Even as the coronavirus disease 2019 (COVID-19) pandemic tore through the world, with devastating impacts on human health, human life, and the human economy, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seemed to spare children during the initial phase. Not only so, but other virus infections associated with acute respiratory illnesses common in children also dropped steeply.
A new paper compares the infection and hospitalization rates of pediatric patients with acute respiratory illnesses.
The pandemic era was ushered in with new terms like social distancing. At the same time, regular hand hygiene, face mask usage, and shelter-in-place orders became the new normal as part of public health interventions aimed at arresting or at least slowing the pandemic's peak. During this time, it was noted that primary care practices and emergency rooms had much lower rates of patient visits.
This may be attributable to the avoidance of healthcare centers for fear of COVID-19 or because of the steep reduction in respiratory infections due to the containment measures that would be effective against almost any infectious pathogen.
With the autumn wave of the pandemic, acute respiratory infections (ARI) in children went up again but remained at about half the level observed in pre-pandemic years. Influenza infection went down by almost 100% across all age groups that autumn/winter flu season. In Germany, which has a sentinel surveillance system based on physicians, there were only three cases of respiratory syncytial virus (RSV) infection over 30 weeks, from the fortieth week of 2020 onwards.
These trends were seen in several countries. The current study, published in the journal Pediatric Infectious Diseases, examined the incidence of COVID-19 in children with ARI relative to other respiratory viruses during the second and third waves.
What did the study show?
The study was carried out in the German city of Wuerzburg, Germany. All patients who had developed symptoms within 14 days before they presented were eligible. There were 168 children and adolescents with ARI. About a quarter of them had chronic lung disease, including bronchopulmonary dysplasia or asthma, while less than 10% had heart diseases.
Most commonly, the children presented with a runny nose, otitis media, sinusitis, conjunctivitis or laryngitis, all upper respiratory tract infections that made up almost 80% of the total acute conditions, vs. bronchitis, pneumonia, and laryngotracheitis, among the other conditions. In about a fifth of cases, both upper and lower respiratory tract infections were present, with or without fever. Most presented three days after the onset of symptoms, while the median duration of illness was one week.
Two of every three patients had one or more respiratory viruses, almost half being contributed by rhinoviruses. About one in seven was caused by adenoviruses and the same number by coronavirus NL63. SARS-CoV-2, other seasonal endemic coronaviruses, influenza, and parainfluenza viruses were responsible for 1% or less of infections.
In about a fifth of cases, two or more viruses were found in the same child simultaneously, including rhinovirus with adenovirus, coronavirus NL63, bocavirus and parainfluenza virus co-infections, as well as adenovirus-NL63 coinfections. Not a single sample was positive for RSV, enterovirus, or human metapneumovirus.
None of these infections were found to be more common in any age group. Still, virus detection was lowest during the time of strict lockdown (end of December 2020 to end of February 2021), increasing with the relaxation of restrictions.
What are the implications?
This study showed that most ARI during the study period, from November 2020 to April 2021, was due to rhinovirus, seasonal endemic coronaviruses and adenoviruses, which were found in almost two-thirds of the children. Rhinoviruses are notoriously easily spread among children because of poor handwashing techniques and smear or contact infections.
There are over 160 serotypes of this virus, circulating throughout the year, allowing the same children to be infected repeatedly without developing durable type-specific immunity. As for the other two types, they are easily spread by children smearing their infectious nasal secretions on frequently touched surfaces or by contact infection. Moreover, adenoviruses may be found on surfaces despite the use of several disinfectants.
A single SARS-CoV-2-positive sample was found, despite the timing of the study during the peak of the second and third waves. RSV was notably absent, and a single influenza sample was observed, again despite the study being performed during the winter flu season. The strikingly low incidence of these viruses could be due to interruption of virus transmission. Still, the role played by susceptibility differences, in the case of the novel coronavirus, needs to be elucidated further.
The increase in infections with RSV, flu viruses, and SARS-CoV-2 with relaxation in restrictions indicates their potential preventability by strict containment measures. This is not the case with rhinoviruses, and to a smaller extent, by endemic seasonal human coronaviruses. More research may uncover the interaction between different viruses, their transmissibility, and fitness in different environments.
As SARS-CoV-2 continues to evolve, generating new, more infectious and/or immune-evading variants, other, older viruses will continue to cause significant numbers of cases or may appear during the off-season with the relaxation of strict hygiene and anti-transmission measures. This means that healthcare systems should gear up for a potential surge in ARI among children due to these pathogens, which can otherwise take a heavy toll on pediatric health.