The Polio virus was first isolated in 1908 and is one of the of the most well characterized Enteroviruses. Poliovirus has become a useful model system for understanding the biology of RNA viruses.
Polio is the deadliest strain of all the enteroviruses. It enters through the mouth and multiplies in the throat and gastrointestinal tract. Then polio moves into the bloodstream and is carried to the central nervous system where it replicates and destroys the motor neuron cells. Motor neurons control the muscles for swallowing, circulation, respiration, and the trunk, arms, and legs.
In the United States, the 1952 polio epidemic became the worst outbreak in the nation’s history. Of nearly 58,000 cases reported that year 3,145 died and 21,269 were left with mild to disabling paralysis.
The aim of the WHO was to eradicate polio by the year 2000, however, as of today, this has not been achieved. The virus remains endemic in four countries.
There are two different types of coxsackieviruses: Coxsackie A Viruses (CVA) and Coxsackie B Viruses (CVB). They were discovered in 1948 by Dalldof and Sickles, who isolated the virus in the stool of 2 children from Coxsackie, New York.
Coxsackie A Viruses are generally associated with less clinical syndromes than are group B viruses. CVA cause herpangina (sores in the throat) and hand, foot, and mouth disease.
Coxsackie A Viruses contain 24 strains, where Coxsackie B Viruses contain only 6 strains.
Heart Transplant Patient
Both CVA and CVB can cause meningitis (inflammation of the spinal cord or brain), myocarditis (inflammation of the heart muscle), and pericarditis (inflammation of the sac surrounding the heart).
CVB infections of the cardiac muscle can result in severe complications, including cardiac arrhythmias and acute failure. 30% of the CVB patients may progress to dilated cardiomyopathy (DCM), which accounts for nearly 50,000 hospitalizations and 10,000 deaths each year in the United States.
The only treatment for DCM is a heart transplant and the survival rate is 50% in 5 years.
An ECHO (Enteric Cytopathic Human Orphan) virus belongs to the species Enterovirus B Virus. These viruses were originally not thought to cause disease in humans and were considered "orphan", however, echoviruses can cause infections, so this classification is no longer valid.
Echoviruses are found in the gastrointestinal tract (hence it being part of the enterovirus genus) and exposure to the virus causes other opportunistic infections and diseases.
Although echoviruses originally were classified into 34 serotypes, EV-10 later was reclassified as a reovirus and EV-28 as rhinovirus type 1; echovirus-9 is now considered the same as coxsackie A23.
Conjunctivitis caused by EV70
Numbered Enterovirus - The classification system is unusual, so any new Enterovirus isolated after 1970 is given an Enterovirus number starting with EV68. To this day, Enteroviruses are still being reclassified.
The numbered enteroviruses (Enterovirus types 68 to 71) have not been studied extensively but have been isolated from patients with bronchiolitis, conjunctivitis, meningitis, and paralysis resembling poliomyelitis.
Enterovirus 71 (EV71) was first isolated in California in 1969, and it is a major public health issue across the Asia-Pacific region and beyond.
EV-71 can cause severe neurological diseases, including acute flaccid paralysis, brainstem encephalitis, and acute cardio-pulmonary collapse. EV-71 can even cause death.
The largest outbreak of EV-71 occurred in Taiwan and included 78 fatalities.
Specimens from the cerebrospinal (CSF) may not be optimal for detection of EV-71 by PCR because the sensitivity is poor.
EV PCR of specimens from the respiratory and gastriointestinal tracts had higher diagnostic yields than did EV-PCR of CSF.
EV-71 may be an under-recognized emerging disease in the United States.