DOI: https://doi.org/10.21203/rs.3.rs-2084643/v1
There are few reports on the timing of onset and characteristics of the symptoms of enterovirus 71 (EV71) infection, which can easily be misjudged by clinicians. This study is aimed to explore the clinical characteristics of children with severe EV71 infection.
This retrospective observational study included children with severe EV71 infection who were admitted to Hebei Children’s Hospital between January 2016 and January 2018.
A total of 101 patients were enrolled, with 57 males (56.4%) and 44 females (43.6%). They were 1–13 years of age. The symptoms were fever in 94 patients (93.1%), rash in 46 (45.5%), a susceptible mood in 70 (69.3%), and lethargy in 56 (55.4%). There were 19 (59.3%) cases with abnormal neurological magnetic resonance imaging [pontine tegmentum (n = 14, 43.8%), medulla oblongata (n = 11, 34.4%), midbrain (n = 9, 28.1%), cerebellum and dentate nucleus (n = 8, 25.0%), basal ganglia (n = 4, 12.5%), cortex (n = 4, 12.5%), spinal cord (n = 3, 9.3%), and meninges]. There was a positive correlation between the ratio of neutrophil count and white blood cell count in CSF in the first 3 days of the course of the disease (r = 0.415, P < 0.001).
The clinical symptoms of EV71 infection are fever and/or skin rash, easy convulsion, and lethargy. Some patients were with abnormal neurological magnetic resonance imaging. The white blood cell count in the cerebrospinal fluid of children with EV71 infection may increase with the ratio of peripheral blood neutrophils in the cerebrospinal fluid of children with EV71 infection.
EV71 is a non-enveloped icosahedron, single-stranded, positive-stranded RNA virus with a total genome length of 7.4 kb that was first isolated from the feces of children in California (USA) in 1969 and has been detected in various countries since then [1–3]. Over the past 20 years, EV71 has also been widely detected in China [4, 5], causing outbreaks and several deaths [6–8]. The virus is obviously neurotropic and can cause an inflammatory response in the body [9–11], leading to various neurological injuries and even death [12, 13].
At present, there are many reports on the common clinical symptoms of infection by the EV71 virus in China [14–16]. Still, there are few reports on the timing of onset and characteristics of these symptoms, which can easily be misjudged by clinicians, especially physicians in rural hospitals, resulting in delayed treatment, improper treatment, or overtreatment.
Therefore, this study aimed to describe the clinical characteristics of children with severe EV71 infection.
This retrospective study included children with severe EV71 infection who were admitted to Hebei Children’s Hospital between January 2016 and January 2018. This study was approved by the Ethics Committee of Hebei Children’s Hospital (152). The requirement for informed consent was waived by the committee because of the retrospective nature of the study.
The inclusion criteria were 1) 28 days to 14 years of age, 2) positive EV71-PCR throat swab, in line with Guidelines for the Diagnosis and Treatment of Hand, Foot, and Mouth Disease (2018 version) [17], and 3) one or more symptoms such as fever, rash, poor mental state, easy to panic, lethargy, limb weakness, ataxia, and cardiopulmonary failure. The exclusion criteria were 1) positive blood culture, 2) increased mycoplasma antibody titers, 3) elevated blood C-reactive protein (CRP) and procalcitonin, or 4) the physicians suspected the presence of other pathogens.
The general information of children with a severe infection of EV71 was obtained from the electronic medical records of the hospital, including sex, age, and fever, dermatosis, irritability, lethargy, limb weakness, white blood cell count, the proportion of neutrophils, white blood cell count of cerebrospinal fluid (CSF), and MRI images of the head and/or spinal cord. MRI examinations of the head and/or spinal cord were performed using a GE Signa Excite 1.5-T imaging system. The images were analyzed and checked by two senior radiologists and pediatric neurologists with more than 10 years of experience.
SPSS 23.0 (IBM, Armonk, NY, USA) was used to process and analyze the data. Continuous data with a normal distribution (according to the Shapiro-Wilk test) were expressed as means ± standard deviation and analyzed using Student’s t-test or the paired t-test. Categorical data were presented as n (%). Two-sided P-values < 0.05 were considered significant.
