Table of Contents Author Guidelines Submit a Manuscript
Canadian Journal of Infectious Diseases and Medical Microbiology
Volume 2018, Article ID 2751457, 12 pages
https://doi.org/10.1155/2018/2751457
Review Article

The Risk Factors of Acquiring Severe Hand, Foot, and Mouth Disease: A Meta-Analysis

1Department of Epidemiology, China Medical University, Shenyang, Liaoning 110000, China
2Department of Infectious Disease, Shenyang Center for Disease Control and Prevention, Shenyang, Liaoning 110031, China

Correspondence should be addressed to Bao Sen Zhou; nc.ude.umc@uohzsb

Received 5 February 2018; Accepted 22 April 2018; Published 26 June 2018

Academic Editor: Pascal Thibon

Copyright © 2018 Bai Jun Sun et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objectives. The incidence of severe hand, foot, and mouth disease (HFMD) is not low, especially in mainland China in almost every year recently. In this study, we conducted a meta-analysis to generate large-scale evidence on the risk factors of severe HFMD to provide suggestions on prevention and controlling. Methods. PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), and Wanfang (Chinese) were searched to identify relevant articles. All analyses were performed using Stata 14.0. Results. We conducted a meta-analysis of 11 separate studies. Fever (odds ratio (OR) 7.396, 95% confidence interval (CI) 3.565–15.342), fever for more than 3 days (OR 5.773, 95% CI 4.199–7.939), vomiting (OR 6.023, 95% CI 2.598–13.963), limb trembling (OR 42.348, 95% CI 11.765–152.437), dyspnea (OR 12.869, 95% CI 1.948–85.017), contact with HFMD children (OR 5.326, 95% CI 1.263–22.466), rashes on the hips (OR 1.650, 95% CI 1.303–2.090), pathologic reflexes (OR 3057.064, 95% CI 494.409–19000), Lethargy (OR 31.791, 95% CI 3.369–300.020), convulsions (OR 23.652, 95% CI 1.973–283.592), and EV71 infection (OR 9.056, 95% CI 4.102–19.996) were significantly related to the risk of severe HFMD. We did not find an association between female sex (OR 0.918, 95% CI 0.738–1.142), scatter-lived children (OR 1.347, 95% CI 0.245–7.397), floating population (OR 0.847, 95% CI 0.202–3.549), rash on the hands (OR 0.740, 95% CI 0.292–1.874), rash on the foot (OR 0.905, 95% CI 0.645–1.272), the level of the clinic visited first (below the country level) (OR 5.276, 95% CI 0.781–35.630), breast feeding (OR 0.523, 95% CI 0.167–1.643), and the risk of severe HFMD. Conclusions. Fever, fever for more than 3 days, vomiting, limb trembling, dyspnea, contact with HFMD children, rashes on the hips, pathologic reflexes, lethargy, convulsions, and EV71 infection are risk factors for severe HFMD.

1. Introduction

Hand, foot, and mouth disease (HFMD) is a common childhood infection disease with characteristic features of fever, oral ulcers, and vesicular rashes on the hands, feet, and buttocks. It is caused by a group of enteroviruses, commonly coxsackie A16 and enterovirus-71 (EV-71). The mode of transmission of HFMD is mainly via the fecal-oral route, respiratory droplets, contact with blister fluid of an infected individual, or general close contact with infected individuals. Most HFMD cases were mild and limited to fever and vesicular exanthema on patients’ palms, soles, and mouth along with discomfortness at certain levels. However, some severe cases with potentially fatal complications such as brain stem encephalitis (BE) and/or pulmonary edema (PE) show rapid progression that may lead to serious sequelae, even death. In recent years, more and more outbreaks of severe cases have been reported [1, 2]. Previous studies have shown that close monitoring and timely intervention may prevent the development of severity and avert the death of severe HFMD [35]. Therefore, it is extremely necessary to identify the risk factors which predict the occurrence of severity. Meta-analysis is a means of increasing the effective sample size under investigation through pooling of data from individual association studies, thus enhancing the statistical power [6]. In order to identify risk factors of acquiring severe HFMD, prevent deterioration, and reduce acute mortality, we conducted this meta-analysis to determine the risk factors for severe HFMD.

