Hand, Foot, and Mouth Disease Caused by Coxsackievirus A6, Thailand, 2012

Jiratchaya Puenpa, Thaweesak Chieochansin, Piyada Linsuwanon, Sumeth Korkong, Siwanat Thongkomplew, Preyaporn Vichaiwattana, Apiradee Theamboonlers, and Yong Poovorawan

Author affiliations: Chulalongkorn University, Bangkok, Thailand

Abstract

In Thailand, hand, foot, and mouth disease (HFMD) is usually caused by enterovirus 71 or coxsackievirus A16. To determine the cause of a large outbreak of HFMD in Thailand during June–August 2012, we examined patient specimens. Coxsackievirus A6 was the causative agent. To improve prevention and control, causes of HFMD should be monitored.

Coxsackievirus A6 (CAV6) is 1 of 10 genotypes within the family Picornaviridae, genus Enterovirus, species Human enterovirus A. Other genotypes include coxsackievirus A16 (CAV16) and enterovirus 71 (EV71). Although CAV6 is commonly associated with hand, foot, and mouth disease (HFMD) and herpangina (1,2), it has not been of concern until the recent global outbreaks of HFMD (3–6).
In Thailand, the viruses predominately associated with HFMD have been EV71 and CAV16 (7,8); to our knowledge, CAV6 has not been implicated. In 2012, extensive outbreaks of HFMD occurred in Thailand. To determine the pattern, causative agents, and clinical manifestations of HFMD in this 2012 outbreak, we analyzed specimens from patients. This study was approved by the institutional review board of the Faculty of Medicine, Chulalongkorn University; the requirement for written informed consent was waived because the samples were analyzed anonymously.

The Study

In Thailand, HFMD usually occurs during the rainy season (June–August); average incidence during 2007–2011 was 20.2 cases per 100,000 population (9,10). In 2012, an extensive outbreak of HFMD occurred; the incidence rate was 3-fold higher than the average incidence rate of 58.15 cases per 100,000 population or >36.000 cases; the 2012 outbreak included 2 fatal cases of EV71 encephalitis (11). In this outbreak, 2 clinical patterns were observed, and 2 case definitions were applied. Suspected HFMD cases were defined as painful blisters in the oropharynx and blisters on the palms, soles, knees, elbows, and/or buttocks. Suspected herpangina cases were defined as painful blisters in the mouth only, predominantly on the soft palate. Suspected HFMD and herpangina cases were virologically confirmed if samples were positive for viral RNA by nested PCR.