A total of 101 patients were included. There were 57 males (56.4%) and 44 females (43.6%). They were 1 to 13 years of age (mean: 2.3 ± 1.7 years). Among the 101 patients, 94 (93.1%) suffered from fever, and the onset time was 1.1 ± 0.4 days. Forty-six patients (45.5%) had a rash, and the onset time was 1.1 ± 0.4 days. Seventy (69.3%) children had an irritable mood, and the onset time was 2.7 ± 2.3 days. Fifty-six (55.4%) children were lethargic, and the onset time was 3.8 ± 1.7 days. Two children (2.0%) displayed limb weakness, and the onset time was 5.0 ± 0.0 days. Two patients (1.98%) suffered from ataxia, and the onset time was 3.0 ± 0.0 days (Table 1). Two patients died on the 2nd and 4th days of the course of the disease, respectively.
| Cases | Time (days) | |
|---|---|---|
| Sex | 101 | |
| Male | 57 | |
| Female | 44 | |
| Age, year | 101 | 2.3 ± 1.7 |
| Fever | 94 (93.1%) | 1.1 ± 0.4 |
| Rrash | 46 (45.5%) | 1.1 ± 0.4 |
| Ssusceptibility | 70 (69.3%) | 2.7 ± 2.3 |
| Lethargy | 56 (55.4%) | 3.8 ± 1.7 |
| Limb weakness | 2 (1.98%) | 5.0 ± 0.0 |
| Ataxia | 2 (1.98%) | 3.0 ± 0.0 |
| White blood cell count (×109/L) | 88 | 12.5 ± 4.2 |
| Neutrophils (×109/L) | 88 | 53.2 ± 18.0 |
| White blood cell count of cerebrospinal fluid (×109/L) | 63 | 114.8 ± 126.7 |
Thirty-two children underwent an MRI of the head and/or spinal cord. The MRI examination was performed in the acute phase (within 1 week), and the average time of MRI examination was 3.2 ± 2.8 days from the onset of the disease. Among the 32 children, nineteen showed abnormal neurological imaging, accounting for 59.3%. The abnormal sites were pontine tegmentum (n = 14, 43.8%), medulla oblongata (n = 11, 34.4%), midbrain (n = 9, 28.1%), cerebellum and dentate nucleus (n = 8, 25.0%), basal ganglia (n = 4, 12.5%), cortex (n = 4, 12.5%), spinal cord (n = 3, 9.3%), and meninges (n = 1, 3.1%) (Fig. 1).
The blood routine white blood cell count within 3 days of the disease course was 5.7×109/L to 25.9×109/L. The proportion of neutrophils was 13.9–89.7%. Sixty-three patients underwent CSF examination within 3 days of the disease course. The white blood cell count in CSF was 0 to 587×106/L (Table 1). The proportion of neutrophils within 3 days was divided into quintiles, with 20% per quintile. The proportions of neutrophils in the quintiles were positively correlated with the white blood cell count in CSF within 3 days (r = 0.415, P < 0.001) (Table 2).
| Proportion of neutrophils within 3 days of the disease course | White blood cell count of cerebrospinal fluid within 3 days of the disease course |
|---|---|
| < 20% (n = 8) | 45.1 ± 20.5 |
| 20%-40% (n = 12) | 83.5 ± 94.5 |
| 40%-60% (n = 15) | 115.3 ± 164.3 |
| 60%-80% (n = 25) | 125.7 ± 108.3 |
| > 80% (n = 3) | 331.7 ± 139.2 |
Forty patients were monitored using scalp EEG within the first 4 days of the disease. Among them, 37 (92.5%) children had a normal EEG. Three (7.5%) children showed slow waves of 1.0–2 Hz, and all three suffered from epilepsy-like seizures (Fig. 2).
The results suggest that children with severe EV71 infection are fever and/or skin rash, easy convulsion, and lethargy. Some patients are with abnormal neurological magnetic resonance imaging. The white blood cell count in the cerebrospinal fluid of children with EV71 infection may increase with the increase in the ratio of peripheral blood neutrophils within the first 3 days of illness. The results may provide a deeper understanding of the clinical characteristics of the disease.
This study found that fever and rash tended to appear earlier in the course of EV71 infection, followed by susceptibility and lethargy, which might be related to the infection mechanism. Indeed, EV71 enters the human body through the mouth, initially replicates in the pharynx (tonsils) or intestinal tract, and then multiplies in the regional lymph nodes, which can cause mild viremia [18–20]. The illness of most infected people can be controlled at this stage. In a small number of infected people, the virus continues to invade the reticuloendothelial tissue, deep lymph nodes, liver, spleen, bone marrow, skin, mucous membranes, central nervous system, and heart, and further proliferate and cause corresponding lesions [21]. Generally, the symptoms of systemic viremia, such as fever and rash, appear first after reproduction through the respiratory tract or gastrointestinal tract. If the disease continues to progress, the nervous system can be impaired, leading to susceptibility and lethargy.