2. Materials and Methods

2.1. Study Selection

A systematic search of the literature was done in the following electronic databases: PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), and Wanfang (Chinese). The following keywords were used: severe hand foot mouth disease (HFMD), risk factors, and case control study. The quality of the included studies was assessed using the Newcastle-Ottawa Scale, and studies achieving six or more points were considered to be of high quality.

2.2. Inclusion and Exclusion Criteria

Two investigators searched the electronic databases independently according to the following criteria for inclusion: (1) a case-control study including severe and mild disease patient groups; (2) published up to June 2017; (3) diagnosis of severe HFMD and mild HFMD consistent with the criteria defined by us. Abstracts, reviews, case reports, noncomparative studies, and low-quality studies were excluded. In cases of disagreement, a third investigator acted as an arbitrator, and the disagreements were resolved with the research team by discussion.

2.3. Data Extraction and Quality Assessment

The following items were extracted from the included studies: the first author’s name, year of publication, source of publication, type of the study, risk factors, total sample size, number of severe and mild HFMD cases, and diagnostic criteria for severe and mild HFMD.

The publication bias was evaluated using Egger’s test [7]. If , the publication bias exists; otherwise, the publication bias does not exist.

2.4. Definitions

HFMD cases were divided into two groups according to Guidelines on the Diagnosis and Treatment of HFMD [8]. The mild HFMD was defined as papular/vesicular skin rashes on the hand, foot, mouth, or buttock, and the severe HFMD was defined as mild HFMD with the addition of neurological, respiratory, or circulatory complications, or death. Neurological complications included aseptic meningitis, encephalitis, and acute flaccid paralysis [9]. The duration of fever was defined as body temperature ≥37.5°C.

2.5. Meta-Analysis Methods

Stata 14.0 was used for the statistical analysis. The odds ratio (OR) and 95% confidence intervals (CI) were calculated using the fixed effect model or random effect model, and the choice for statistical model was determined by their heterogeneity which were assessed by the X2 and I2 statistics. I2 >50% and X2-statistic () were considered to show significant heterogeneity, and the random effect model was adopted; otherwise, the fixed effect model was used. The OR and 95% CI were used as summary statistics for the comparison of the following risk factors: fever, fever for more than 3 days, vomiting, limb trembling, dyspnea, contact with HFMD children, rashes on the hips, pathologic reflexes, lethargy, convulsions, EV71 infection, female sex, scatter-lived children, floating population, rash on the hands, rash on the foot, the level of the clinic visited first (below the country level), and breast feeding.

The pooled estimate of risk was obtained by the Mantel–Haenszel method in the fixed effect model and by the M-H heterogeneity method in the random effect model. All values were 2-sided. A value less than 0.05 was considered to be statistically significant.

3. Results

3.1. Characteristics of Included Studies

The first search strategy generated 109 studies. Only 11 articles [1020] met the inclusion criteria, and they were all carried out in China. The selection process is shown in Figure 1. All the studies were of high quality according to the Newcastle-Ottawa Scale (NOS). The sample sizes of the included studies ranged from 76 to 761 and amounted to 4082 subjects in total. There were 1640 patients in the severe HFMD group and 2442 patients in the mild HFMD group. The study and patients’ characteristics are summarized in Table 1. The two groups were similar with regard to age and gender.

