Hand, Foot, and Mouth Disease (HFMD) is a common viral illness most frequently observed in infants and young children. This contagious infection is caused by viruses belonging to the Enterovirus genus, most often Coxsackievirus A16 and Enterovirus 71. While HFMD is strongly associated with childhood outbreaks, the belief that adults are fully protected is inaccurate. Adults are generally not immune to the viruses that cause HFMD, but they often experience a significantly different clinical course than children.
Immunity Status and Risk for Adults
Many adults believe they are immune because they contracted the illness, perhaps asymptomatically, during childhood. This early exposure creates an immune memory, priming the body to recognize and fight off that specific viral strain upon re-exposure. This mechanism accounts for the reduced frequency of symptomatic infection in the adult population.
However, true, lifelong immunity only develops against the precise strain of the virus that caused the infection. Since HFMD is caused by multiple strains, an individual immune to Coxsackievirus A16 remains susceptible to other circulating strains, such as Coxsackievirus A6. Adults can be reinfected by a different enterovirus, though prior exposure may offer some cross-protection, reducing the severity of subsequent illness.
This susceptibility is relevant in outbreaks involving less common strains, like Coxsackievirus A6, which can cause more severe symptoms in adults. Adults who live or work in close proximity to young children, such as parents and childcare providers, face a higher risk of repeated exposure. Those with compromised immune systems or pregnant individuals are also at a higher risk for more serious outcomes.
How HFMD Presents in Adults
When an adult develops a symptomatic case of HFMD, the experience is often far more debilitating than the mild version seen in children. The illness frequently begins with a high fever, headache, and severe flu-like symptoms, including intense muscle and joint pain. Many adults report a surprising level of physical discomfort and malaise that lasts for several days.
The characteristic rash and sores present uniquely in adults. Painful ulcers, known as herpangina, may form in the mouth and throat, making eating and swallowing extremely difficult. The skin lesions often appear as painful, itchy blisters on the palms of the hands and soles of the feet, sometimes extending to the arms, legs, or torso.
A distinctive delayed symptom is onychomadesis, the painless shedding of fingernails or toenails. This event occurs weeks or even months after the initial infection has resolved. While the acute symptoms typically clear within 7 to 10 days, the lingering physical effects and discomfort can significantly disrupt an adult’s daily life.
Transmission Routes and Prevention Strategies
HFMD is highly contagious and spreads through several primary routes. Adults must be mindful of these routes, especially when caring for sick children. The virus is shed in respiratory droplets when an infected person coughs or sneezes, allowing for aerosol transmission during close contact. Direct contact with an infected person’s blister fluid or saliva can also transmit the virus.
A major route of spread is the fecal-oral pathway, where the virus is shed in the stool for weeks after symptoms disappear. Adults can become infected by touching contaminated surfaces, known as fomites, such as toys, doorknobs, or changing tables, and then touching their own mouth, nose, or eyes. The virus can survive on these common surfaces for extended periods.
Effective prevention relies on meticulous hygiene practices to break these chains of transmission. Rigorous hand washing with soap and water for at least 20 seconds is the most effective measure, particularly after changing diapers, using the restroom, or before preparing food. Frequent disinfection of high-touch surfaces and shared items is also advisable, using a chlorine bleach solution or a recognized disinfectant. Avoiding close contact, such as kissing or sharing utensils, with anyone who is actively symptomatic minimizes exposure risk.