In 2014, a rare, polio-like disease appeared in the United States in 2014, attacking the nervous system of its often young victims – a disease without a clear cause, according to health agencies such as the Centers for Disease Control and Prevention. Now, scientists at the University of California-San Francisco say they have found the most compelling evidence to date that two viruses, closely related to polio, are to blame.
The disease is called acute loose myelitis or AFM. As the name indicates, the victims experience a sudden weakness of their muscles, which can then turn into complete paralysis. This usually affects the hands and feet, but sometimes the facial muscles and throat too. In the most serious cases, paralysis can lead to life-threatening respiratory failure. Other times people are left with neurological symptoms throughout their lives. As of 201
These AFM waves followed a particular pattern with cases occurring every two years as a clockwork. mechanism. In 2018, for example, there are more than 200 reported cases of AFM, but only 22 this year so far.
The symptoms of AFM are not very similar to those caused by the polio virus. But thanks to routine vaccination, polio is almost completely removed from the globe. The suspicion soon turned to poliomyelitis viruses, a group of microbes called enteroviruses that infect us through food, water and air. In particular, two are distinguished: Enterovirus D68, which usually causes common cold symptoms in children, and A71, which can cause arm and leg disease of the rash.
Both D68 and A71 were found in the spinal fluid and intestines of people with AFM and more than 90 percent of victims reported receiving a mild cold before their paralysis began . Studies have also found that strains isolated from human victims of AFM can cause disease in mice similar to AFM . But despite the ongoing investigation, the CDC so far only states that AFM is probably caused by viruses and that these viruses may include D68 and A71 – much to the dismay of some societies health experts and scientists.
One of the most important points about the CDC is that most victims do not show any direct evidence of a virus in their nervous system, let alone an enterovirus, such as viral DNA or RNA. But UCSF scientists say they have found a way to find the hidden traces of D68 and A71 left in AFM patients using a relatively new technology developed by researchers at Harvard Medical School and others called Virscan . Virskan relies on bacteriophages (viruses that hunt bacteria) to look for the antibodies our bodies produce to deal with the viruses. But unlike the older tests, Virskan is able to identify thousands of virus signatures at one time.
In their new study published on Monday in Nature Medicine, the authors used Virscan on spinal fluid samples of 42 children with AFM, as well as control samples taken from 58 children who had other neurological conditions. They found that more than two-thirds of AFM patients had an elevated level of antibodies to enteroviruses in their spinal fluid, but not to another known virus. In contrast, only 7 percent of control patients had enterovirus antibodies. The results were then confirmed by standard antibody testing.
"The strength of this study is not only what is found but what is not found," co-author Joe Derrize, professor of biochemistry and biophysics at UCSF, said in a message  from University.
Even before this new study, scientists pleaded with the CDC to formally blame non-polio viruses as the primary cause of AFM, arguing that the weight of circumstantial evidence was already sufficient to adjudicate. In 2014, for example, the first documented wave of AFM cases was closely preceded by a more serious outbreak of the usual D68 outbreak. And the authors say their latest is "providing additional evidence for the causal role of non-polio EVs in AFM."
Assuming that the CDC ultimately agrees with DeRisi and other experts However, there are still many mysteries to solve for AFM. Something seems to have changed along the way of these viruses to start causing AFM, but we don't know exactly what. We also do not know why only a few people receive AFM, given that enteroviruses often infect people.
But by establishing themselves as the culprit, DeRisi and others hope that it will be easier to start answering their questions and developing a true AFM solution, such as a preventative vaccine.