Respiratory and gastrointestinal infections among Hajj pilgrims during the 2012–2025 seasons: A systematic review

Introduction: Hajj is the largest annual mass gathering in the world, attracting more than 2 million pilgrims from 184 countries. Adverse climatic conditions and close proximity of pilgrims during Hajj rituals create a facilitating environment for the transmission of infectious agents, including multi-drug resistant organisms. Although, several individual reports have been published on specific type of infections, there is a paucity of published work reflecting the overall picture of the prevalence of pathogenic infections during Hajj. Methods: A systematic review was conducted in PubMed, SCOPUS, ScienceDirect, and Google Scholar to examine the prevalence of Hajj-associated pathogenic respiratory and gastrointestinal (GI) infections during the pilgrimage sessions of 2012–2025. Results: A total of 56 studies involving Hajj pilgrims and healthcare workers in close contact with them were included. Most common respiratory viruses detected among pilgrims included influenza and rhinovirus. Bacterial pathogens Streptococcus pneumoniae and Hemophilus influenzae were also detected among the subjects. However, acquisition of the coronaviruses, MERS-CoV or SARS-CoV-2 remained very limited and systematic screening of pilgrims showed limited infections. Amongst the pilgrims with GI infections, Escherichia coli was found to be the commonest bacterial pathogen. Conclusion: This study provides the most updated overview of the prevalence of pathogenic infections during Hajj. While it appears that well-conducted multinational follow-up and post-Hajj studies are necessary for further evaluation of the impact of the Hajj on the acquisition of these pathogens, pilgrims may be at high risk of infections and may carry and transfer them to their home countries. Preventive measures, including hygiene practices and vaccination for high-risk pilgrims should be mandated.