Enteroviral infections

What are enteroviral infections?

Enteroviral infections cover a wide range of illnesses that are caused by a group of viruses called enteroviruses (EVs). They are members of the Picornaviridae family which are small, icosahedral, single-stranded, positive-sense RNA viruses.

The most well known of the enteroviruses is the Poliovirus (PV) but this has largely been eradicated. Other enteroviruses are the coxsackie A and B viruses (CVA and CVB) and the echoviruses (Es).

How are enteroviruses classified?

Enteroviruses have been classified into 5 groups based on their molecular properties:

Enterovirus (EV)	Enteroviral illness
Poliovirus PV1-PV3	Polio
Human EV A (HEV-A) CVA2-CVA9, CVA10, CVA12, CVA14, CVA16 EV71	CVAs are the main cause of herpangina and hand-foot-and-mouth disease
Human EV B (HEV-B) CVA9 CVB1-CVB6 E1-E7, E9, E11-E21, E24-E27, E29-E33 EV69	CVBs are associated with epidemic pleurodynia, epidemic myalgia, myocarditis and pericarditis E16 is the cause of Boston exanthema disease E25 and E32 cause eruptive pseudoangiomatosis
Human EV C (HEV-C) CVA1, CVA11, CVA13, CVA15, CVA17-CVA22, CVA24	CVAs are the main cause of herpangina and hand-foot-and-mouth disease
Human EV D (HEV-D) EV68, EV70, EV73-EV75, EV77-EV78	HEV-Ds have been associated with gastrointestinal and respiratory illnesses

Enteroviruses are the cause of many illnesses including the common cold. Some of the coxsackieviruses, echoviruses and EV71 cause a number of skin diseases. Many of the enteroviruses cause exanthems (skin rash or skin eruption as a symptom of a more general disease) or enanthems (rash on the mucous membranes).

Who gets enteroviral infections and how is it spread?

Enteroviral infections are very common and it is estimated that more than one billion people worldwide are affected annually. It appears that people in lower socio-economic groups are more susceptible. In the United States 30,000 to 50,000 hospitalisations each year are due to enteroviral infections.

Enteroviral infections are highly contagious. Enteroviruses spread from person-to-person via oral-oral routes, for example viruses are carried in respiratory droplets when someone sneezes. Other routes are oral-faecal and through direct contact with fluid from skin lesions.

The incubation period for enteroviruses is usually 2-5 days. Once someone is infected the enterovirus implant and replicate in the alimentary tract.

If the infection remains local there is usually no symptoms. However, if the virus passes into the lymphatic system, generalised symptoms of un-wellness may develop. If the virus spreads into the bloodstream then more severe symptoms are experienced.

Enteroviral infections that cause skin reactions

Many enteroviruses cause diseases that have associated skin or mucous membrane reactions. The cutaneous features of some of these diseases are shown in the table below.

Enteroviral infection	Cutaneous features
Herpangina	Lesions develop on the mucous membranes, most often on the tonsils, uvula, and soft palate of the mouth Lesions are characterised by grey-white tiny papulovesicles about 1-2mm in diameter Lesions are self-limiting and resolve over 5-10 days Generalised symptoms include high fever, headache, sore throat, difficulty swallowing, vomiting and abdominal pain
Hand-foot-and-mouth	Oral lesions develop anywhere inside the mouth but most frequently appear on the hard palate, tongue, cheek and gums Oral lesions begin as erythematous macules and papules (flat, inflamed red spots) 2-8mm in diameter. These progress to form thin-walled vesicles (blisters) that burst and form painful ulcers surrounded by a red halo. These heal without treatment over 5-10 days. Skin lesions appear along with or shortly after oral lesions develop. There may be a few lesions or more than 100 lesions and occur on the hands and the feet. Skin lesions begin as erythematous macules or papules which quickly turn into small, grey vesicles surrounded by a red halo. These lesions resolve spontaneously over 7-10 days without scarring.
Boston exanthem disease	After a short fever, pink macules and papules suddenly erupt on the face, trunk, and less commonly the extremities. Small ulcers may also be found on the soft palate and tonsils.
Eruptive pseudoangiomatosis	Lesions, usually no more than 10, develop on the face, trunk and extremities. Lesions are 2-4mm in diameter and red papules resembling cherry angiomas. Lesions resolve spontaneously within 10 days.

Below is a list of other cutaneous features that have been associated with the following enteroviruses.

Cutaneous feature/eruption	Causative enterovirus
Pustular stomatitis with erythema multiforme	CVB5
Widespread vesicular eruption (blisters)	CVA4
Gianotti-Crosti-like eruption	CVA16
Rubelliform eruption (see rubella)	E2
Morbilliform eruption (see measles)	E6, E11, E25
Petechiae (tiny purple spots or purpura)	E11, E19
Punctate macular eruption (tiny flat spots)	E19
Vesicular eruption (blisters)	E11

What is the treatment of enteroviral infections?

Most enteroviral infections heal spontaneously within 7-10 days. Less than 1% of enteroviral infections result in serious symptomatic illness. Cutaneous lesions heal by themselves without scarring.

Treatment is limited to supportive therapy.

• Hydration with plenty of fluids
• Antipyretics such as paracetamol for fever
• Mouth rinses with topical anaesthetics to relieve mouth pain.

Occasionally enteroviruses can causes severe heart and nervous system complications such as myocarditis, aseptic meningitis, meningoencephalitis and paralysis. The antiviral drug pleconaril has shown to be effective treatment in some severe enteroviral infections. This is not yet available in New Zealand (August 2008).