Adenovirus infection in children hospitalized with pneumonia in Guangzhou, China

Abstract Background HAdV infection can cause a variety of diseases. Although infections with HAdVs often are mild, life‐threatening respiratory disease can occur. Pneumonia is one of the more serious types of HAdV‐induced respiratory disease in children. In this study, we determined the prevalence and genotype of HAdVs among children hospitalized with pneumonia in Guangzhou, China. Methods Nasopharyngeal swabs (NPSs) were collected from children hospitalized with pneumonia in Guangzhou, China, from January 2013 to June 2019. HAdVs were detected by real‐time polymerase chain reaction assay, and hexon, fiber, and penton gene were amplified and used for phylogenetic analysis. Epidemiological data were analyzed using SPSS16.0 software. Results and Conclusions A total of 1778 children hospitalized with pneumonia were enrolled. The overall HAdV detection rate was 3.26%. And the yearly detection rate varied from around 2.5% in 2013‐2017 to around 6% in 2018‐2019. Children >5 years had the highest HAdV infection rate. 92.86% of HAdV sequences obtained in this study were belonged to species B, and no recombination was observed. HAdV‐B7 and HAdV‐B3 were the common types detected in the study period, with the predominant HAdV genotype shifted from HAdV‐B3 in 2015‐2016 to HAdV‐B7 in 2017‐2018. The discrepancies in HAdV detection rates in different study period and changes of HAdV predominant types over time highlighted the importance of continued surveillance.


| Patients and specimens
Nasopharyngeal swabs (NPSs) used in this study were collected from children (≤15 years) hospitalized with pneumonia in a tertiary maternal and child health care hospital in Guangzhou, China, from January 2013 to June 2019. Patients, who were suspected of having acute respiratory tract infections and were diagnosed with pneumonia by chest radiography, were enrolled in this study. NPSs were collected within 24 h after admission. Specimens were stored in a viral transport medium at −70°C until analysis.

| HAdV and common respiratory virus detection
Total nucleic acid was extracted by the automated nucleic acid human coronavirus/COV) were performed with a one-step reverse transcription polymerase chain reaction (qRT-PCR) as described in previous study. 9

| Phylogenetic analysis
The HAdV sequences generated in this study were aligned with HAdV strain sequences available in GenBank. Multiple sequence alignment was performed using ClustalW, and alignments were minimally edited by hand using Aliview. For genotyping, maximum-likelihood (ML) trees were estimated for hexon, penton, and  populations were compared by chi-square test or Fisher's exact test, as appropriate. Mann-Whitney U test was used when comparing continuous (numerical) variables without normal distribution between the two groups. All tests were calculated in a two-tailed manner, and the statistical significance was set at P < .05 level.

| Patient characteristics and HAdV detection
A total of 1778 children hospitalized with pneumonia were enrolled during the study period (Table 1).These included 1154 males and 624 females (1.85:1). The median age was 11 months (interquartile range, 0.28 ~ 2.6 years), with more than half of the overall patients (60.5%) were children under 1 year of age. HAdV was detected in 58 samples, including 35 males and 23 females (1.52:1). No significant gender difference was observed (P = .459). The overall positive rate was 3.26%. The age of patients infected with HAdV varied from 3 months to 9 years with median age of 1 year and 9 months. Distribution of HAdV prevalence among age groups was significantly different (P = .000). The lowest detection rate was observed in age group of 1-6 months (0.8%, 5/640), while the age group of more than 5 years old had the highest prevalence (6.5%, 11/170). We observed significant different positive rates of HAdV infection over the study years (P = .008, Figure 1). In year 2013-2017, HAdV detection rate was approximately even, ranging from 1.4% to 2.9%. Then, an apparent increase of HAdV circulation in year 2018-2019 was observed, with the positive rate up to 5.6% and 7.7%, respectively. HAdV infections circulated year-round, with a tendency to be more common in the period from November of first year to January of the next, and a small peak between May and July.

| Co-infections with other respiratory viruses
Of the 58 HAdV-positive cases, 18 (31.03%) were co-infected with other respiratory viruses (Table 2). Among which, 14 (77.78%) were with one other virus, 3 (18.75%) with two other viruses, and 1 (6.25%) with four other viruses. As shown in Table 2, HRV (37.50%) and PIV (31.25%) were the two most frequently identified viruses in co-infected cases. No specific dominant genotype for HAdV was observed in co-infections.

| Phylogenetic analysis and genotype distribution patterns
To further analyze the HAdV genotype, the hexon, fiber, and penton gene from HAdV positive specimens were amplified. In total, 56 out of 58 samples had at least one gene amplified. The hexon, fiber, and penton gene were successfully genotyped from 47, 45, and 39 samples, respectively. Consistent genotype distributions of three genes were observed for all Guangdong HAdV sequences, and no recombination was identified ( Figure 2). The majority of HAdV strains were belonged to species B (52, 92.86%), except 4 HAdV stains which were distributed into species C (2) and species E (2), respectively.
For HAdV-B3 strains, sequence analysis also showed high nucleotide sequence homologies (99.7%-100%). All the HAdV-B strains identified in this study were nearly identical to strains recently circulating

| D ISCUSS I ON
The present study reported the recent epidemiological profile of We did not observe any gender difference in HAdV infection, which is consistent with previous studies conducted in other provinces of China. 15,16 However, the predominance of male children was also commonly reported in literature. 8 In our study, the highest HAdV-positive rate was observed among children >5 years of age.
This differs from previous reports that most HAdV infections occurred in early childhood due to the naive immune system. 17 The age differences might be attributed to several factors. In our study,

TA B L E 2 Co-detection of HAdV and other respiratory viruses
HAdV-B7 was the most frequent isolated strains, and children with HAdV-B7 infections tend to be older than those with HAdV-B3. 18 HAdV showed different seasonal patterns in different climatic zones. Previous studies demonstrated that the HAdV detection rates tended to coincide with higher temperature, longer sunshine duration, and lower wind speed. 11 In our study, two peaks of HAdV were detected, maximal in May to July and November to January, consistent with those obtained in other subtropical areas. 8

Reports about HAdV co-infection with other respiratory viruses
were frequent. [19][20][21] In our study, co-infection was identified in 18 out of 58 HAdV-positive cases. Consistent with previous reports, 13 the dominant co-infection with HAdV was HRV and PIV. Because studies has demonstrated that the HAdV predominant types changed over time. 23,24 The HAdV epidemiology data collected in Taiwan showed that the HAdV-B3 has circulated annually and was the dominant circulating genotype causing respiratory infections in children since 1999. 23 An earlier study from our center also Our study analyzed the HAdV infections among children hospitalized with pneumonia in Guangzhou from 2013 to 2019. To our knowledge, this is the first report that describes the prevalence, age distribution, seasonality, and molecular epidemiology of HAdV infections among children hospitalized with pneumonia in Guangzhou.
We found 3.26% of children hospitalized with pneumonia were caused by HAdV infection. And the yearly detection rate varied.
Children >5 years had the highest HAdV infection rate. The majorities of HAdV sequences obtained in this study were belonged to species B. HAdV-B7 and HAdV-B3 were the common types detected, with the predominant genotype changed from HAdV-B3 to HAdV-B7. Our results will form the basis to determine the burden of HAdV infection. The discrepancies in HAdV detection rates in different study period and the changes of HAdV predominant types over time highlighted the importance of continued surveillance.

ACK N OWLED G EM ENTS
We gratefully acknowledge the efforts of the hospital in the inves-