Why do adults get hfmd

Overview

Hand, Foot, and Mouth Disease (HFMD) is a common viral illness that primarily affects infants and children under 5 years old, but can also infect adults. First described in 1957 during an outbreak in Toronto, Canada, HFMD has since been recognized worldwide, with significant epidemics occurring in the Asia-Pacific region. The disease is caused by enteroviruses from the Picornaviridae family, with Coxsackievirus A16 being the most prevalent strain historically. However, since the late 1990s, Enterovirus 71 has emerged as a more virulent strain associated with severe neurological complications. HFMD exhibits seasonal patterns, peaking in summer and early autumn in temperate regions, while occurring year-round in tropical climates. According to the World Health Organization, millions of cases occur annually, with the Western Pacific Region reporting over 1 million cases in 2018 alone. While typically self-limiting, HFMD has significant economic impacts due to school and workplace absences, with outbreaks sometimes closing entire daycare facilities.

How It Works

HFMD transmission occurs through multiple routes: direct contact with infected persons' saliva, fluid from blisters, or feces; respiratory droplets from coughs or sneezes; and contact with contaminated surfaces or objects. The virus enters the body through the mouth or respiratory tract, then replicates in the lymphoid tissues of the throat and intestines. After an incubation period of 3-7 days, the virus spreads through the bloodstream (viremia) to various tissues, particularly the skin and mucous membranes. This leads to the characteristic symptoms: fever, sore throat, and painful sores or blisters on the hands, feet, and inside the mouth. The virus can be shed in stool for several weeks after symptoms resolve, contributing to ongoing transmission. In adults, the immune response is typically more robust than in children, which may explain why symptoms are often milder. However, adults with compromised immune systems or those experiencing their first exposure to a particular enterovirus strain may develop more severe manifestations. The virus can cross the blood-brain barrier in rare cases, leading to neurological complications like aseptic meningitis or encephalitis.

Why It Matters

Understanding adult HFMD infection is crucial for several reasons. First, infected adults can serve as reservoirs for transmission to vulnerable children, particularly in household or childcare settings. Second, while adult cases are generally milder, they can still result in significant workplace absenteeism and economic losses. Healthcare workers, teachers, and parents of young children are at particular risk due to frequent exposure. Third, certain adult populations face elevated risks: pregnant women may transmit the virus to newborns, potentially causing severe neonatal illness, while immunocompromised individuals may experience prolonged or severe disease. The emergence of more virulent strains like Enterovirus 71, which caused large outbreaks in Asia with case fatality rates up to 0.1%, underscores the need for vigilance. Research into vaccines continues, with China approving the world's first EV71 vaccine in 2015, though it doesn't protect against all HFMD-causing viruses. Public health measures emphasizing hand hygiene and surface disinfection remain essential for outbreak control across all age groups.