Reports of a small number of children having a rare “polio-like syndrome” resulting in partial paralysis are being reported from the United States, Australia, and Asia. These children experience weakness or paralysis in one or more limbs similar to the effects seen with the poliovirus, but do not have the poliovirus. Two of the children are positive for enterovirus-68, a virus associated with symptoms similar to polio. Treatments such as steroids, intravenous immunoglobulin (IvIG), and/or replacement of blood plasma have not made a difference in the childrens’ paralysis.
There are over 60 different types of enteroviruses and enterovirus infection is second only to the common “cold”. Infections most frequently result in mild symptoms such as runny nose, coughing, muscle aches, and sneezing. However, infection with some types of these viruses can result in spontaneous abortion, stillbirth, and congenital anomalies. Even more rarely, infection with certain varieties of enteroviruses damage of tissues including skin, muscles, brain, nerve cells, liver, and the heart. This damage is the result of excessive inflammatory responses of the body in its attempt to rid the body of infection.
Younger individuals, infants, toddlers, children, and adolescents are at greater risk than adults to becoming infected perhaps because the matter of transmission is via feces, sputum, or saliva from an infected person. Transmission of the virus also occurs via the air by coughing or sneezing.
Some enteroviruses specifically target the brain and the nervous system, leading to short or long-term paralysis. For example, polio enteroviruses attack the nervous system triggering an inflammatory response to destroy the viruses. The resulting inflammation can lead to mild paralysis which may disappear on its own (likely after the immune system has eliminated the virus), or to an individual becoming completely paralyzed within hours.
Enteroviruses may persistent in the body for prolonged periods of time with continued inflammation and damage to tissues. Polio patients that initially “recovered” from their disease can continue to experience low-grade inflammatory damage of nerve and muscle cells. Years after their original exposure to the virus, the accumulated affect of this damage may lead to a resurgence of symptoms resulting in a post-polio syndrome (PPS).
Individuals with post-polio syndrome have high levels of inflammatory cytokines, immune factors, in their spinal fluids between the thin layers of tissues that protect the spinal cord. Other conditions resulting from enterovirus infection are often associated with the production of inflammatory molecules. Even patients with relatively mild symptoms and no nervous system complications often have increased blood levels of inflammatory immune factors. This suggests that excessive inflammatory responses are occurring throughout the body.
A delicate balance exists between inflammatory and anti-inflammatory responses of the body. Its ability to maintain immune homeostasis, immune balance is essential. The immune system is always on alert defending itself against infection. However, once the process is triggered, the inflammation must be a measured, controlled response that does not go on to destroy healthy tissue.