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Enteroviruses are picornaviridae with three serotypic groups:
poliovirus, coxsackievirus and enteric cytopathic human orphan
(ECHO) virus (echovirus). Later isolates have been designated
with a number (e.g. enterovirus 68-72).
Enteroviruses are unenveloped, icosahedral, positive-sense
RNA viruses that encode for four proteins.
- The virus enters cells by a specific receptor that differs for different
virus types, therefore defining tissue tropism.
- The virus is usually acquired via the intestinal tract, causing
subsequent viraemia and invasion of reticuloendothelial cells.
- Secondary viraemia leads to invasion of target organs (e.g.
meninges, spinal cord, brain or myocardium).
- Poliovirus appears to spread along nerve fibres; if significant
multiplication occurs within the dorsal root ganglia, the nerve fibre
may die, with resultant motor paralysis.
- Enteroviruses are spread by the faecal-oral route.
- In developing countries infection occurs early in life; it occurs
later in industrialized countries.
- Infection can occur in parents and carers of infants who have
received the live vaccine.
Polio may present as a minor illness (abortive polio), as aseptic
meningitis (non-paralytic polio), with lower motor neurone
damage and paralysis (paralytic polio), or as a late recrudescence
of muscle wasting that occurs sometimes decades after the initial
paralytic polio (progressive postpoliomyelitis muscle atrophy). In
paralytic polio, muscle involvement is maximal within a few days
after commencement of the paralysis; recovery may occur within
Diagnosis and Treatment
- Aseptic meningitis (see Infections of the central nervous system
) and, rarely, severe focal
encephalitis or general infection may present in neonates.
- Herpangina, a self-limiting, painful, vesicular pharyngeal infection,
is caused by some types of coxsackievirus.
- Coxsackie B causes acute myocarditis (see Endocarditis, myocarditis and pericarditis
- Hand, foot and mouth disease is characterized by a vesicular
rash of the palms, mouth and soles that heals without crusting.
- Diagnosis is usually by nucleic acid amplification test (NAAT)
of CSF, throat swab and faecal specimen.
- Culture is available.
- The multiplicity of serotypes makes serological Diagnosis
- Treatment is supportive care but pleconaril shows benefit in the
treatment of enteroviral meningitis. Artificial ventilation may be
required in the case of polio.
Two vaccines are available: the oral live attenuated Sabin and the
killed parenteral Salk vaccine. Now that polio is limited to a few
countries, the inactivated poliovirus vaccine (IPV) is used.
- Rhinovirus is responsible for the common cold.
- More than 100 serological types exist.
- It has a short incubation period (2-4 days).
- The virus is excreted whilst symptoms are present.
- Transmission is by contact.
The virus infects the upper respiratory tract, invading only the
mucosa and submucosa. The primary symptoms of headache,
nasal discharge, upper respiratory tract inflammation and fever
may be followed by secondary bacterial infections such as otitis
media and sinusitis. Infection occurs worldwide with a peak incidence
occurring in the autumn and winter. Immunity after infection
is poor because of the multiplicity of serotypes. Ruprintrivir
given by nasal spray has been shown to shorten symptoms in clinical
trials. A vaccine is impractical.
Rotaviruses are unenveloped viruses that contain 11 doublestranded
RNA segments coding for nine structural proteins and
several core proteins.
Rotaviruses infect small-intestinal enterocytes; damaged cells are
sloughed into the lumen, releasing viruses. Diarrhoea is caused by
poor sodium and glucose absorption by the immature cells that
replace the damaged enterocytes.
Rotaviruses are the main cause of viral diarrhoea, occurring
usually in children between 6 months and 2 years of age. Morbidity
is highest in the young in developing countries. There are seasonal
peaks in the winter in temperate countries. Antibody to the virus
does not confer immunity to further infection.
Treatment and Prevention
- Diagnosis by reverse transcriptase NAAT is most sensitive.
- Antigen can be detected by enzyme immunoassay (EIA).
- The virus can be visualized by electron microscopy (EM).
Treatment is symptomatic and supportive. The risk of infection
can be reduced by provision of adequate sanitation. Vaccines have
been introduced into countries where rotavirus morbidity and
mortality are high.
Norovirus and astrovirus
Noroviruses are caliciviruses that cause outbreaks of acute diarrhoea
and vomiting in hospitals and care homes, on cruise liners
and in other confined communities. Infection is transmitted by the
faecal-oral and aerosol routes with symptoms developing after a
short incubation period (24-48 h). The viruses can be divided into
five genogroups. Astroviruses are small spherical particles; more
than five serotypes have been recognized.
Virus replication occurs in the mucosal epithelium of the small
intestine, which results in broadening and flattening of the villi and
hyperplasia of crypt cells.
- Infection usually causes a self-limiting, acute diarrhoeal illness.
- It can present with sudden-onset, projectile vomiting and explosive
- Sudden outbreaks of norovirus infection may occur in institutions,
requiring the units to close to new admissions.
- Diagnosis is made by NAAT.
- Sequencing is required for epidemiological purposes and to
monitor the design of future NAAT detection assays.
- Prevention is by isolation, ward closure and good hand-washing