Figure 1: Flow chart showing the selection process for the meta-analysis.
Table 1: Characteristics of the included studies and patients into meta-analysis.
3.2. Risk Factors of Severe HFMD
3.2.1. Patient Clinical Manifestations

In 8 studies, fever was strongly related to the risk of severe HFMD (OR 7.396, 95% CI 3.565–15.342). In 3 studies, fever for more than 3 days was significantly associated with severe HFMD (OR 5.773, 95% CI 4.199–7.939). In 3 studies, rashes on the hips or buttocks were significantly associated with severe HFMD (OR 1.650, 95% CI 1.303–2.090). However, we found no significant association between rash on the palm, rash on the soles, and severe HFMD in 3 studies, respectively (OR 0.740, 95% CI 0.292–1.874 and OR 0.905 95% CI 0.645–1.272) (Table 2; Figures 26).

Table 2: Meta-analysis of risk factors for the hand, foot, and mouth disease in 18 separate studies.
Figure 2: Forest plots showing the results of the meta-analysis regarding fever.
Figure 3: Forest plots showing the results of the meta-analysis regarding fever for more than 3 days.
Figure 4: Forest plots showing the results of the meta-analysis regarding rash on the hands.
Figure 5: Forest plots showing the results of the meta-analysis regarding rash on the foot.
Figure 6: Forest plots showing the results of the meta-analysis regarding rashes on the hips.

We found that vomiting (OR 6.023, 95% CI 2.598–13.963), limb trembling (OR 42.348, 95% CI 11.765–152.437), dyspnea (OR 12.869, 95% CI 1.948–85.017), pathologic reflexes (OR 3057.064, 95% CI 494.409–19000), lethargy (OR 31.791, 95% CI 3.369–300.020), and convulsions (OR 23.652, 95% CI 1.973–283.592) were significantly associated with severe HFMD (Table 2; Figures 712).

Figure 7: Forest plots showing the results of the meta-analysis regarding vomiting.
Figure 8: Forest plots showing the results of the meta-analysis regarding limb trembling.
Figure 9: Forest plots showing the results of the meta-analysis regarding dyspnea.
Figure 10: Forest plots showing the results of the meta-analysis regarding pathologic reflexes.
Figure 11: Forest plots showing the results of the meta-analysis regarding lethargy.
Figure 12: Forest plots showing the results of the meta-analysis regarding convulsions.
3.2.2. Patient Demographic Characteristics

We analyzed the association between demographic characteristics of patients and severe HFMD and found that female gender (OR 1.06, 95% CI 0.91–1.24), scatter-lived children (OR 1.06, 95% CI 0.91–1.24), and floating population (OR 1.06, 95% CI 0.91–1.24) were all not related to the risk of severe HFMD (Table 2; Figures 1315).

Figure 13: Forest plots showing the results of the meta-analysis regarding female gender.
Figure 14: Forest plots showing the results of the meta-analysis regarding scatter-lived children.
Figure 15: Forest plots showing the results of the meta-analysis regarding floating population.
3.2.3. EV71 Infection

Seven studies analyzed the association between EV71 infection and severe HFMD, and the results suggest that EV71 infection significantly increased the probability of severe HFMD (OR 9.056, 95% CI 4.102–19.996) (Table 2; Figure 16).

Figure 16: Forest plots showing the results of the meta-analysis regarding EV71 infection.
3.2.4. Association between Other Factors and Severe HFMD

Seven studies suggest that contacting with HFMD children significantly increased the risk of severe HFMD (OR 5.326, 95% CI 1.263–22.466). We found no association between the level of the clinic visited first (below the country level) (OR 5.276, 95% CI 0.781–35.630), breast feeding (OR 0.523, 95% CI 0.167–1.643), and severe HFMD (Table 2; Figures 1719).

Figure 17: Forest plots showing the results of the meta-analysis regarding contact with HFMD children.
Figure 18: Forest plots showing the results of the meta-analysis regarding the level of the clinic visited first (below the country level).
Figure 19: Forest plots showing the results of the meta-analysis regarding breast feeding.
3.3. Evaluation of Publication Bias

Egger’s test analysis of total complications was performed. The results are shown in Table 3. Seventeen compared factors had no publication bias; one risk factor did (rashes on the hips).

Table 3: Egger’s test of all risk factors.

