Enterovirus genomic load and disease severity among children hospitalised with hand, foot and mouth disease

Abstract

Background: Examining associations between viral genomic loads of enteroviruses and clinical severity is important for promoting and improving development of antiviral drugs related to hand, foot and mouth disease (HFMD).

Methods: Throat swabs were collected from HFMD cases at acute phase of illness using a standardized technique in a prospective study. The viral genomic load was categorized into low, medium, and high groups using parameters of real-time reverse transcription-polymerase chain reaction. The clinical severities were assessed with four indicators, respectively.

Findings: We analysed 1109 HFMD cases, including 538 children with CV-A6, 231 with CV-A16, 156 with EV-A71, 78 with CV-A10, 59 with CV-A4, and 47 with CV-A2. EV-A71 genomic load categories were associated with risks of diagnoses of CNS complications (p = 0.016), requiring systemic corticosteroids or IVIG (p = 0.011), intensive care unit admission (p = 0.002) and length of hospital stay over 5 days (p = 0.048). In the multivariate analyses, point estimates of adjusted odds ratio (OR) tended to increase with viral genomic loads for all four severe outcomes and ORs of highest viral genomic load were all significantly larger than one for EV-A71.

Interpretation: HFMD clinical severities positively associate with viral genomic loads of EV-A71 in throat swabs. Specific antiviral drugs should be developed to reduce enterovirus load and to alleviate the clinical severities for HFMD cases.

Funding: National Science Fund for Distinguished Young Scholars.

Keywords: Clinical severity; Enterovirus; HFMD; Viral genomic load; Viral load.

Fig. 1

Flow diagram of including HFMD inpatient cases in the study.

Fig. 2

The association between virus genomic load and throat swab collection time since illness onset by enterovirus serotype. (a) EV-A71. (b) CV-A6. (c) CV-A16. (d) CV-A10. (e) CV-A4. (f) CV-A2. The line represented the linear regression line and the dashed line represented 95% confidence interval. Lower cycle threshold (Ct) values indicated higher virus genomic loads. The gray dotted line denoted the threshold of Ct value for determining positive in real time RT-PCR.

Fig. 3

Genomic load categories and risks of four clinically more severe outcomes among HFMD cases by enterovirus serotype. (a) EV-A71. (b) CV-A6. The point indicated risks of clinically more severe outcomes and the line indicated the 95% confidence interval. The one and two red stars indicated p values less than 0.05 and 0.01, respectively, using Cochran-Armitage Trend Test. Genomic load categories of EV-A71 were classified based on Ct values as follows: low, ≥34.4; medium, 28.3–34.3; and high, <28.3. Genomic load categories of CV-A6 were classified based on Ct values as follows: low,≥31.2; medium, 26.7–31.1; and high, <26.7.