Persistent high fever in hand, foot and mouth disease may signal serious complications: expert

Cases of hand, foot and mouth disease (HFMD) are rising as Korea enters the peak season for the highly contagious childhood illness.

According to the Korea Disease Control and Prevention Agency (KDCA), sentinel surveillance data show that HFMD cases have been increasing since the second half of May. The viral disease typically begins to spread in May, reaches its peak between June and September, and is expected to continue rising in the coming weeks.

HFMD spreads rapidly in group settings such as daycare centers and kindergartens because of its high transmissibility. Professor Yun Ki-wook of the Department of Pediatrics at Seoul National University Hospital (SNUH) explained the disease, its symptoms and key preventive measures.

A: HFMD is caused primarily by enteroviruses, including Coxsackievirus A16 and Enterovirus A71. It most commonly affects children under the age of five, whose immune systems are still developing. The disease is one of the most common summer viral infections, typically emerging in May and peaking in August.

A: Following an incubation period of three to five days, patients usually develop a mild fever, sore throat and loss of appetite. Painful blisters and ulcers then appear on the tongue, palate, gums and inside the lips. In severe cases, mouth pain may make swallowing difficult, causing excessive drooling.

Characteristic red, blister-like rashes also develop on the backs and palms of the hands, the tops and soles of the feet, and the buttocks.

Q: How is HFMD different from chickenpox?

A: HFMD is often mistaken for chickenpox because both illnesses cause skin rashes. However, they are caused by different viruses and present differently.

Chickenpox is caused by the varicella-zoster virus. The rash usually begins on the face or trunk before spreading to the rest of the body. The lesions progress from blisters to pustules and eventually scab over, with itching being a prominent symptom.

A: The virus spreads through direct contact with an infected person's stool, saliva, nasal secretions or sputum, as well as through respiratory droplets produced by coughing or sneezing.

Indirect transmission can also occur through contaminated objects such as toys, playground equipment and doorknobs.

Patients are most contagious during the first week after symptoms appear. However, the virus may continue to be shed in stool for more than eight weeks. For this reason, even after children return to daycare or school, strict hand hygiene remains essential.

A: Most children recover naturally within three to seven days. However, painful mouth sores can reduce food and fluid intake, increasing the risk of dehydration.

If a child refuses to eat, spicy, salty or acidic foods and beverages should be avoided because they can worsen oral pain. Instead, cooled rice porridge, soft foods, milk and yogurt can help relieve discomfort while maintaining hydration.

Medical attention should be sought if a child does not urinate for more than eight hours or shows signs of dehydration, such as producing no tears when crying or having dry lips.

A: Although most cases are mild, rare complications can occur.

Persistent high fever, repeated vomiting, seizures or decreased consciousness may indicate serious complications such as aseptic meningitis, encephalitis or myocarditis. Children showing these warning signs should be taken to an emergency department or evaluated by a physician immediately.

A: There is currently no vaccine or specific antiviral treatment for HFMD. Maintaining good personal hygiene remains the most effective preventive measure.

Parents should encourage children to wash their hands thoroughly with soap and running water after returning home, before and after meals, and after diaper changes. Frequently touched objects, including toys and doorknobs, should also be cleaned regularly.

A: If HFMD is suspected or diagnosed, children should stay home from daycare centers and kindergartens until they are no longer highly contagious. Keeping infected children out of group settings is one of the most effective ways to prevent further transmission.