4. Discussion

A recent meta-analysis involving 19 separate studies [21] found that clinical characteristics such as duration of fever more than 3 days, body temperature ≥37.5°C, lethargy, vomiting, and EV71 infection were significantly related to the risk of severe HFMD which is consistent with our findings. Other than these risk factors, we also found rashes on the hips or buttocks, limb trembling, dyspnea, pathologic reflexes, convulsions, and contact with HFMD children significantly increased the risk of severe HFMD. However, we found no significant association between rash on the palm, rash on the soles, female gender, scatter-lived children, floating population, the level of the clinic visited first (below the country level), breast feeding, and severe HFMD.

Previous studies on gender have different conclusions: Pan et al. [12] thought that female have a lower risk of attacking severe HFMD than male; however, Wang et al. [10], Yang et al. [11], and Liu et al. [13] do not think that there is a connection, and our analysis found that there is no association between gender and severe HFMD.

Both male and female have the same opportunities to develop severe HFMD. Previous studies have also drawn different conclusions regarding scatter-lived children and floating populations: Zhang et al. [15] thought that scatter-lived children reduce the risk of acquiring severe HFMD, but Wang et al. [10], Yang et al. [11], and Pan et al. [12] got the opposite conclusion. Zhang et al. [15] thought that floating children have a lower risk of acquiring severe HFMD; however, Zeng et al. [14] found a higher risk between them. Yang et al. [11] and Pan et al. [12] did not find any association. Our analysis found both scatter-lived children and floating populations is not related to the risk of severe HFMD.

Oral ulcers and vesicular rashes on the hands, feet, and hip/buttocks are common signs of HFMD; however, rashes on different parts can lead to different levels of severity of HFMD. Previous studies regarding rashes on the hands and rashes on the hips have different conclusions: Yang et al. [11] thought that rashes on the hands are protective factors of HFMD, and other two studies found no association between them; Zhang et al. [15] thought that rashes on the hips are risk factors of HFMD, and other two studies found no association between them. Our studies confirm previous conclusions about the relationship between rashes on the feet and severe HFMD but found there is no association between rashes on the hands and severe HFMD and also found that rashes on the hips are risk factors. These remind us to pay close attention to those kinds of patients whose rashes on the hips.

Most of previous studies included in our meta-analysis found that fever, vomiting, lethargy, convulsions, and contact with HFMD children are risk factors of severe HFMD, and our study confirmed it. Our study also confirmed that severe HFMD is associated with fever for more than 3 days, limb trembling/shaking, dyspnea, pathologic reflexes, and EV71 infection again. Any of these factors increase the possibility of developing severe HFMD. Therefore, early recognition and meticulous management of patients with these risk factors are required [22, 23].

EV71 invades the central nervous system causing severe disease ranging from meningitis to fatal encephalitis [24]. In our study, we retrieved 7 studies that analyzed the association between EV71 infection and severe HFMD, and the meta-analysis showed that EV71 infection was significantly associated with the development of severe HFMD. Enterovirus 71 (EV71) is the key pathogen of HFMD, accounting for 70% severe HFMD cases and 90% HFMD-related deaths [25] Therefore, EV71 vaccine development is very important in preventing severe HFMD epidemics. On December 3, 2015, the China Food and Drug Administration (CFDA) approved the first inactivated enterovirus 71 (EV71) whole virus vaccine for preventing severe hand, foot, and mouth disease (HFMD) [26]. In Mainland China, phase III clinical trials showed that all three EV71 vaccines had good safety and protective efficacy in infants. The protection rates against the EV71-caused HFMD were 97.4%, 94.8%, and 90.0%, respectively, following EV71 vaccination [2729]. HFMD has become a serious public health issue over the past decades in the Asia-Pacific countries [9]. Inactivated EV71 vaccine will be a valuable tool in protecting children’s health in Mainland China and other countries with high HFMD prevalence.

