Thirty-five years (1986–2021) of HIV/AIDS in Nigeria: bibliometric and scoping analysis

Background Acquired immunodeficiency syndrome (AIDS) is an acquired defect of the cellular immunity associated with the infection by the human immunodeficiency virus (HIV). The disease has reached pandemic proportion and has been considered a public health concern. This study is aimed at analyzing the trend of HIV/AIDS research in Nigeria. Method We used the PUBMED database to a conduct bibliometric analysis of HIV/AIDS-related research in Nigeria from 1986 to 2021 employing “HIV”, “AIDS”, “acquired immunodeficiency syndrome”, “Human immunodeficiency virus”, and “Nigeria” as search description. The most common bibliometric indicators were applied for the selected publications. Result The number of scientific research articles retrieved for HIV/AIDS-related research in Nigeria was 2796. Original research was the predominant article type. Articles authored by 4 authors consisted majority of the papers. The University of Ibadan was found to be the most productive institution. Institutions in the United States dominated external production with the University of Maryland at the top. The most utilized journal was PLoS ONE. While Iliyasu Z. was the most productive principal author, Crowel TA. was the overall most productive author with the highest collaborative strength. The keyword analysis using overlay visualization showed a gradual shift from disease characteristics to diagnosis, treatment and prevention. Trend in HIV/AIDS research in Nigeria is increasing yet evolving. Four articles were retracted while two had an expression of concern. Conclusion The growth of scientific literature in HIV/AIDS-related research in Nigeria was found to be high and increasing. However, the hotspot analysis still shows more unexplored grey areas in future. Supplementary Information The online version contains supplementary material available at 10.1186/s12981-022-00489-6.

micrometer and increased susceptibility to opportunistic infection [1].
The first cases of AIDS were reported in May 1981 in the United States of America by Dr. Michael Gottlieb of the Medical School of Los Angeles, United States, and was followed by an official report by the Centre for Disease Control (CDC) on June 5, 1981. The first victims were five homosexual men who were suffering from unusual pneumonia called Pneumocystis Carinii pneumonia and Kaposi's sarcoma. The causative organisms were first isolated and named Human T-Lymphotropic Virus type III (HTLV-III) in the US and Lymphadenopathy Associated Virus (LAV) in France [2][3][4]. Specifically, Luc Montagnier and colleagues in Pasteur Institute France in 1983 first isolated the causative organism [5]. The following year (1984) Robert Gallo of the National Institute of Health isolated the causative organism (HTLV-III) [6,7]. At the same time, Jay Levy and colleagues at UCSF also independently isolated the virus [8,9]. However, Robert Gallo was the first to lay a causative link between the virus and AIDS. In May 1986, the international community on taxonomy of viruses chaired by Harold Varmus harmonized and recommended the renaming of the virus with different names to human immunodeficiency virus, following the evidence that they (HTLV-III and LAV) were genetically indistinguishable [10].
On the African Continent, HIV/AIDS was first reported in Uganda, East Africa in 1982 [11].
The first case of HIV and AIDS in Nigeria was identified in 1985 and reported at an international conference in 1986. The first two cases as reported by the Federal Ministry of Health were; a sexually active 13 year-old girl and a female commercial sex worker from a neighboring West African country [2,4].
Nigeria is the most populous African country and the seventh most populous in the world with an estimated population of approximately 206,139.589 people [12,13]. It is located within the eastern strip of West Africa with an area of 923,768 Km 2 [14]. Nigeria is a multiethnic and culturally diverse federation of 36 autonomous states and the Federal Capital Territory [15]. The first HIV/AIDS sentinel survey was conducted in 1991 with a prevalence of 1.8% which since then increased to 3.8% in 1993, 4.5% in 1996, 5.4% in 1999 [16,17] (Fig. 1). Despite the declining prevalence/low prevalence, HIV/AIDS in Nigeria remains a public health concern. Nigeria ranks 4 th in global HIV burden with approximately 1.8 million (estimated) persons living with HIV as of 2019 [18][19][20]. The current national prevalence of HIV in Nigeria is 1.4% and stratification based on states showed the highest prevalence in Akwa Ibom (5.6%), Benue (4.9%), Rivers (3.8%), Taraba (2.7%) and Anambra (2.7%) and the least prevalence in Jigawa (0.3%) and Katsina (0.3%) [21] (Fig. 2).
Bibliometric studies are relevant tools in the social and scientific evaluation of a given discipline within a specified time frame. They serve as proxy markers for the activities in a given field of research. They evaluate progress/growth and identify gaps in research [22,23]. The performance analysis of a selected study discipline is often done via bibliometrics and social network analysis (SNA). While the bibliometric data computes the  basic outputs, the social network analysis interprets the influence of social links and interactions [24].
This study was aimed at identifying the trend as well as the contribution of Nigeria to HIV/AIDS research. The findings of this study is expected to evaluate progress and identify gaps in HIV research in Nigeria as well as give direction to areas of research and research funding.

