Objective  To investigate the relationship between severe hand-foot-mouth disease (HFMD) and respiratory tract infection, and to provide suggestions for the prevention of severe HFMD.

  Methods  The study included 428 children with HFMD hospitalized in a county hospital from May to November 2015. Clinic and demographic information of the participants were extracted form their medical records. The participants were then assigned into a common and a severe HFMD group according to the "Guidelines for Diagnosis and Treatment of Hand-Foot-Mouth Disease (2013)". The relationship between severe HFMD and respiratory tract infection was analyzed with chi square test and multivariate logistic regression.

  Results  Of the participants, 200 (46.73%) and 228 (53.27%) were severe and common cases; 328 (76.64%) were complicated with respiratory tract infection; 262 (61.21%) were complicated with tonsillitis and 83 (19.39%) with lower respiratory tract infection, respectively. Statistically significant correlation was observed between severe HFMD and respiratory tract infection (χ² = 15.6361, P < 0.000 1; odds ratio OR = 0.398, 95% confidence interval 95% CI: 0.251 – 0.633). There was a significant correlation between severe HFMD and tonsillitis (χ² = 12.010 1, P = 0.000 5, OR = 0.500, 95% CI: 0.337 – 0.742) but no significant correlation was found between severe HFMD and low respiratory tract infection (χ² = 0.860 2, P = 0.353 7). The associations of respiratory tract infection and tonsillitis with severe HFMD were of significance after adjusting for fever, maximum body temperature, rash, and medication before hospital admission (both P < 0.0001).

  Conclusion  Severe HFMD is associated with respiratory tract infection and the correlation is due to the association between severe HFMD and tonsillitis. The child HFMD cases complicated with tonsillitis are less likely to develop severe HFMD compared to common HFMD cases.