Viruses such as the common cold and influenza cannot survive the human's immune response. Other viruses, however, such as herpes, Epstein-Barr, and CMV can survive in our bodies, despite a good immune response.
Enteroviruses are thought to cause self-limited, acute infections, but studies have clearly shown that persistent infections can and do occur.
Enteroviruses do not kill their host cells, our own cells protect them from the immune system's attack. After the immune system fails to kill off the infected cells, it is ineffective in killing the viruses, and unintentionally creating flu-like symptoms.
Most enterovirus infections are acute and self-limited, but in rare cases, they can lead to chronic and persistent infections.
The severity of disease varies from mild symptoms to life threatening conditions.
The following are factors which may contribute to severity of disease:
It has been difficult to demonstrate that Enteroviruses cause chronic diseases without having well documented cases of acute infection. Recent research has demonstrated several cases of acute EV infections that have progressed to chronic EV infections. Years later, Enterovirus protein and RNA could be found in each of the patient's stomachs.