Thanks to vaccines, polio is a disease that is no longer something that most Americans have to worry about. The highly-infectious virus once meant that children were at risk for paralysis and death whenever outbreaks would occur, but these days, immunization has meant the virus has been eradicated. In recent years though, cases of a rare, polio-like virus called acute flaccid myelitis (AFM) have been on the rise, and it's worrying parents and doctors alike. Is there a cure for AFM? Not only is there no vaccine for AFM, there are also few effective treatment options. In fact, AFM is still not particularly well understood by scientists, according to CNN, which isn't very good news for the 50 people diagnosed with the disease from January to August this year (most of whom where children).

According to CNN, cases of AFM spiked in 2014, when 120 people were diagnosed in 34 states. That number decreased to only 16 cases in 2015, but bounced back up to 50 cases so far this year. Overall, the total number of cases is still low, but given the potentially serious complications that can result from the illness, it's enough to feel pretty scary. AFM is a disease that affects the spinal cord, and, like polio, can lead to paralysis, permanent disability, or even death.

While the cause of AFM is still not known, scientists believe there may be a link between AFM and enterovirus 68, which causes severe respiratory illness. In August 2014, an outbreak of enterovirus 68 was found the be the culprit behind an increased number of children hospitalized for wheezing and breathing difficulty, according to the Centers for Disease Control — around the same time the AFM cases began springing up. As pediatric infectious disease physician and researcher Dr. Kevin Messacar explained to CNN,

What we saw ... [was] that the majority of children had a fever and a respiratory illness. Five days later, they would develop pain in the arms and legs, and weakness followed.

According to CBS News, symptoms of AFM occur suddenly, and can include weakness in the limbs, limping, facial drooping, difficulty swallowing or urinating, slurred speech, or, in severe cases, breathing difficulty. In addition to enterovirus 68, AFM is also thought to be linked to other viral infections (including other enteroviruses and adenoviruses), as well as West Nile virus. A case report in The Lancet in April also suggested a relationship between AFM and the Zika virus, though an official link between the two hasn't been made.

In the absence of a vaccine, or even a more concrete explanation about what's behind the increase of cases, the CDC recommends hand washing as the best defense against AFM. It also suggests that all children be kept up to date on their vaccinations, and that mosquito-control measures be taken to reduce the risk of West Nile virus.

According to TODAY Parents, although the majority of children with AFM do not fully recover, most do improve and regain at least some function. Another important point for parents to consider though? While AFM is certainly concerning, it's also extremely rare. According to CBS News, AFM affects "less than one in a million people," which, while likely not enough to completely alleviate parents' fears, it at least means that AFM probably isn't something they should be overly worried about.