also cause weakness or stiffness in the neck, facial droop or drooping eyelids and difficulty swallowing or slurred speech.
In 2014, three Minnesota children developed AFM during a national uptick in cases. An investigation led disease investigators to believe that these cases were caused by enterovirus D 68. Officials said that Minnesota typically sees less than one case annually.
To prevent AFM, the Department of Health recommends the following precautions for children and parents:
- Frequent hand-washing,
- Proper cough and sneeze etiquette,
- Staying home if ill,
- Making sure all vaccinations are up to date,
- And protecting children from mosquito bites if outside.
“AFM can be diagnosed by examining a person’s nervous system, taking an MRI scan and testing the [cerebrospinal] fluid,” officials from the Minnesota Department of Health said in a statement. “While there is no specific treatment for AFM, doctors may recommend certain interventions on a case-by-case basis.” – by Katherine Bortz
Reference:
CDC: Acute flaccid myelitis - About acute flaccid myelitis. https://www.cdc.gov/acute-flaccid-myelitis/about-afm.html. Accessed: Oct. 8, 2018.
Perspective
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A variety of viruses, including a broad range of enteroviruses, have been identified in patients with AFM. However, there is some difficulty in determining whether the virus found in the secretions of a particular patient is really the cause of his or her paralysis. A 2014 outbreak in the United States was largely associated with Enterovirus 68 (EV68); another enterovirus, EV71, is thought to be responsible for other recent outbreaks. I do not know which virus we are seeing this fall.
EV68 usually causes respiratory illnesses, and it has some characteristics more typical of rhinoviruses than of other enteroviruses. It was only rarely reported until 2008-2010, when it was picked up worldwide by a PCR test meant to detect rhinoviruses in respiratory specimens. EV68 was either not circulating widely before 2008, or it was there but not detected because we normally did not look for enteroviruses in respiratory specimens. There may be more AFM due to EV68 now because there is more virus circulating in the past few years.
Interestingly, there was no uptick in AFM cases associated with the 2008-2010 outbreaks of respiratory illness, suggesting that the virus may have developed more propensity to damage the spinal cord between 2010 and 2014. In the animal model of EV68 disease, the 2014 isolates caused paralysis, but the original respiratory isolate from the 1960s did not. This is consistent with an evolution of the virus toward greater pathogenicity. Therefore, a second potential explanation for more cases may be a genetic change in the circulating strain of the virus.
If it turns out that EV68 or EV71 is a consistent cause of AFM, the best approach for containment would probably be the development of an effective vaccine. There is already a vaccine for EV71 approved for use in China, where an epidemic of hand-foot-mouth disease caused by EV71 was associated with encephalitis and paralytic disease. However, if AFM is associated with a different virus every few years, it will be hard for vaccine developers to hit a moving target.
Reference:
Dyda A, et al. Euro Surveill. 2018;doi:10.2807/1560-7917.ES.2018.23.3.17-00310.