Data source
The PUBMED database was used for the bibliometric analysis. PUBMED comprises more than 34 million citations for biomedical literature from MEDLINE, life science journals and online books [25]. Ancillary data were retrieved from Google scholar. Retraction watch database was searched to complement PUBMED on retracted articles and those with an expressions of concern [26].

Data collection
We analyzed the bibliometric data on HIV/AIDS study in the PUBMED published from January 1, 1986 to December 31, 2021. The study period was chosen on the assumption that all research on HIV/AIDS in Nigeria were published from 1986 when the disease was first reported in Nigeria. The search was performed on May 15, 2022. We made use of advanced search in PUBMED using "MESH" terms "HIV" and "AIDS" and applied the following keywords: "HIV" [Title/Abstract] OR "AIDS" [Title/Abstract] OR "Acquired Immunodeficiency Syndrome" [Title/Abstract] OR "Human Immunodeficiency Virus" [Title/Abstract] AND "Nigeria" [Title/Abstract]. We retrieved all data under the above predefined search query without restriction on article type. The retrieved data were used to compute bibliometric indicators. Since PUBMED does not store citation records, we retrieved the citation information about authors and articles via Google scholar. We also re-searched PUBMED using the above search descriptors in addition to "Retraction" and Expression of concern". We also searched the Retraction database setting the location to Nigeria. Extra detail on search query is presented in the Additional file 1: Table S1.

Screening protocol and criteria
Only articles with focus on HIV/AIDS in Nigeria were included. Articles that were not focused on HIV/AIDS but mentioned same on passing were excluded as well as those not in Nigeria. There was no restriction on the type of article. Duplicate articles were also removed. Two review groups among the authors independently performed the article selection. Differences in opinion were settled via consensus of both grouping. The full detail of exclusion diagram is presented in the Additional file 2: Fig. S2.

Visualization of social network analysis
We used the VOSviewer (Center for Science and Technology Studies, Leiden University, The Netherlands) version 1.6.18 to map HIV/AIDS terms and collaboration in the retrieved data from PUBMED.

Impact factor
The impact factor (IF) is utilized as a measure of the journal's influence and was originally developed by the Institute for Science Information (Philadelphia PA, USA) as a bibliometric indicator. It is updated annually in the Journal Citation Report (JCR) of Clarivate Analytics and the value is often a marker of prestige. We used JCR data of 2021.

Author/institution participation index
WE evaluated the overall 1986-2021 scientific publication in the discipline of HIV/AIDS in Nigeria. It is the number of documents on the topic in question (in this case HIV/AIDS in Nigeria) by an author/institution with respect to the total publications in that domain.

Keyword analysis
WE used keyword analysis to ratify the trend of discussion and research in view of the disease characteristics, pathology and treatment.

Co-authorship analysis
CO-authorship refers to the interaction of authors contributing to the particular field of study. The co-authorship of papers between authors shows collaboration [24,27]. The co-authorship network map as generated by VOSviewer show collaborative social network of research fields.

Bibliometric mapping
Bibliometric mapping was divided into two parts: coauthorship mapping and co-occurrence mapping. Co-authorship refers to the interactions of authors in institutions contributing to the field of study, while cooccurrence refers to relationship among keywords.
The following keys of interpretation are utilized in the visualization of co-authorship network analysis: The size of the nodes or bubbles (circles) within the network corresponds to the frequency or number of documents from an author or institution. Secondly, the lines or arcs between nodes correlate/reflect the existence and intensity of the co-authorship link. Finally, the last legend is the color of the node: VOSviewer clustering algorithm assigns the colors to the nodes based on the estimation of a measure of similarity between them. Consequently, it is safe to conclude that nodes of same color are related. Also, the shorter the distance between two (2) nodes, the closer the relationship between them [24].
The first publications (2 in number) were published in 1986. There was a slow pace of publication of HIV/ AIDS related literature from then till the year 2004 when publications shot up more than 20-fold. The tempo of research since then has been sustained and has remained ≥ 150 publications per year after 2011 (Fig. 3).

Analysis of proportion of articles by number of authors
Our result showed a large span of number of authors per document ranging from single author documents to > 10 authors per document. Furthermore, the result showed that more than half (59.66%; n = 1668) of the published articles were by collaboration of < 6 authors ( Table 2). The document with the most authors had 324 author signatures and the most frequent number of signatures was 4.

