Infection is an established driver of exacerbations and disease progression in bronchiectasis, however, while acknowledged, geographic variation in disease has not been previously reviewed. Chandrasekaran et al. performed a comprehensive review of this understudied area of disease heterogeneity that has emerged in recent times, further evidenced by the contrasting results from the RESPIRE 1 and 2 trials performed across geographically distinct regions [
18‐
21]. Three original articles focused on non-tuberculous mycobacteria (NTM), viruses and paediatric microbiomes are further important additions to this special issue. Lim
and colleagues illustrate that NTM profiles in an Asian setting (Singapore) are unique with
M. abscessus commonest and associated with high rates of pulmonary tuberculosis, itself a major contributor to the bronchiectasis burden in Asia [
22]. Mitchell et al. examined viruses in stable and exacerbating bronchiectasis in a pilot study [
23]. The strength of this work is a weakness of prior studies in this area: an assessment of viral prevalence in the stable clinical state. The authors detect viruses at high frequency from respiratory secretions and exhaled breath, even in the stable state and with the absence of clinical symptoms, questioning their ‘true’ relevance in bronchiectasis. Longitudinal studies are clearly required including those focused on the host ‘virome’ to provide greater clarity to these findings. In contrast to the ‘virome’ , the microbiome in bronchiectasis has been better studied and Masekela et al. further add to this by assessing the lung microbiome in children with human immunodeficiency virus (HIV)-related bronchiectasis, a field where minimal data currently exists [
24]. This study showed a less diverse and largely heterogeneous microbiome dominated by Proteobacteria when compared to a small control group with CF illustrating the contrasting pathologies leading to bronchiectasis in the context of susceptibility to infection.