The highly contagious, paralysis-inducing, but preventable virus Poliomyelitis (polio) is rare due to advances that have helped to reduce childhood exposure and increase immunity.

However, a 'polio-like' strain of enterovirus D68, B1, may be the cause behind sudden cases of paralysis affecting children, according to a new study.

The mutated strain of enterovirus D68 was discovered in the respiratory secretion of children in Colorado and California, who suffer from muscle weakness or paralysis for unknown reasons. Lancet Infectious Diseases, a health journal that focuses especially on global health and infectious diseases, recently released a study which addressed the strain and its link to the mystery respiratory illness.

Nationwide, doctors have been reporting the outbreak of unexplained muscle weakness in the arms or legs of children, or complete paralysis, which makes the use of ventilators necessary. While physicians have been quick to identify enterovirus D68 as the cause of this illness, researchers were keen on doing more investigation to determine if physicians were correct in their assessment. In the past, enterovirus D68 was typically only linked to mild issues, such as wheezing or coughing.

Lancet was unable to find definitive link. Concrete confirmation could've only been established if the viral illness was discovered in spinal fluid, and it was not. However, subsequent research did provide the strongest link between enterovirus D68 and paralysis to ever be documented.

Researchers conjectured that the samples were taken too late, which is why the virus was not in the spinal fluid. The children were tested for other parasites, viruses, bacteria and fungi, and no other pathogen capable of causing paralysis was found. It was revealed though the research that the children were infected with B1.

Four years ago, when the B1 strain emerged, it have very few coding differences from past strains of the enterovirus D68 found in the U.S., or another nerve-damaging virus EV-D70. And the mutation of the D68 made the B1 virus much more like polio, said Charles Chiu, an associate professor at the University of California-San Francisco, according to the Washington Post.

According to the 'methods' section of the study, the researchers investigated metagenomic next-generation sequencing, viral genome recovery and enterovirus D68 phylogenetic analysis; and they compared patients with acute flaccid myelitis who were positive for enterovirus D68 with those with acute flaccid myelitis but negative for enterovirus D68. They examined 48 patients: 25 with acute flaccid myelitis, two with enterovirus-associated encephalitis, five with enterovirus D68-associated upper respiratory illness, and 16 with aseptic meningitis or encephalitis who tested positive for enterovirus.

Additionally, the researchers examined siblings with genetically identical strains of the virus. One sibling experienced upper respiratory symptoms, while the other experienced weakness and paralysis.

Researchers from Johns Hopkins and at Children's Hospital Colorado collected DNA from patients from around the nation to better understand outcomes, and to look at genetic and immune response. Scientists determined that each person reacts differently to infectious diseases, so it isn't unusual to see different outcomes in different patients.

The Lancet study additionally unveiled that children affected did not fully recover. After 60 days of data, 70 percent of children experienced minimal to no improvement. Paralysis was decisively permanent or semi-permanent. According to the researcher, this encourages a need for the ongoing surveillance of the virus, particularly while Lancet researchers are unable to predict how the B1 strain of enterovirus D68 will impact the population.

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