Enterovirus 71 related severe hand, foot and mouth disease outbreaks in South-East Asia: current situation and ongoing challenges

In early 2012, doctors in Cambodia noticed high numbers of infants and young children presenting with a severe and unusual illness. The striking features of the disease were an initial encephalitic presentation followed by a rapidly fatal destructive alveolar pneumonia, alarming experienced clinicians. Between April and July 2012 a total of 78 children were affected, 54 of whom died. Enterovirus 71 (EV71) was identified as the causative organism, possibly aggravated by malnutrition and uncontrolled use of steroids.1 EV71 is one of the pathogens associated with hand, foot and mouth disease (HFMD). It was responsible for large HFMD outbreaks in Taiwan (1.5 million cases) and Malaysia (Sarawak, 2628 cases) in the late 1990s. In 2008 and 2011 large outbreaks were also described in China (490 000 cases) and Vietnam (110 000 cases).2 The recent Cambodian outbreak further demonstrates the emergence and spread of serious EV71 related disease in the South-East Asian region over the last two decades. The clinical syndrome of fever with oral ulcers and exanthema on the hands and feet of young children was first observed in 1957 in New Zealand. The term ‘Hand, foot and mouth disease’ was first used the following year.3 HFMD is mostly caused by EVs belonging to the species Enterovirus A (consisting of Coxsackie viruses A 2–8, 10, 12, 14, 16 and EVs 71, 76 and 89–92). EV71 is thought to have evolved from Coxsackie virus A16 around 1940,4 subsequently diverging into three lineages, A, B and C. Lineages B and C are further divided into five sublineages, with B4, B5, C4 and C5 the dominant sublineages identified in recent years in South-East Asia. Although genetically different, all lineages and sublineages represent one serotype of EV71. HFMD is typically a benign self-limiting illness observed among young children and infants. Outbreaks are often …