Over the last 18 months, at least 25 children have been affected in the California area by a “polio-like” illness resulting in partial paralysis of five of the children. As of this week, two out of five of these children have tested positive for enterovirus. According to the news media, Australia and Asia have also report similar cases.
A commonly found virus, enteroviruses typically result in only mild symptoms such as runny nose, coughing, muscle aches, and sneezing. However, there are 60 different varieties of enteroviruses, and infection with certain types of these viruses results in spontaneous abortion, stillbirth, and congenital anomalies. Infection with other varieties of enteroviruses can lead to damage of various tissues including skin, muscles, brain, spine, nerve cells, liver, and heart.
Some enteroviruses appear to specifically target the brain and the nervous system, leading to short- or long-term paralysis affecting mobility. So for example, polio enteroviruses attack the nervous system triggering an inflammatory response to destroy the viruses. The resulting inflammation may lead to mild paralysis, or to an individual becoming completely paralyzed within hours.
Some persistent enteroviruses survive in the body for a prolonged time with continued inflammation and damage to tissues. So for example, polio patients that initially recover from their disease may continue to experience damage of nerve and muscle cells by inflammatory processes. This resurgence of symptoms can result in a post-polio syndrome (PPS) years after their original exposure to the virus.
Individuals with post-polio syndrome have high levels of inflammatory cytokines, immune factors, in the 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 may show 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. 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 destroy healthy tissue.