Outbreak of severe acute respiratory infections caused by recombinant human adenovirus type B 7/3 in hospitalized infants from a nursery in Dakar, April 2024

Abstract

Objectives: Acute respiratory infections are among the leading cause of mortality in children under 5 years of age worldwide, with most of these deaths due to bronchiolitis and pneumonia. We investigated and analyzed a pediatric outbreak of acute respiratory infections that resulted in the hospitalization of four infants in a nursery in Dakar in late April 2024.

Methods: Nasopharyngeal specimens were collected from infants and tested for a panel of respiratory pathogens by multiplex real-time reverse transcription-polymerase chain reaction. Subsequently, the positive samples underwent next-generation sequencing for molecular analysis.

Results: Human adenovirus (HAdV) was the principal etiologic agent detected in hospitalized infants with pneumonia and nearly half (46.7%; seven of 15) of the suspected cases identified during the investigation at the nursery. All the HAdV isolates were classified as being of subgroup B1. Molecular characterization revealed that infants attending the nursery were infected with a recombinant HAdV strain containing an adenovirus serotype 7 penton and serotype 3 hexon and fiber proteins.

Conclusions: Our findings reinforce previous evidence that recombination leads to the emergence of new adenovirus strains with epidemic and lethal potential. These results emphasize the need to strengthen surveillance in inpatient settings across the country.

Keywords: Dakar; Human adenovirus; Infants; Nursery; Outbreak; Recombination.

Figure 1

Maximum likelihood phylogenetic trees based on nucleotide sequences of the penton (a) and hexon (b) genes of HAdV-B. The trees were constructed using IQ-TREE (v.2.0.6) and visualized with Figtree software version 1.4.4. Statistical significance was tested by 1000 bootstrap replicates, and the software determined the best-fit model. Sequences highlighted in red represent recombinant HAdV-B7/3 strains associated with the outbreak at the nursery in Dakar. The trees were rooted using an HAdV type F strain. Values on the trees represent bootstrap support values, indicating the robustness of the clades in the phylogenetic trees.

Figure 2

An analysis of potential recombination events within the complete genome sequences of the three Senegalese human adenovirus was conducted using the recombination detection program package Beta 4.97 in default mode. Potential major and minor parents of these recombinant strains are shown as dark cyan and purple lines, respectively, along with the sequence break points.