Analysis of most productive institutions
The top most productive institutions in HIV/AIDS research in Nigeria were represented in Table 3. University of Ibadan, Nigeria was the most productive institution (n = 176), followed by the University of Lagos   1.68%). Out of the top 20 institutions, 10 are federal public universities, 6 are federal tertiary health institutions, 2 federal research institutes, 1 State university resident in Nigeria and a USA-based public land-Grant University (Table 3). On account of external participating countries, institutions in the USA produced 12.84% (n = 359) of the total published literature. This was followed by South Africa, United Kingdom, Canada and Netherlands (Table 3). Individual analysis of the USA-based institutions showed that the University of Maryland produced 1.6% (n = 45) of the literature followed by US Centre for Disease Control (0.7%; n = 20), Harvard School of Public Health (0.50%; n = 14), Emory University (0.50%; n = 14), Vanderbilt Institute for Global Health (0.46%; n = 13) and Johns Hopkins Bloomberg School of Public Health (0.39%; n = 11). Among the South African based institutions, the top productive was from University of Kwazulu-Natal (0.46%; n = 13) and University of Western Cape Town (0.23%; n = 7). The top participating institution from UK was London School of Hygiene and Tropical Medicine (0.14%; n = 4), while that of Canada and Netherlands were University of Ottawa (0.18%; n = 5) and Maastrich University, respectively (Additional file 3: Table S3). However, the overall strongest collaboration (9 link strength) was found between the US Military HIV Research Program and Institute of Human Virology University of Maryland. Table 4 Table 5 Table 6 shows the most productive authors in HIVS/ AIDS-related publication in Nigeria by principal author analysis. Iliyasu Z, Folayan MO, Ogoina D, Uneke CJ, Olowookere SA, Aliyu MH, Ogunbayo A, Olakunle BO, Daniel OJ, Aliyu G and Agaba PA were the top productive first authors. Thirteen of the 15 authors are affiliated to Nigeria while the other 2 are affiliated to USA.  (Table 7).

Overall co-authorship analysis of authors
Notably, Aliyu MH (of Vanderbilt University USA) retained the 6th most productive author position by principal author analysis (n = 19) as well as the 3rd most coauthored author (n = 40) while having the 10th highest total link strength. Similarly, Ezeanolue E made it on both list as the 12th most published principal author as well as the 7th most co-authored author and the 12th highest total link strength (Tables 6 and 7). Figure 6 shows hotspot analysis of author keywords used in HIV/AIDS related studies in Nigeria. Keywords appearing more than 10 times were included in the map. Exactly 120 keywords qualified for this. The network visualization stratified the keywords into 5 clusters. Cluster 1 (red) represented treatment, diagnosis, mortality, epidemiology and co-mobility. Tuberculosis (56) and prevalence (41) were the most occurring keywords in cluster 1. However, mortality had higher link strength (70) with other keywords, despite lower occurrence (21). Cluster 2 (green) focused on treatment, epidemiology and comobility. Diseases (104) and viral diseases were the most   (33), condoms (20) and barrier methods (16) were the most prominent keywords in cluster 3. Cluster 4 (yellow) represented keywords on disease characteristics and demographics. Behavior (55), and demographic factors were the most prominent keywords in cluster 4. However, behavior had the highest link strength (with other keywords) in cluster 4. Cluster 5 (purple) represented keywords associated with risk factors/mode of transmission of HIV. Sex behavior (19) and risk factors (13) were the most occurring keywords in cluster 5. Overall, keywords relating to co-mobility with tuberculosis and HIV prevalence were the most occurring keywords (Fig. 6a).

Keywords/hotspot analysis
On the ground of different average appearing year of keywords, VOSviewer under overlay visualization marked keywords included in the map with different colors (Fig. 6b). Keywords in blue appeared earlier than those in green and yellow. Keywords in cluster 1 and a few in cluster 5 appeared in more recent years, revealing epidemiology, antiretroviral therapy and prevention of mother-to-child transmission (PMTCT) as current topics of discussion in HIV/AIDS research in Nigeria (2018.36-2019.60) (Fig. 6b).
Keywords such as antiretroviral therapy and PMTCT showed no links are therefore research areas still open for new researches.

Analysis of retracted articles and those with expression of concerns
Overall, our analysis found 4 retracted articles and 2 articles with expression of concern in HIV/AIDS related publications in Nigeria. Two of the retracted articles were systematic reviews published in Cochrane Database of Systematic Reviews published by Wiley Publishing Company. The other 2 were a conference paper published in Sexually Transmitted Infections (published by BMJ Publishing) and an original article published in African Journal of AIDS Research (published by Taylor & Francis). The 2 articles with expressions of concern were published in Kidney International (published by Elsevier). Most of the reasons for retractions/expressions of concerns were raised by the authors (Table 8).