In recent years, coxsackievirus A6 (CV-A6) has caused widespread concern around the world and has gradually emerged as a major pathogen of the hand-foot-mouth disease (HFMD) [30]. The infection caused by CV-A6 is more likely to present with atypical clinical symptoms compared with that by EV-A71 (enterovirus 71, EV-A71) and CV-A16 (coxsackievirus A16, CV-A16) [31], and detoxification is a common clinical manifestation of HFMD caused by CV-A6 [32]. In severe cases, neurological symptoms, aseptic meningitis, and encephalitis occur [33]. However, the current researches on Cox A6 are not comprehensive, and there is a lack of a case-control study on the risk factors of CV-A6. Therefore, more research is needed on coxsackie A6.

Liu et al. [13] reported that the level of the clinic visited first (below the country level) has a marked impact on severe HFMD development. However, our study did not come to the same conclusion. In addition, Zhang et al. [15] found breast feeding is a protective factor. However, our study did not produce the same results also. There may be less to do with the number of studies being included and the less number of samples. Therefore, further studies are needed to be conducted to confirm the association between the level of the clinic visited first and severe HFMD as well as the association between breast feeding and severe HFMD.

5. Conclusions

In conclusion, we found that eleven factors are associated with the severity of HFMD. Previous conclusion regarding the association between fever (body temperature ≥37.5°C), fever more than 3 days, lethargy, vomiting, and EV71 infection and severe HFMD was consistent with our findings. Also, we found rashes on the hips or buttocks, limb trembling/shaking, dyspnea/breathlessness, pathologic reflexes, convulsions/twitch, and contact with HFMD children significantly increased the risk of severe HFMD. But, we found no significant association between rashes on the palm, rashes on the soles, female gender, scatter-lived children, floating population/migrant, the level of the clinic visited first (below the country level), breast feeding, and severe HFMD. Further studies are needed to confirm our findings.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

The authors thank Professor Bao Sen Zhou for the valuable advice and critical reading of the manuscript.

