Epidemiological and aetiological characteristics of hand, foot, and mouth disease in Shijiazhuang City, Hebei province, China, 2009-2012

Abstract

Large outbreaks of hand, foot, and mouth disease (HFMD) have repeatedly occurred in mainland of China since 2007. In this study, we investigated the epidemiological and aetiological characteristics of HFMD in Shijiazhuang City, one of the biggest northern cities of China. A total of 57,173 clinical HFMD cases, including 911 severe and 32 fatal cases, were reported in Shijiazhuang City during 2009-2012. The disease incidence peaked during March-July, with a small increase in the number of cases observed in November of each year. Seventeen potential HFMD-causing enterovirus serotypes were detected, with the most frequent serotypes being EV-A71 and CV-A16. CV-A10 was also a frequently detected causative serotype, and was associated with the second largest number of severe HFMD cases, following EV-A71. Phylogenetic analysis revealed that all EV-A71, CV-A16 and CV-A10 strains from Shijiazhuang City had co-evolved and co-circulated with those from other Chinese provinces. Our findings underscore the need for enhanced surveillance and molecular detection for HFMD, and suggest that EV-A71 vaccination may be an effective intervention strategy for HFMD prevention and vaccines against CV-A10 and CV-A16 are also urgently needed.

Fig 1. Number of HFMD cases in Shijiazhuang city in 2009 (a), 2010 (b), 2011 (c), and 2012 (d), stratified by age and gender.

Fig 2. Monthly distribution of HFMD cases and enteroviruses detected in Shijiazhuang City, Hebei province of China, 2009–2012.

The number of HFMD cases had apparent seasonal distribution with the peaks in April (year 2009), May (years 2010 and 2012) and June (year 2011), respectively.

Fig 3. The geographic distribution of HFMD cases in Shijiazhuang city, Hebei province of China, 2009–2012.

The epidemic covered all 24 districts of Shijiazhuang City, and annual HFMD incidence rates at the district/county level were indicated in different colours. The maps were generated with MapInfo Pro software (version 16.0, http://www.pitneybowes.com/us/location-intelligence/geographic-information-systems/mapinfo-pro.html).

Fig 4. Monthly distributions and constituent ratio of enterovirus serotypes associated with laboratory-confirmed HFMD cases in Shijiazhuang City, Hebei province of China, 2009–2012.

Fig 5. Phylogenetic tree based on the entire VP1 sequences of the enteroviruses from HFMD cases.

EV-A71, CV-A16, and CV-A10 sequences were omitted in the tree due to large number of the sequences, and sequences of this study were indicated by different colour solid circle in 2009 (red), 2010 (green), 2011 (yellow), and 2012 (blue).

Fig 6. Phylogenetic tree based on the entire VP1 coding region depicting the clustering of (a) EV-A71, (b) CV-A16, and (c) CV-A10 isolated in HFMD cases in Shijiazhuang City, 2009–2012.

The viruses isolated from this study are marked different colour solid circle in 2009 (red), 2010 (green), 2011 (yellow), and 2012 (blue). In addition, the prototype virus is marked in black solid square.