Human adenovirus infection of 53 children in Jilin Province of China: the clinical and bronchoscopic features

Abstract Background: Human adenoviruses (HAdV) has many kinds of serotypes, of which type 7 can cause severe respiratory disease, especially pneumonia. From Oct 1st to Jan 31st a little outbreak of this type occured in Jilin province of China and led to quite severe pneumonia, therefore we did this retrospective study to summarize the clinical and bronchoscopic features in order to help pediatric physicians get better view of the infection. Methods: Nasopharyngeal swabs or bronchoalveolar lavage fluid (BALF) were collected from pediatric patients who were diagnosed with pneumonia in our department of the First hospital of Jilin University from Oct 1st 2018 to Jan 31st 2019. Then use immunofluorescence method (detect the nasopharyngeal swabs) or the next-generation sequencing technology (detect the BALF) to clarify the pathogen. Results: 53 children were confirmed to be infected with the HAdV, the mean age of infected children was 39.5(39.5±25.09months, 56.6% were less than 36 months. The ratio rate between male and female was 1.3:1. Co-infection was quite common (75%), and happened in older group(p=.018). Bronchoscope was performed on 37 children, 45.9%(n=17) had micro-sputum-bolt in the small distal airway or in the BALF. With the help of the next-generation sequence technology, 11 were confirmed infected with HAdV-7. We followed up the patients for 6 months, 12 by CT and 41 by telephone call. In the CT follow-up group, 8 had “Mosaic sign” on lung CT, and 4 shows mild uneven ventilation. In telephone follow-up group 31 recovered well and had no symptoms, 10 had cough and tachypnea after moderate level of daily activities. Conclusion: A) Compared with previous data in our hospital, in the winter this year, a little outbreak happened in Jilin province of China. B) We infer that HadV-7 may be the prevalent strain. C) Before we get accurate etiology diagnosis, combining with the clinical symptoms, accessory results, the micro-sputum-bolt seen in the BALF when doing the electronic bronchoscope can


Background
Human adenovirus (HAdV) are non-enveloped viruses containing double-stranded linear DNA [1], which were first isolated in 1953 as respiratory pathogens [2,3]. They belong to the family Adenoviridae, genus Mastadenovirus and are categorized into seven species (A-G) according to their biophysical, biochemical, and genetic characteristics [4]. To date, 90 genotypes have been cognized [5]. Among these species, species B (HAdV-B3 and HAdV-B7) are usually associated with 3 respiratory diseases [6]. Moreover, respiratory infections due to HAdV cause significant morbidity and mortality, with case fatality rates as high as 12% [7].
Many outbreaks of acute respiratory infection caused by HAdV have been reported during the last decade in many countries including China [8][9][10][11][12][13][14][15][16][17]. Such outbreaks were also reported in the community and in military and police camps between 2011 and 2013, in Taiwan, Singapore, China and Malaysia [18][19][20][21][22]. From Oct 1st 2018 to Jan 31st 2019 a little outbreak of HAdV happened in Jilin province of China. As the severity and prevalence of such kind of infection, we did the retrospective study.

Study Design
This is a retrospective study, and focus on the inpartment patients who got to our department from  (4)Chlamydia pneumoniae(CP) antibody >1 S/CO;(5) Clearly visible fungal infection of the mouth or vulva;(6) Others: no clear pathogenic evidence was found, but the procalcitonin (PCT) over 1.0ng/ml would also consider the bacterial infection).Among all kinds of co-infection pathogens, MP was the most common in 18 cases, followed by CP and RSV in 5 cases, others are listed in Table 5.

DCell-mediated immunity
We detected the number of immune cells (including the absolute cell counts of CD3+T/CD4+T/CD8+T/CD19+B) in 28 children by flow cytometry. The results showed that the absolute counts of CD3+T cells and CD19+B cells were less than the lower limit of the reference range in 50% of children, and the absolute counts of CD4+T cells were less than the lower limit of the reference range in 64.3% of children (Table 6).

F) Treatment
In terms of drug therapy, the use of IVIG in severe group can reduce the fever days which had no statistically significant difference with the non-IVIG in mild group (p=0.907).

G) Imaging performance and follow-up
After admission, all the 53 cases received pulmonary CT examination, which had the following characteristics: A) Double lobes pneumonia were common, with a total of 40 cases (75.5%) : B) The lower lobe of the left lung was the most easily affected, with a total of 34 cases (64.2%); C) There were 31 cases (58.5%) of eccentric mass and ground glass changes. In addition, there were 8 cases with pleural effusion (all with a small amount of unilateral pleural effusion), among which 6 cases were left pleural effusion. We followed up the patients for 6 months, 12 by CT and 41 by telephone call. In the CT follow-up group, 8 had "Mosaic sign" on lung CT (Picture E and F), and 4 shows mild uneven ventilation. In telephone follow-up group 31 recovered well and had no symptoms, 10 had cough and tachypnea after moderate level of daily activities.

Discussion
According to our study, 86.7% of children younger than 6 years old are infected, which is similar to previous studies [13, 24-27], and mainly concentrated between 6 months and 36 months, which may be because children in this age group will contact more people and led to a higher risk of infection.
Children less than 6 months, however, infection in our study did not find, according to previous studies, this may be because the age children with a mother who give the antibodies against  [32].We have the following hypotheses for the small outbreak of adenovirus in this winter: A) The virus may prefer a warm climate. Compared with previous years, the average temperature in northeast China this winter was higher and the precipitation was less, which may be one of the reasons for the epidemic; B) There have been few reports of adenovirus infection in northeast China in recent years, and the reduced immunity of the population to adenovirus may be the second reason for this outbreak.
In this study, 11 cases of infected children were confirmed to be infected with HAdV-7 by NGS test.
Therefore, we speculated that the HAdV-7 was the epidemic strain that caused the outbreak of infection this winter.
Our study found that the incidence of co-infection was high, but there was no statistical difference in clinical data between the co-infection group and the single infection group, which was similar to previous reports [32,33]. As for the high incidence of co-infection we consider the following aspects: A) According to our study, the cell-mediated immune ability had suppressed, because of that it's easy to get other pathogen infection; B) Nowadays, the pathogen detection methods we use are more and more advanced (for example, NGS mentioned earlier in this paper), making the detection rate of various pathogens significantly higher than before, thus increasing the co-infection rate; C) PCT and 8 C-reactive protein are higher in the study, which often indicate the bacterial infection and led to the widespread use of antibiotics, also had similar situation in other studies [33][34][35], for the immune function suppressed by HAdV children the use of antibiotics will further increase the possibility of other pathogen infection. To sum up, when encountering children who are highly suspected to be infected with HAdV, we should be more cautious about the use of antibiotics, especially when and how to use.
Electronic bronchoscopy has been widely applied in children with lung disease [36,37].

Declarations
Ethics statement The study protocol was approved by the Ethical Review Committee of the First Hospital of Jilin University. All the samples and information we collected were authorized by the children's parents.

Consent for publication
Written consent to publish this case report and any accompanying images has been obtained from the patient's parents.

Availability of data and materials
The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Competing interests
Not applicable