The Centers for Disease Control and Prevention (CDC) still does not know what is causing the growing number of cases of acute flaccid myelitis (AFM) in the United States, but it believes the polio-like illness is not contagious. In a recent interview with CBS, CDC director Robert Redfield, MD said, “The good news is that it doesn’t appear to be transmissible from human to human. We don’t see clustering in families.”1 2
Dr. Redfield’s comments would, at first, appear to minimize the possibility that AFM is caused by a virus or bacterium. Viral and bacterial infections can be spread by people by coughing or sneezing, by touching or shaking hands with other people, or through exchange of bodily fluids such as blood, saliva and semen.3 However, viruses and bacteria can also be spread by other means such as mosquitoes, so it doesn’t mean that such pathogens are being ruled out. In fact, in his interview Redfield went on to say, “Our suspicion is it’s caused by a single agent.”2
The word “agent,” as in infectious agent, is often used to by the scientific community to describe pathogens that cause disease. The book Immunobiology: The Immune System in Health and Disease states: “The agents that cause disease fall into five groups: viruses, bacteria, fungi, protozoa, and helminths (worms).”4
One agent that has been gaining support among physicians as a cause of AFM is a type of virus called an “enterovirus,” specifically Enterovirus D68 (EV-D68) which is considered to be a “distant relative of the poliovirus.”1 According to an article in The Baltimore Sun, neurologist Benjamin Greenberg, MD of UT Southwestern and Children’s Health in Dallas, Texas “suspects” EV-D68 as one of the more likely causes of AFMs.4
Neurologist Kenneth Tyler, MD at the University of Colorado in Aurora believes that the “majority” of AFM cases are linked to EV-D68 and he seems to think the CDC has been “exceedingly cautious” in not coming to the same conclusion.5 Dr. Tyler has criticized the CDC for not moving faster to settle on a cause of AFM. “This is the CDC’s job. This is what they’re supposed to do well. And it’s a source of frustration to many of us that they’re apparently not doing these things,” says Tyler,6 who heads a research laboratory called the Tyler Lab that studies how “viral pathogens interact with the host to produce disease and cellular injury within the brain and spinal cord.”7 The lab is funded by the U.S. National Institutes of Health and the Department of Veterans Affairs.8
Kevin Messacar, MD, who is assistant professor of pediatrics at Children’s Hospital Colorado in Aurora, would like to see the CDC focus on an enterovirus vaccine.5 So would Drs. Greenberg and Tyler, as well as other physicians who feel that if the CDC were to focus on enteroviruses, “it could lead more quickly to a treatment or a vaccine.”9
Despite this growing pressure from some within the medical community, the CDC, thus far at least, is reluctant to attribute the cause of AFM to any one thing, including a virus. The problem with the theory that AFM is caused by an enterovirus, says Nancy Messonnier, MD, director of the CDC’s National Center for Immunization and Respiratory Diseases, is that the virus has not be found in the cerebrospinal fluid of patients with AFM. Dr. Messonnier points out, “AFM is a destructive disease of the neurological system. If this virus was causing this damage, we’d expect to be able to find the virus in the spinal fluid of most of these patients, and we’re not.”9
For now, AFM remains a “mystery.” But it is clear that the CDC, like some of its critics, is becoming frustrated. “I am frustrated that despite all of our efforts we haven’t been able to identify the cause of this mystery illness—we continue to investigate to better understand the clinical picture of AFM cases, risk factors and possible causes of the increase in cases,” says Messonnier, who has said that the CDC has not ruled out environmental toxins or the possibility that AFM could be an autoimmune disease in which the “body’s immune system attacks and destroys body tissue that it mistakes for foreign material.”10 12 13
The CDC has confirmed 72 cases of AFM in 24 states. It is investigating another 119 possible cases. Two weeks ago, the CDC had confirmed 62 cases of AFM in 22 states. In early-October, it had confirmed 38 cases in 16 states.14
1 Vavra K. ‘Polio-like’ illness AFM ‘doesn’t appear to be transmissible,’ CDC director says — but cause remains unknown. The Baltimore Sun Oct. 31, 2018.
2 CDC director says acute flaccid myelitis “doesn’t appear to be transmissible”. CBS News Oct. 29, 2018.
3 Worden J. Viruses and bacteria. NetDoctor.co.uk.
4 Janeway CA, Travers P, Walport M, Shlomchik MJ. Infectious agents and how they cause disease. Immunobiology: The Immune System in Health and Disease. 5th edition.
5 Karlmanga S. Children across U.S. are becoming inexplicably paralyzed. Some parents and experts say federal officials aren’t doing enough. Los Angeles Times Oct. 19, 2018.
6 Ducharme J. Cases of Mysterious Polio-Like Illness Continue to Rise. And Experts Are Frustrated Over a Lack of Answers. TIME Oct. 31, 2018.
7 Tyler Lab. University of Colorado School of Medicine Department of Neurology.
8 Ken Tyler, MD. University of Colorado School of Medicine Department of Neurology.
9 Cohen E. CDC’s handling of polio-like illness criticized by its own advisers. CNN Nov. 2, 2018.
10 Cáceres M. AFM Quickly Go Viral Like Microcephaly? The Vaccine Reaction Oct. 31, 2018.
11 Yong E. The Main Suspect Behind an Ominous Spike in a Polio-Like Illness. The Atlantic Oct. 25, 2018.
12 CDC. About Acute Flaccid Myelitis. CDC.gov.
13 Centers for Disease Control and Prevention. Transcript for CDC Telebriefing: Update on Acute Flaccid Myelitis (AFM) in the U.S. CDC.gov Oct. 17, 2018.
14 Fox M. Why is it so hard to figure out this polio-like illness hitting kids? NBC News Oct 21. 2018.