Enteroviruses are included within the family Picornaviridae (pico: small, RNA viruses). They present a capsid of icosahedral symmetry, without envelope; they are small in size (20-30 nm), have single-stranded RNA and positive polarity, so they replicate using their own RNA as a messenger RNA.
More than 70 serotypes are known, including strains of cosacovirus, parechovirus and poliovirus, which cause infections, often clinically inapparent, but which, in a small percentage of cases, lead to serious diseases of the central nervous system, such as aseptic meningitis, encephalomyelitis, cerebellar ataxia, Guillain-Barré syndrome, transverse myelitis and poliomyelitis, among others.
Enteroviral infections are more common in children than in adults. Man is the only known reservoir and transmission is mainly through the fecal-oral and respiratory routes.
Clinical features: The virus enters the body through the oral or nasopharyngeal route, with an incubation period of between 2 and 30-40 days. Many enterovirus infections are stopped by the body's immune defenses, causing few or no symptoms. Some people develop upper respiratory symptoms similar to the common cold. In rare cases, viral pneumonia occurs.
Enteroviruses sometimes survive the immune system's defenses and spread through the bloodstream, causing fever, headache, sore throat, and in some cases vomiting and diarrhoea.
Some strains of enteroviruses also cause a generalized, nonpruritic rash on the skin, or ulcers inside the mouth. This type of disease is the most common enteroviral infection. In very rare cases, the enterovirus evolves from this phase to affect a particular organ and then spreads through the blood to other target tissues, where it replicates.
Severe enterovirus infections (often manifesting as slowly progressive meningoencephalitis, dermatomyositis, and/or hepatitis) occur in patients with defects in B cell function such as chromosome X-linked agammaglobulinemia, but generally do not in individuals with other immunodeficiencies. Aseptic meningitis is more common in children. In infants and young children, the cause is usually Coxsackievirus group A or B, an ECHO virus, or a human Parechovirus.
Diagnosis: Medical evaluation is required to diagnose enterovirus infections. The doctor examines any rash or sore. The laboratory diagnosis, can be made by blood tests or by sending material extracted from the throat, stool or cerebrospinal fluid and perform: Virus culture, detection of viral RNA by RT-PCR and demonstration of seroconversion.
Treatment: There is no cure nor vaccine for enterovirus infections. The purpose of treatment for enterovirus infections is to relieve symptoms. They usually resolve completely, although if they have progressed to infections of the heart or central nervous system, they require hospital admission and special care.