References

  1. N. T. B. Nguyen, H. V. Pham, C. Q. Hoang et al., “Epidemiological and clinical characteristics of children who died from hand, foot and mouth disease in Vietnam 2011,” BMC Infectious Diseases, vol. 14, no. 1, p. 341, 2014. View at Publisher · View at Google Scholar · View at Scopus
  2. C. Y. Chong, K. P. Chan, V. A. Shah et al., “Hand, foot and mouth disease in Singapore: a comparison of fatal and non-fatal cases,” Acta Paediatrica, vol. 92, no. 10, pp. 1163–1169, 2003. View at Publisher · View at Google Scholar · View at Scopus
  3. L. Y. Chang, S. H. Hsia, C. T. Wu et al., “Outcome of enterovirus 71 infections with or without stage-based management: 1998 to 2002,” Pediatric Infectious Disease Journal, vol. 23, no. 4, pp. 327–332, 2004. View at Publisher · View at Google Scholar · View at Scopus
  4. M. H. Ooi, S. C. Wong, A. Mohan et al., “Identification and validation of clinical predictors for the risk of neurological involvement in children with hand, foot, and mouth disease in Sarawak,” BMC Infectious Diseases, vol. 9, p. 3, 2009. View at Publisher · View at Google Scholar · View at Scopus
  5. J. N. Wang, C. T. Yao, C. N. Yeh et al., “Critical management in patients with severe enterovirus71 infection,” Pediatrics International, vol. 48, no. 3, pp. 250–256, 2006. View at Publisher · View at Google Scholar · View at Scopus
  6. M. Egger, G. D. Smith, M. Schneider, and C. Minder, “Bias in meta-analysis detected by a simple graphical test,” BMJ, vol. 315, pp. 629–634, 1997. View at Publisher · View at Google Scholar
  7. C. B. Begg and M. Mazumdar, “Operating characteristics of a rank correlation test for publication bias,” Biometrics, vol. 50, no. 4, pp. 1088–1101, 1994. View at Publisher · View at Google Scholar · View at Scopus
  8. Ministry of Health of the People’s Republic of China, “Guidelines on the diagnosis and treatment of hand, foot, and mouth disease,” in International Journal of Respiration, vol. 30, no. 24, pp. 1473–1475, 2010. View at Google Scholar
  9. World Health Organization, A Guide to Clinical Management and Public Health Response for Hand, Foot and Mouth Disease (HFMD), WHO, Geneva, Switzerland, November 2013, http://www.wpro.who.int/emerging_diseases/documents/HFMD Guidance/en/index.html.
  10. Q. Wang, W. Zhang, Y. Zhang et al., “Clinical features of severe cases of hand, foot and mouth disease with EV71 virus infection in China,” Archives of Medical Science, vol. 10, no. 3, pp. 510–516, 2014. View at Publisher · View at Google Scholar · View at Scopus
  11. T. C. Yang, G. Z. Xu, H. J. Dong et al., “A case–control study of risk factors for severe hand-foot-mouth disease among children in Ningbo, China, 2010-2011,” European Journal of Pediatrics, vol. 171, no. 9, pp. 1359–1364, 2012. View at Google Scholar
  12. H. Pan, Y. X. Zheng, S. H. Mao et al., “A case-control study on risk factors that associated with severe hand-foot-mouth disease in Shanghai,” Chinese Journal of Epidemiology, vol. 33, no. 8, pp. 763–767, 2012. View at Google Scholar
  13. Z. Liu, S. K. Wang, R. Yang, and X. Ou, “A case-control study of risk factors for severe hand-foot-mouth disease in Yuxi, China, 2010-2012,” Virologica Sinica, vol. 29, no. 2, pp. 123–125, 2014. View at Publisher · View at Google Scholar · View at Scopus
  14. M. Zeng, D. Pu, X. Mo et al., “Children of rural-to-urban migrant workers in China are at a higher risk of contracting severe hand, foot and mouth disease and EV71 infection: a hospital-based study,” Emerging Microbes & Infections, vol. 2, no. 10, p. e72, 2013. View at Publisher · View at Google Scholar
  15. D. M. Zhang, R. L. Li, W. J. Zhang et al., “A case-control study on risk factors for severe hand, foot and mouth disease,” Scientific Reports, vol. 7, Article ID 40282, 2017. View at Publisher · View at Google Scholar · View at Scopus
  16. H. L. Deng, Y. F. Zhang, Y. P. Li et al., “N-terminal pro-brain natriuretic peptide levels associated with severe hand, foot and mouth disease,” BMC Infectious Diseases, vol. 16, no. 1, p. 585, 2016. View at Publisher · View at Google Scholar · View at Scopus
  17. Y. P. Li, S. S. Dang, H. L. Deng et al., “Breastfeeding, previous Epstein-Barr virus infection, enterovirus 71 infection, and rural residence are associated with the severity of hand, foot, and mouth disease,” European Journal of Pediatrics, vol. 172, no. 5, pp. 661–666, 2013. View at Publisher · View at Google Scholar · View at Scopus
