In the current investigation, we evaluate the rate of SARS-CoV2 and HAdV infections in 360 Iranian hospitalized children suspected to COVID-19 from April 2020 to September 2021 and compare the two infections regarding their laboratory, and clinical characteristics at hospital admission. In our study population, HAdV infection rate was 5.3%, which was consistent with previous reports prior and during COVID-19 pandemic[9–12]. Moreover, positivity rates of HAdV infection did not change significantly during 2020 and 2021 and virus continued to circulate despite the social distancing measures during the COVID-19 pandemic. This may because its non-enveloped structure which leaves them more resistant to lipid disinfectant, and its transmission despite mask-wearing. In good conformity with several studies[11, 12], HAdV infection did not show distinct seasonal trends.
This study was performed between second through fifth (Delta variant-predominant period) SARS-COV-2 infection surge in Iran. The majority of study population was less than 5 years old and not eligible for COVID-19 vaccination according to Iran's health ministry immunization program. Real-time-reverse transcription-PCR test is considered the reference standard for diagnosis of SARS-CoV-2 infection in symptomatic children. In the present study, SARS-CoV-2 RT-PCR positive rate was 12.5% in hospitalized children suspected to COVID-19. The positivity rates of SARS-CoV-2 RT-PCR vary between 8.6–34.1% among suspected children cases in different studies[13–16]. It should be noted that a negative RT-PCR test does not exclude SARS-CoV2 infection specifically in hospitalized children due to poor quality of sampling and late testing or testing in late phases of COVID-19 such as Inflammatory phase.
In the present study, SARS-CoV-2 and HAdV co-infection was detected in 1. 1% of hospitalized children cases. Co-infection between SARS-CoV-2 and other respiratory pathogens have been reported worldwide, including sporadic cases of HAdV and SARS-CoV-2 infections[12, 17–23]. To the best of our knowledge, there is only one case report study that described adenovirus coinfection with SARS-CoV‐2 in a 4‐month‐old infant[24], although in some investigations adenovirus and SARS‐CoV‐2 coinfection has been reported in a low number of adult patients[17, 18, 20, 22, 23, 25].
Regarding clinical characteristics in SARS-CoV-2 positive children our results were consistent with previous research where fever was found to be the most common symptom at hospital admission[14, 15, 26–28]. In good agreement with Li et al. research[28]. our results showed that SARS-CoV-2 positive children often appear to have a milder clinical course than children with respiratory HAdV infection. It is not unusual for HAdV respiratory infection to exhibit sore throat, headache, fatigue, lymphadenopathy and conjunctivitis. These findings are supported by previous studies[6, 29, 30]. Compared with those infected with SARS-CoV-2, we found no statistically significant higher rate of any laboratory findings in those infected with HAdV.
In addition, in the current study HAdV and SARS-CoV-2 co-infected children showed mild respiratory symptoms suggesting that viral co-infection had no or limited additional pathogenic role.
The current investigation has several limitations. First, it was a single-center study with limited sample size and large-scale studies are needed. Second, our study did not include children who consulted outpatient clinics. Also our experiments did not determine HAdV types.
The present study demonstrated that HAdV is an important viral infection in hospitalized children suspected to COVID-19. In addition, current study documented SARS-CoV-2 and HAdV co-infection in hospitalized children cases. Our results revealed that SARS-CoV-2 positive children often appear to have a milder clinical course than children with respiratory HAdV infection and children co-infected with SARSCoV-2 and HAdV had less-severe disease on presentation. Additional multicenter studies into SARSCoV-2 and HAdV co-infected patients is required to understand potential viral influence on disease outcome.