A polio condition that left more than 100 children behind in the at least partially paralyzed US in 2014 is back, and little is known this time around, officials from the US Centers for Disease Control and Prevention say. The CDC does not exclude any possible triggers – from infections to toxins, autoimmune reactions, to insect bites.
"We could not find a cause for the majority of these cases," said Nancy Messonnier, director of the CDC National Center for Immunization and Respiratory Diseases, said Wednesday at a news conference. "And I'm frustrated that despite all our efforts, we have not been able to identify the cause of this mysterious disease."
But researchers who have studied the muscle-debilitating disease ̵
Scientists at the University of Colorado School of Medicine infected mice with a virus that circulated during the 2014 AFM outbreak as well as during similar spikes of the disease in 2016 and this year. The virus caused a debilitating disease in the mice that looked "very similar to that of children," says Kenneth Tyler, chair of the school's neurology department. Tyler believes that the virus, the enterovirus D68, has changed since its first discovery in 1962 and has become more dangerous. He has bred mice that develop paralysis after infection with the current version of Enterovirus D68, but not from earlier strains. He has tested a number of possible treatments on his mice, but has not yet found any that make a significant difference in the course of their AFM-like illness.
Enterovirus D68 has been associated with some of the human cases of the disease, and although it is not the only cause, it has apparently been a driving force behind the three recent outbreaks, says Kevin Messacar, an infectious disease physician and researcher Children's Hospital Colorado. He and Tyler say the CDC is over-cautious about not recognizing the role of Enterovirus D68 in the disease.
The symptoms of the virus are similar to those of the common cold and may include coughing, shortness of breath and other asthmatic breathing problems. "Many people get the infection and very few will get the neurological disease," which leads to paralysis, says Messacar. In rare cases, about a week after infection, the child develops weakness in his arms, legs or muscles of the face or throat, he says. Although there is no definitive diagnosis, physicians can identify AFM based on a combination of symptoms and an MRI scan that can detect inflammation of the spine.
CDC's Messonier describes AFM as "quite dramatic," saying that the federal agency is making its response worse in previous years. She also stresses that it is extremely rare and affects about one in a million children, so parents should not panic – but they should seek medical help if their child signs of sudden weakness or loss of muscle tone in their arms or Legs shows. Since July, the CDC has confirmed 62 cases of AFM in 22 states and is investigating 65 more possible cases. A child with AFM died last year. Ninety percent of cases have been in children, she says.
Messonnier did not directly treat the D68 enterovirus during the press conference, saying that the CDC has not yet had time to fully analyze the cases of this summer and fall. She said the cases were definitely not caused by the polio virus that was not found in any stool samples from affected children. There is also no evidence of infection by the mosquito-borne West Nile virus, she says, though she still encourages parents to send their kids out with bug spray. Some children with AFM recover fully – usually within a few months – while in others the nerve damage seems permanent, she says.
Mitchel Seruya, a surgeon at the Los Angeles Children's Hospital, said when he operated on children AFM, he was amazed how insensitive their affected nerves are. He could hit her with an electric shock, like touching a car battery, he says, but they do not move. This suggests that the disease can completely obliterate the nerves. Seruya has operated on 15 children whose AFM-induced paralysis lasted at least three months. It redirects redundant nerves from other parts of the arm or abdomen to replace those lost to the disease. He says he had very good results in 14 of the 15 patients; the one girl who did not regain her full function had "a suboptimal result, but [her parents are] happy that she got something back." But treatments for the infection itself remain difficult to access.
Mark Hicar, specialist in pediatric infectious diseases and assistant professor at The University of Buffalo, SUNY, has treated two children with AFM, one in 2014 and one this year. Both were boys – one six, one three; Everyone had a cold-like illness and pricked a fever about a day before they stopped using a leg. No boy was tested positive for Enterovirus D68 or A71, a similar virus also associated with AFM – but the tests are not definitive, he says. The three-year-old improved significantly within the first two days, then rose again and is now being treated with anti-inflammatory drugs in the hospital, Hicar says, hoping the drugs will prevent the boy's immune response from worsening the damage. But the data on the effectiveness of the treatments are so thin that he is not sure if the therapy will help the boy or not.
A vaccine against Enterovirus D68 would be scientifically feasible, but not economical, says Messacar. Polio is a very similar virus – and there is a vaccine that protects against it. The Chinese have developed a vaccine against enterovirus A71, but it is not available in the US, he adds. Because AFM is so rare and has several possible causes, it would be hard for a company to make a vaccine, Messacar says.
The clinical picture is very similar to the polio outbreak of the 1940s and 1950s, says Andrew Pavia, director of the Division of Pediatric Infectious Diseases at the University of Utah, with the exception of his scale. While polio has infected tens of thousands of children, AFM has suffered just over 100 every other year. Many people who had polio and recovered recovered from muscle weakness decades later. It is not clear from mouse studies if AFM symptoms will return in affected individuals Tyler says.
According to the CDC, there were 120 confirmed cases of AFM in the second half of 2014, 22 in 2015, 149 in 2016 and 33 in 2017. "There is an increase in even years that does not seem random," says Messacar, noting that infections are most common in the northern states from July to October, although they are less seasonal south. Research suggests that dew points – a combination of moisture and temperature – affect the transmissibility of the virus, he says.
Pavia agrees to enterovirus D68 is the most likely cause of most AFM cases, but "we have to wait" Whether this year's outbreak follows the same pattern as 2014 and 2016. The primary methods of preventing infection with the virus are the same as with any cold: wash your hands regularly, sneeze in your arm or elbow and try to avoid close contact with people who are sick, says Pavia.
Enterovirus D68 is likely to be contagious for about a week – about as long as the common cold, says Messacar. The disease itself develops toward the end of the infectious period and does not spread from person to person.
That was certainly the case in Sarah Pilarowski's family. Her eight-year-old son Liam got a terrible cold in 2014, but then recovered, but her six-year-old daughter Lydia fell ill and seemed to have a fever, says Pilarowski, a Denver pediatrician. When Lydia was not strong enough to hold an ear in her left hand, Pilarowski worried. Lydia was diagnosed with AFM and endured months of occupational and physical therapy, followed by psychotherapy to resolve her nightmares and ongoing fears. She has not been tested positive for Enterovirus D68, but Pilarowski is convinced that her two children had the virus that made their children sick in the Denver area this summer.
Although there is likely no vaccine or specific treatment In the near future, there are still things that researchers can do to combat AFM, says Messacar, as enterovirus better tracks D68 and A71 infections Experiencing links between the viruses and AFM and understanding the genetic changes in enterovirus D68 to make it more dangerous. "Let's do something about it, let's get some money," he says. "Let's not do that, that's a surprise when it comes back in 2020, but let's be better prepared."