Hand, foot and mouth disease (HFMD) is a common viral infection that causes painful sores in the mouth and a rash with small blisters on the hands and feet. A vast majority of the time the disease affects children, though adults may become infected as well.

HFMD is often confused with foot-and-mouth disease, which is a highly infectious viral disease found in farm animals. However, these diseases are not related and are caused by different viruses. In addition, HFMD is not transmitted by animals to humans or vice versa.

Hand, foot and mouth disease is caused by members of a group of viruses known as enteroviruses, which are tiny viruses composed of ribonucleic acid (RNA) and protein. According to the U.S. Centers for Disease Control and Prevention (CDC), the enteroviruses cause an estimated 10 to 15 million or more infections a year in the United States.

HFMD is very contagious and spreads through direct contact with an infected person, usually through unwashed hands or contaminated surfaces or objects (e.g., utensils, telephone). A patient is most contagious during the first week of the illness. However, the infection is generally mild and nearly all patients recover without medical treatment in seven to 10 days.

The most common complication of HFMD is dehydration. The sores in the mouth and throat can make swallowing painful and difficult, causing some patients not to consume the necessary fluids. In addition, HFMD may pose some complications during the first three months (the first trimester) of pregnancy. Pregnant patients who develop the disease shortly before delivery are at risk for passing the virus to the newborn. Although most newborns with HFMD have mild symptoms, in rare cases they may develop a severe life-threatening infection involving many organ systems, including the heart and liver.

Other complications of HFMD are rare and may include:

• Aseptic meningitis. An infection resulting in inflammation of the membranes (meninges) and cerebrospinal fluid surrounding the brain and spinal cord. Aseptic or viral meningitis is usually mild and often resolves on its own in about 10 days.
  
  
• Pneumonia. Inflammation of the lungs caused by infection with a virus.
  
  
• Myocarditis. A rare viral infection resulting in inflammation of the heart.
  
  
• Encephalitis. A severe and potentially life-threatening disease that involves brain inflammation caused by a virus.

Prevalence of HFMD is seasonal in temperate climates, with outbreaks usually occurring in the summer and fall. In tropical climates, the disease occurs during all seasons. In recent years, major outbreaks of the viral infection with severe complications were reported in Malaysia and Taiwan.