  18. J. Pan, M. Chen, X. Zhang, Y. Chen, H. Liu, and W. Shen, “High risk factors for severe hand, foot and mouth disease: a multicenter retrospective survey in Anhui Province China, 2008-2009,” Indian Journal of Dermatology, vol. 57, no. 4, pp. 316–321, 2012. View at Publisher · View at Google Scholar · View at Scopus
  19. T. Luo, D. H. Shi, M. W. Deng et al., “Analysis of epidemiological characteristics of severe HFMD in South of QianDong area in 2014,” Journal of Applied Preventive Medicine, vol. 22, no. 6, pp. 506–508, 2016. View at Google Scholar
  20. H. C. Li, “Clinical observation and risk factors of children with severe HFMD,” Chinese and Foreign Medical Research, vol. 14, no. 8, pp. 31-32, 2016. View at Google Scholar
  21. Y. R. Fang, S. P. Wang, L. J. Zhang et al., “Risk factors of severe hand, foot and mouth disease: a meta-analysis,” Scandinavian Journal of Infectious Diseases, vol. 46, no. 7, pp. 515–522, 2014. View at Publisher · View at Google Scholar · View at Scopus
  22. S. J. Kim, J. H. Kim, J. H. Kang et al., “Risk factors for neurologic complications of hand, foot and mouth disease in the Republic of Korea, 2009,” Journal of Korean Medical Science, vol. 28, no. 1, pp. 120–127, 2013. View at Publisher · View at Google Scholar · View at Scopus
  23. Y. Wang, Z. Feng, Y. Yang et al., “Hand, foot and mouth disease in China: patterns of spread and transmissibility during 2008–2009,” Epidemiology, vol. 22, no. 6, pp. 781–792, 2011. View at Publisher · View at Google Scholar · View at Scopus
  24. A. H. Chou, C. C. Liu, J. Y. Chang et al., “Formalin-inactivated EV71 vaccine candidate induced cross-neutralizing antibody against subgenotypes B1, B4, B5 and C4A in adult volunteers,” PLoS One, vol. 8, no. 11, Article ID e79783, 2013. View at Publisher · View at Google Scholar · View at Scopus
  25. S. L. Liu, H. Pan, P. Liu et al., “Comparative epidemiology and virology of fatal and nonfatal cases of hand, foot and mouth disease in mainland China from 2008 to 2014,” Reviews in Medical Virology, vol. 25, no. 2, pp. 115–128, 2015. View at Publisher · View at Google Scholar · View at Scopus
  26. Q. Y. Mao, Y. Wang, L. Bian, M. Xu, and Z. Liang, “EV71 vaccine, a new tool to control outbreaks of hand, foot and mouth disease (HFMD),” Expert Review of Vaccines, vol. 15, no. 5, pp. 599–606, 2016. View at Publisher · View at Google Scholar · View at Scopus
  27. R. Li, L. Liu, Z. Mo et al., “An inactivated enterovirus 71 vaccine in healthy children,” New England Journal of Medicine, vol. 370, no. 9, pp. 829–837, 2014. View at Publisher · View at Google Scholar · View at Scopus
  28. F. Zhu, W. Xu, J. Xia et al., “Efficacy, safety, and immunogenicity of an enterovirus 71 vaccine in China,” New England Journal of Medicine, vol. 370, no. 9, pp. 818–828, 2014. View at Publisher · View at Google Scholar · View at Scopus
  29. F. C. Zhu, F. Y. Meng, J. X. Li et al., “Efficacy, safety, and immunology of an inactivated alum-adjuvant enterovirus 71 vaccine in children in China: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial,” The Lancet, vol. 381, no. 9882, pp. 2024–2032, 2013. View at Publisher · View at Google Scholar · View at Scopus
  30. F. Y. Yu, R. N. Zhu, Y. Qian et al., “Hand foot and mouth disease associated coxsackievirus A6: recent progress,” Chinese Journal of Viral Diseases, vol. 7, no. 6, pp. 472–477, 2017. View at Google Scholar
  31. X. He, T. Yang, Z. P. Xie et al., “Advances in research on hand, foot and mouth disease caused by coxsackievirus A6,” Chinese Journal of Disease Control & Prevention, vol. 22, no. 3, pp. 321–316, 2018. View at Google Scholar
  32. J. Li, Y. Sun, Y. Du et al., “Characterization of coxsackievirus A6- and enterovirus 71-associated hand foot and mouth disease in Beijing, China, from 2013 to 2015,” Frontiers in Microbiology, vol. 7, p. 391, 2016. View at Publisher · View at Google Scholar · View at Scopus
  33. J. H. Feder, N. Bennett, and J. F. Modlin, “Atypical hand, foot, and mouth disease: a vesiculobullous eruption caused by Coxsackie virus A6,” The Lancet Infectious Diseases, vol. 14, no. 1, pp. 83–86, 2014. View at Publisher · View at Google Scholar · View at Scopus