Hand-foot-and-mouth disease pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

HFMD usually affects infants and children, and is quite common. It is highly contagious and is spread through direct contact with the mucus or feces of an infected person. It typically occurs in small epidemics in nursery schools or kindergartens, usually during the summer and autumn months.

Pathophysiology

• HFMD outbreaks typically occur during summer and autumn months in the United states.

Mode of transmission

• HFMD is a contagious disease that is spread from person to person by:

• Close personal contact
• The air (Nasopharyngeal secretions)
• Contact with feces (fecal-oral transmission)
• Contact with contaminated objects and surfaces
• Contaminated water (Swimming pools not properly treated with chlorine)

• The virus can be isolated from the following sources:

• Nose and throat secretions (such as saliva, sputum, or nasal mucus)
• Blister fluid, and
• Feces (stool)

• Following the disease, the infected person (symptomatic or asymptomatic) is most contagious during the first week of illness but can spread disease for days or weeks after symptoms go away.
• Hand, foot, and mouth disease is not transmitted to or from pets or other animals.
• Factors affecting the trasnmission:

• Level of hygeine
• Water quality
• Extent of crowding

Pathogenesis

The exact pathogenesis of EV71 is not fully understood.The pathogenesis of HFMD caused by EV71 includes:

• EV71 replicates in the lymphoid tissues of the oropharyngeal cavity(tonsils), small bowel(payer's patches) and regional lymph nodes(deep cervical and mesenteric nodes) leading to a mild viremia.
• Most of the viruses are destroyed in these lymphatic tissues and the patients remain asymptomatic.
• Patients present with clinical symptoms when the virus disseminates to other organs like reticuloendothelial system(liver, spleen, bone marrow, lymph node), heart, lung, pancreas, skin, mucous membranes and CNS.
• The virus is typically shed for between two and four weeks, and sometimes for as long as 12 weeks post-infection.
• Replication also occurs in the upper respiratory tract and the virus has been recovered from throat swabs for up to two weeks post-infection.

Microscopic pathology

Viruses from the group called enteroviruses cause HFMD (Hand-foot-and-mouth disease). The most common cause is coxsackievirus A16; sometimes, HFMD is caused by enterovirus 71 or other enteroviruses. The enterovirus group includes polioviruses, coxsackieviruses, echoviruses and other enteroviruses.

HFMD begins with a mild fever, poor appetite, malaise ("feeling sick"), and frequently a sore throat. One or 2 days after the fever begins, painful sores develop in the mouth. They begin as small red spots that blister and then often become ulcers. They are usually located on the tongue, gums, and inside of the cheeks. The skin rash develops over 1 to 2 days with flat or raised red spots, some with blisters. The rash does not itch, and it is usually located on the palms of the hands and soles of the feet. It may also appear on the buttocks. A person with HFMD may have only the rash or the mouth ulcers.

HFMD usually affects infants and children, and is quite common. It is highly contagious and is spread through direct contact with the mucus or feces of an infected person. The disease is not spread from pets. Transmission is by direct contact with nose and throat discharges, saliva, fluid from blisters, or stools of an infected person. Most of the transmission occurs in the first week of illness. It typically occurs in small epidemics in nursery schools or kindergartens, usually during the summer and autumn months.

The time between infection and the development of symptoms is about 3 - 7 days.