Clinical meaning
Hand, foot, and mouth disease (HFMD) is a common, highly contagious viral illness caused primarily by enteroviruses, most frequently Coxsackievirus A16 (the most common cause in North America and Europe) and Enterovirus 71 (EV-A71, more commonly associated with severe neurological complications in the Asia-Pacific region). Other causative agents include Coxsackievirus A6 (associated with more extensive and atypical rash presentations), Coxsackievirus A10, and other enterovirus serotypes. HFMD predominantly affects children under 5 years of age, with peak incidence between 1 and 3 years, though older children, adolescents, and adults can also be infected. The disease occurs most commonly in summer and early fall in temperate climates but may occur year-round in tropical regions. Transmission occurs through multiple routes: fecal-oral route (the primary mode, through contact with stool from infected individuals), direct contact with vesicular fluid from skin lesions, respiratory droplet spread from oropharyngeal secretions, and contact with contaminated surfaces (fomites). The virus can be shed in stool for weeks to months after clinical recovery, which has important implications for infection control in daycare and household settings. The pathophysiology of HFMD begins with viral entry through the oropharyngeal mucosa or intestinal epithelium. After initial replication in the lymphoid tissue of the pharynx (tonsils) and Peyer patches of the small intestine, the virus enters the bloodstream (primary viremia), disseminates to the reticuloendothelial system (liver, spleen, lymph nodes) for further replication, and then undergoes a second viremic phase (secondary viremia) that distributes the virus to target organs including the oral mucosa, skin of the hands and feet, and in severe cases, the central nervous system. The characteristic oral lesions begin as erythematous macules on the buccal mucosa, tongue, hard palate, and gums that progress to vesicles and then painful shallow ulcers (enanthem). These oral ulcers are the primary cause of odynophagia (painful swallowing) and are the main reason children refuse oral intake, leading to the most common complication of HFMD: dehydration. The skin lesions (exanthem) appear as erythematous macules or papules that may evolve into vesicles on an erythematous base, distributed on the palms, soles, dorsal surfaces of hands and feet, and buttocks (particularly in younger children wearing diapers). The lesions are typically 2 to 8 mm in diameter, oval or football-shaped, and surrounded by a thin halo of erythema. They are usually not pruritic and resolve within 7 to 10 days without scarring. Coxsackievirus A6 can cause a more widespread and atypical presentation with larger vesiculobullous lesions extending to the trunk and extremities, perioral distribution, and subsequent nail changes (onychomadesis or nail shedding occurring 3 to 8 weeks after illness). The most concerning complication of HFMD, particularly when caused by Enterovirus 71, is neurological involvement. EV-A71 has a predilection for the central nervous system and can cause aseptic meningitis, brainstem encephalitis (rhombencephalitis), acute flaccid paralysis (similar to poliomyelitis), and cardiopulmonary failure from neurogenic pulmonary edema. Brainstem encephalitis is the most severe neurological complication and can be rapidly fatal; clinical features include myoclonus (brief involuntary muscle jerks), tremor, ataxia, cranial nerve palsies, and autonomic instability (fluctuating blood pressure and heart rate). The practical nurse must be vigilant for these neurological warning signs, particularly during HFMD outbreaks, as early recognition and supportive care can be lifesaving.