What is Hand, Foot and Mouth Disease?
Hand, Foot and Mouth Disease (HFMD) is an acute infectious disease primarily affecting children under the age of 5. It is characterized by fever and a rash on the hands, feet, and mouth. In most cases, the symptoms are mild, and the prognosis is good. However, in a minority of cases, HFMD can manifest as severe and rapidly progressing, especially when caused by EV71 infection, with a relatively high mortality rate.
Classification of Hand, Foot and Mouth Disease
(1) Common Cases:
Common cases of HFMD typically begin with symptoms of upper respiratory tract infection, such as low-grade fever, cough, runny nose, nausea, and vomiting. Subsequently, rashes appear on the hands, feet, and buttocks, often starting on the palms. Since most affected children have a mild form of the disease with a self-limiting course, clinical management primarily focuses on symptomatic treatment(sources from therapeutique-dermatologique.org).
(2) Severe Cases:
Severe cases of HFMD, often referred to as severe HFMD, are characterized by neurological involvement, respiratory distress, and circulatory dysfunction, with an extremely high mortality rate. Severe cases are more common in children under 3 years of age. Due to the difficulty in recognizing severe cases and their rapidly changing clinical course, it is essential to give them special attention.
Characteristics of Onset
Hand, Foot, and Mouth Disease (HFMD) can occur throughout the year, with the highest incidence typically observed from May to July. It predominantly affects children under the age of 5. The incubation period for HFMD is generally 3-7 days. Most affected children experience a sudden onset of symptoms, with approximately half of them developing a fever 1-2 days before or simultaneously with the appearance of other symptoms. The fever in most cases is low-grade, around 38°C, while severe HFMD can lead to persistent high fever. The majority of severe cases progress rapidly, with severe clinical manifestations appearing within 5 days of illness(quotes from therapeutique-dermatologique.org).
Over 80% of cases are positive for Enterovirus 71 (EV71).
Around 10% are associated with Coxsackie virus Group A.
Currently, in China, most severe cases involving neurological complications are attributed to EV71 and Coxsackie virus Group A. Among these, the majority of fatal cases are associated with EV71. In fact, EV71 is considered one of the most neurotropic enteroviruses, and infected individuals can manifest significant neurological and psychiatric symptoms and signs in a short period.
Characteristics of HFMD Rash
The skin rash in HFMD exhibits distinct features:
(1) Rash Locations: Rashes mainly appear on the hands, feet, mouth, and buttocks.
(2) Order of Rash Onset: Oral mucosal rashes appear relatively early in the disease course, initially presenting as small papules or vesicles with a red halo, primarily affecting the mucous membranes of the tongue and cheeks, which can impact eating.
(3) Rash Characteristics: The rash is neither painful nor itchy, and it does not form scabs or scars. It does not resemble conditions like chickenpox, herpes labialis, or rashes from medications or insect bites.
It’s important to note that not all cases of HFMD will present with rashes in the early stages of the disease. In a study by Yang Sida and others, among 54 fatal cases, only 36 displayed typical rashes, which is much lower than the rash occurrence rate in regular HFMD cases. In other words, some severe HFMD cases may not exhibit rashes or may not have rashes in the early stages of the disease.