General characteristics of the retrieved documents
The search strategy retrieved 509 documents related to religious mass gatherings of Muslims. The retrieved documents were of seven types, mainly research articles (n = 346, 68.0%). Other types of retrieved documents are shown in Table 1. The retrieved documents have 2811 author names, an average of 5.5 authors per document. Of the retrieved documents, 290 (57.0%) were published in open access journals. Of the 509 documents, 503 (98.8%) were published in English. The remaining documents (n = 6, 1.2%) were published in a non-English language. The retrieved documents received 8504 citations, an average of 16.7 citations per document. Of the 509 retrieved documents, 472 (92.7%) had the keyword “Hajj” in the title.
Growth trajectories of publications and citations
Figure 1 shows the growth trajectory of publications which can be organized into three distinct phases: an emergence phase (≤1998), a fermentation phase (1999–2008), and a take-off phase (2009–2020). The growth of citations during the study period showed a gradual increase that ultimately coincided with that of the number of publications.
The retrieved documents were published in 181 peer-reviewed scientific journals. The Travel Medicine and Infectious Disease journal (n = 57, 11.2%) ranked first in the number of publications. Table 2 shows the ten core journals. The Lancet journal ranked fifth in the core list. The majority of the journals in the core list were in the field of infectious diseases or public health or both.
In total, 2811 authors participated in publishing the retrieved documents. Memish, Z.A. (Saudi Arabia) ranked first (n = 107, 21.0%) in the number of publications. Table 3 shows the ten core researchers in the field. The core researchers were from Saudi Arabia, France, and Australia.
Authors from 61 different countries participated in publishing the retrieved documents. Saudi Arabia was the indisputable leader in this field, publishing more than half (n = 278, 54.6%) of the retrieved documents. Table 4 shows the ten core countries in the number of publications. The list of core countries included the US, France, the UK, Australia, Canada, and India with large Muslim communities. At the institutional level, the Ministry of Health of Saudi Arabia ranked first in the number of publications with 146 (28.7%) documents.
Networks of author collaboration
Figure 2 is a network visualization map of authors with a minimum of 10 publications. The map included 27 authors. The red cluster included 11 authors and represented Saudi researchers led by Memish, Z.A. The Saudi cluster existed in the center with collaborative ties with the two remaining clusters. The blue cluster represented French researchers while the green cluster represented Australian researchers.
Networks of international research collaboration
Figure 3 is a network visualization map of countries with a minimum of 10 publications (n = 14). The map shows Saudi Arabia in the center of the map with collaborative ties with most countries on the map. The strongest international research collaboration was between Saudi Arabia and the US, followed by Saudi Arabia and France, Saudi Arabia and Australia, and Saudi Arabia and the UK.
Co-occurrence analysis of author keywords (important topics)
Figure 4 shows a co-occurrence analysis of author keywords with a minimum occurrence of five. The analysis excluded keywords related to “mass gatherings”. Important keywords in the map included vaccination, respiratory tract infections, influenza, coronavirus, prevention, and knowledge.
Most frequent terms in titles/abstracts (major research themes)
Network visualization map of terms in titles and abstracts with a minimum occurrence of five were mapped resulting in four clusters (research themes) (Fig. 5). The clusters were as follows:
The yellow cluster represents surveys and questionnaire-based studies on knowledge, attitude, and practices of pilgrims to Mecca/Makkah
The green cluster represents studies on vaccine-preventable outbreaks of meningitis, pneumonia, and other infections
The red cluster represents studies on etiology and epidemiology of hospital admission among pilgrims in Mecca/Makkah
The blue cluster represents studies on prevention, symptoms, and epidemiology of various viral infectious diseases
Disciplines underlying the foundations of the field
Figure 6 is a co-citation analysis of journals with a minimum citation of 10 (n = 105 journals). The node size represents journals that were most commonly co-cited by journals having similar node colors. The subject area(s) of the journals with the largest node size represents disciplines underlying the field. In the current study, the field of mass gatherings of Muslims was formulated by general medicine (The Lancet, Saudi Medical Journal), infectious diseases/public health (Vaccine, Journal of Travel Medicine, Travel Medicine and Infectious Diseases), and infectious diseases (International Journal of Infectious Diseases, Emerging Infectious Diseases).
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