COVID-19 can affect any age. However, globally, the frequency and case fatality of COVID-19 is comparatively low in the pediatric group. Although several studies reported exclusively on children, a few studies compared the demographic and clinical features across different age ranges[24, 25]. Our study presents a comparative analysis of patient characteristics in neonates, infants, and children in the pediatric age group. We also explored the factors affecting death among pediatric patients with COVID-19.
The median age of our participants was 18 months (1.5 years), and we obtained COVID-19-affected neonates aged as low as one day and children as high as 17 years. Nearly half of the participants were aged less than one year, which is higher than that found by Anwar et al. . The median age of pediatric patients with COVID-19 varies from study to study based on the target population and method of selection. A systematic review on the pediatric group by Patel  found that the reported median age ranges from 1 to 11 years. The author also presents a composite mean age of 7.9 years with an age range between 1 day and 17 years, similar to our study. These findings demonstrate the SARS-CoV-2 virus's ability to infect anyone and children most likely got the virus from their infected parents or family members. This assumption is supported by studies among neonates which showed that half of the patients had infections from their infected mother, and one-third were admitted to the hospital .
Males were more common than females in our study, which corresponds to the findings of other studies . We found this true for all age range. The higher affinity of SARS CoV-2 towards males than females might be explained by the fact that angiotensin-converting enzyme 2 (ACE2), the receptor for the virus, is expressed more in the former sex than in the latter along with other sex-based immunological and hormonal differences .
We found that more than 60 percent of pediatric patients had malnutrition irrespective of age group. This finding is important, as nutrition shows a reciprocal relationship with infection, and good nutritional status is associated with good immune function . Additionally, more than half of them had at least one comorbidity, with the frequency being significantly higher among children and infants than among neonates. However, the overall proportion of comorbidities found in our study was higher than that found in other studies  and lower than that in those who needed neonatal intensive care unit admission. Most of the comorbidities were probably coincident or concomitant findings in COVID-19 rather than precipitating factors. As the virus spreads via airborne respiratory droplets and mostly causes mild or asymptomatic disease in the pediatric population, in most cases, it was a coincidental finding in children presenting with other diseases in the hospital. However, some of the diseases might be consequent of COVID
-19 as well. We noted multisystem inflammatory syndrome in 3 children, which was previously established as a rare but severe complication of COVID-19 among children.
Fever was the most common presentation, followed by breathlessness, abdominal pain, cough, seizure, and vomiting, among others. Two previous studies conducted among children with COVID-19 in Bangladesh[26, 32] also noted fever, cough, breathlessness, abdominal pain, and vomiting among the most common presenting features. In a systematic review of individual participant data, Christopher et el reported similar patterns of presentation. However, the proportion of individual symptoms varied among studies. SARS CoV-2 binds with ACE2, which is ubiquitous in the human body with high expression in the lungs, heart, ileum, kidney, and bladder. Hence, despite its entry through the lung, it might produce symptoms involving multiple systems of the body. However, respiratory and gastrointestinal intestinal intestinal presentation is the most common mode of presentation of the disease. We found that neonates were relatively asymptomatic compared to infants and children. Gastrointestinal complaints such as abdominal pain and vomiting were more common among children, and respiratory complaints such as breathlessness and cough were more common among infants. Christopher et el noted that children less than 7 years old tended to present with gastrointestinal complaints compared to older children. Our findings also conform to their results, as most of the child participants in our study were young with a median age of 64 months (5.33 years).
On laboratory investigations, we noted that children had significantly lower WBC counts than neonates and infants, with infants having significantly lower neutrophils and higher lymphocyte counts than children. However, laboratory data varied across pediatric participants based on the presence of various comorbidities and were mostly within the normal range for the participants. Similarly, Patel noted that the test results presented in various studies of COVID-19 children were mostly within the reference range used for that particular study. Interestingly, this is contrary to expected lymphopenia, and an elevated neutrophil-to-lymphocyte ratio has emerged as a characteristic feature of severe COVID-19 , probably because of the predominantly milder form of the disease in children.
Out of 288 participants for whom the outcome was known, 20 (6.9%) pediatric patients with COVID-19 died. However, the case-fatality rate increased to 8.2% when referred patients were excluded. We found that age was associated with death in pediatric patients with COVID-19, while sex, nutritional status, and the presence of comorbidities did not show any association. The proportion of deaths was significantly higher among neonates than among infants and children. This rate is higher than that found by Ghosh et al (1.4%) and Anwar et al (4.1%). The low number of neonates among their studies might explain the difference. However, Trevisanuto et al found zero case fatalities among 44 newborns with COVID-19. The provision of a well-equipped and adequate number of neonatal intensive care units (NICUs) is an important requirement for the appropriate management of these groups of patients. However, this is often not possible in developing countries because of a lack of adequate treatment facilities. This could explain the high mortality among neonates found in our study. Our analysis also revealed that certain investigation results were significantly different between dead and alive patients. However, this might have been influenced by the higher number of neonates dying instead of infants and children, as the physiology of neonates differs fundamentally from that of older children.
The current study was limited by the small sample size collected from a single center, lack of detection of quantitative RT-PCR, radiological investigations, and dynamic detection of inflammatory markers. However, our study provided important insights into similarities and differences in characteristics, presentation, and outcome of COVID-19 among neonates, infants, and children in the context of Bangladesh.