In this study, susceptibility usually appeared on the 1st to 4th day, especially on the 2nd or 3rd day. The essence of susceptibility is myoclonus, which is divided into myoclonus from the corticothalamic axis and subcutaneous non-epileptic myoclonus originating from the back of the pons. Considering the fact that no epilepsy waves were found in the scalp EEG of the included children and MRI lesions were more common in dorsal pons, it is possible that susceptibility is from myoclonus caused by the release of 5-HT from the dorsal pons (predominant raphe nucleus) [22]. Lethargy mostly occurred after the fever subsided and the end of susceptibility, mainly on the 3rd or 4th day, and lasted for 1–2 days. Impairment of the cortical or ascending reticular activation system can reduce the level of consciousness [23–25]. Still, most of the children had normal EEG without obvious cognitive dysfunction during the recovery period, suggesting that it is likely that the non-specific projection system damage of the ascending reticular activation system in the upper pons or lower part of the midbrain led to lethargy.
Among the 101 children included, two died. None of the remaining children entered the stage of cardiopulmonary failure or pre-cardiopulmonary failure. Nevertheless, the frequencies of susceptibility and lethargy were 69.3% and 55.4%, respectively, suggesting that susceptibility and lethargy are common clinical manifestations of central nervous system involvement in most children with EV71 infection. In recent years, with the use of immunoglobulin, the number of cases of limb weakness has decreased compared with early studies. Limb weakness mostly occurred after the 4th day and resulted from the anterior horn of the spinal cord being invaded by the virus. The two cases of death due to cardiopulmonary failure occurred in the first 3 days of the course of the disease, mostly without skin rash. Considering that the lesions involved the dorsal nucleus of the vagus nerve and the nucleus of the solitary tract, or the inner acceleration center or vasoconstriction center of the reticular structure [26, 27], it is possible that the lesions are caused by sympathetic excitation.
MRI was performed on 32 patients in this study. The lesions involved pontine tegmentum (43.8%), medulla oblongata (34.3%), midbrain (28.1%), cerebellum and dentate nucleus (25.0%), basal ganglia (12.5%), cortex (12.5%), spinal cord (9.3%), and meninges (3.1%), consistent with that reported by Lee et al. [28]. In this study, the incidence of radiographic infection sites was consistent with the incidence of corresponding clinical manifestations in children: susceptibility (raphe nucleus), lethargy (ascending reticular activation system), ataxia (cerebellum and dental nucleus), limb weakness (anterior horn of the spinal cord), seizures (cortical) and meningeal irritation (meningeal).
Sixty-three patients underwent CSF examination within 3 days of the onset of the disease. The proportion of neutrophils was positively correlated with the white blood cell count in CSF within 3 days of the onset of disease, suggesting that with the increase of the proportion, the white blood cell count in the cerebrospinal fluid has a gradually increasing trend, which has not been reported and has certain significance for guiding the clinical cerebrospinal fluid examination of children with EV71 infection.
There was some limitations. Only one center was involved, leading to a small sample size. In addition, the numbers of patients with EV71 infection in the third and fourth stages were small. The retrospective nature of the study limited the data to those available in the charts. The mechanism of the EV71 virus invading the nervous system and the relationship between different mechanisms and the speed and severity of disease progression are not fully understood, and further research is needed.
This study showed that the common clinical symptoms of EV71 infection were generally fever and/or rash, susceptibility, and lethargy. Some children were with abnormal neurological magnetic resonance imaging. There was a positive correlation between the ratio of neutrophil count and white blood cell count in CSF in the first 3 days of the course of the disease. EV71 infection may involve multiple parts of the nervous system, mainly the pontine tegmentum, consistent with corresponding clinical manifestations.
enterovirus 71
cerebrospinal fluid
Ethics approval and consent to participate
This work has been carried out in accordance with the Declaration of Helsinki (2000) of the World Medical Associatio. This study was approved by the Ethics Committee of Hebei Children’s Hospital (152). The requirement for informed consent was waived by the Ethics Committee of Hebei Children’s Hospital because of the retrospective nature of the study.
Consent for publication
Not applicable
Competing interests
The authors declare that they have no competing interests.
Availability of data and materials
All data generated or analysed during this study are included in this published article.
Authors' contributions
Wenjuan Wu and Baoguang Li carried out the studies, participated in collecting data, and drafted the manuscript. Baoguang Li and Tao Xie performed the statistical analysis and participated in its design. Wenjuan Wu and Tao Xie participated in acquisition, analysis, or interpretation of data and draft the manuscript. All authors read and approved the final manuscript.
Funding
None.
Acknowledgements
None.