Enteroviruses

What are the viruses comprising the goup enterovirus?

• coxsackievirus

• echovirus

• poliovirus

In which season do you encounter enterovirus infections?

Enterovirus infections are encountered during late summer and early fall. 

What is the age group most susceptible to enterovirus infections?

The incidence is highest in children less than 1 year old.

What are the common mode of clinical presentation for enterovirus infections?

• Many types of enteroviruses can cause aseptic meningitis. 

• Myocarditis, pericarditis, and pleurodynia are associated with group B coxsackievirus. 

• Polioviruses characteristically cause paralysis (usually asymmetric), but wild type poliovirus has fortunately been eradicated from the Americans. (rare cases of vaccine-associated polio have led to a change to use of IPV prior to OPV in routine childhood immunization schedules). 

• Herpangina (vesicular oral ulcers) and hand-foot-and-mouth disease are classically caused by group A coxsackieviruses. 

• A variety of coxsackieviruses and echoviruses have been associated with benign viral exanthems, mimicking measles or rubella.

What is known about the pathogenesis of the infection?

• Differences in pathogenesis for the enteroviruses mainly result from differences in tissue tropism and cytolytic capacity of the virus.

What is the mode of entry of viruses into humans?

• The upper respiratory tract, the oropharynx, and the intestinal tract are the portals of entry for the enteroviruses. 

Describe their progression after they gain access into humans?

• The virions are impervious to stomach acid, proteases, and bile. 

• The virus initiates replication in the mucosa and lymphoid tissue of the tonsils and pharynx and later infects lymphoid cells of Peyer's patches underlying the intestinal mucosa. 

• Primary viremia spreads the virus to receptor-bearing target tissues, where a second phase of viral replication may occur, resulting in symptoms and a secondary viremia. 

• Virus shedding from the oropharynx can be detected for a short time before symptoms begin, whereas virus production and shedding from the intestine may last for 30 days or longer, even in the presence of a humoral immune response.

• Coxsackieviruses and echoviruses recognize receptors expressed on many cell types and tissues and cause a broad repertoire of disease. 

• These and other enteroviruses recognize receptors on cells of the central nervous system, heart, lung, pancreas, and other tissues.

What is the consequence to target cells?

• Most enteroviruses are cytolytic, replicating rapidly and causing direct damage to the target cell.

What is the human protective mecahnism?

• Antibody is the major protective immune response to the enteroviruses. 

• Secretory antibody can prevent the initial establishment of infection in the oropharynx and gastrointestinal tract, and serum antibody prevents viremic spread to the target tissue and therefore disease. 

• Serum antibody is generally observed 7 to 10 days after infection.

Figure 1. Pathogenesis of enteroviruses. The target tissue infected by the enterovirus determines the predominant disease caused by the virus.

What is the CSF findings with this viral infection?

•  Neutrophil is a common finding in early viral meningitis, but  mononuclear cells predominate later in the disease.

• The  CSF glucose levels are normal 

• CSF viral culture can confirms the diagnosis of viral meningitis.

How is the viral infection detected?

• Viral culture: Yes

• Viral antigen

• Viral antibody

What is the appropriate treatment for this viral infection?

• The management of patients with enteroviral infections includes supportive care. 

• A new drug that inhibits the uncoating of picornavirus particles is being evaluated in clinical trials. 

• Reduces headache

• Reduces duration of illness

What are the infection control measures?

• Patients should be put in enteric isolation. 

• Enteroviruses are transmitted mostly by the fecal-oral route, but some serotypes may be spread by respiratory secretions or fomites.

• Infection control measures are recommended for patients and their families to interrupt transmission of virus to others who may be susceptible. 

• These include handwashing. 

• This is of particular importance in day-care centers, where agents that are spread by the fecal-oral route are of particular concern.