Discussion
This study provides a quantitative description of HIV/ AIDS related research in Nigeria from 1986 to 2021 in PUBMED. The most utilized document type by the authors was original article implying that the subject matter was mostly experimental or clinical.
The trend of research output on HIV/AIDS in Nigeria showed a progressive increase and reassuring trend. However, we found that there was a sluggish growth of HIV/AIDS related literature in Nigeria until 2004 when dramatic growth was observed with an inflection point at about 2008. The earlier lag in scientific productivity could be related to the initial response to the epidemic. Balogun and colleagues [2] identified three major phases in the development of HIV/AIDS epidemic in Nigeria. First, there was an era of absolute official and personal denial of the presence of HIV/AIDS in Nigeria (1981)(1982)(1983)(1984)(1985)(1986) [2]. A publication in 1987 [28] reported that government officials insisted that AIDS was non-existent in Nigeria even after 18 other African countries had reported the disease. Secondly, there was an era of skepticism and indifference (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997) which was overwhelmed with misconceptions. People described AIDS literally as "American Idea  to Destroy Sex" and some even bragged that Africans were immune to it. Finally, the last phase was the era of reality (1997 till date).
The core journals that served as sources for HIV/AIDS related publication in Nigeria were PLoS ONE, Pan African Medical Journal, African Journal of Reproductive Health, AIDS Care, Journal of Acquired Immune Deficiency Syndrome, African Journal of Medicine and Medical Science. These journals could possibly be avenues for future breakthroughs in HIV/AIDS research in Nigeria. More so, the patronage of PLoS ONE with a high impact factor may not be unconnected to the editorial policy of the journal. PLoS ONE emphasizes scientific rigor of a research work over novelty unlike other journals within that category [29].
The article "Discriminating attitude and practice by health workers towards patients with HIV/AIDS in Nigeria" published in PLoS Medicine was the most cited article. The article was dedicated to assessing the attitude of health care workers toward HIV infected persons in Nigeria; refusal to attend to HIV/AIDS patients, suitability to attend to HIV/AIDS patients in general ward and the need to disclose HIV status to all health workers. The second most cited article was on phases 3 double-blind randomized clinical trial of a vaginal gel intended for prevention of HIV infection. The article with the most citations per year was an article published in Lancet HIV that dwelt on effect of same sex marriage. All the top 10 most cited articles were published in journals with impact factor > 3. The feat of the article published in Lancet is not surprising considering the high impact factor (16.070) and wider coverage of the journal. However, there have been counter argument on the translation of journal impact factor to individual article citation [30].
University of Ibadan, University of Lagos and University of Nigeria, Enugu and Obafemi Awolowo University were the most outstanding in terms of productivity in HIV/AIDS related research in Nigeria. The above institutions have been consistently documented to occupy the top five (5) positions in researches in biotechnology research [31], Lassa fever research [32] and overall research [33]. They are among the early Federal Universities in Nigeria. The University of Ibadan is the first university in Nigeria founded as University College Ibadan (part of University of London) in 1948 and was later converted to indigenous university in 1962 [34]. It has been ranked 1st in Nigeria and 1172nd in the world (2022-2023 World University Ranking) [35]. University of Lagos is a public federal university founded in 1962, and is ranked 3rd in Nigeria and 1924th globally [36]. University of Nigeria, Enugu was formally opened in 1960 as the first indigenous university, and is ranked 2nd in Nigeria and 1775th globally [37]. The top 6 institutions are all institutions located in southern Nigeria.
Institutions in the United States dominated external publications in HIV/AIDS research in Nigeria and accounted for 12.84% of all publications. Prominent among these institutions were University of Maryland USA and Centre for Disease Control. The United States has been in the forefront of HIV/AIDS research/treatment and funding in Nigeria. This has been via national and corporate funding. For instance, the US President's Emergency Plan for AIDS Relief (PEPFAR) has shown the highest commitment in HIV/AIDS research, diagnosis and antiretroviral therapies [38,39]. The AIDS Prevention Initiative (APIN) funded by Bill and Melinda Gates Foundation has offered substantial funds in the form of grants for HIV research and treatment [40]. The dominance of USA in various fields of study is well documented [22,23]. The United States has been reported to have committed 3.45% of her GDP to research and development (R & D) [41].
Crowel TA, Okonkwo P, Aliyu MH, Ndembi N, DakumP,Kanki P, Ezeanolue E, Nowak RG, Baral SD, Adebajo S, Charurat ME and Ake JA were the all-round most productive authors in HIV/AIDS related research in Nigeria. Collaborative link analysis presented Crowel TA, Okonkwo P, Ndenbi N, Nowak RG, Baral BD, Ake JA, Dakum P, Kanki PJ, and others as the most influential in terms of diversity of links. Prominent to note is Crowel TA who is the most productive author as well as the one with the highest collaborative strength. On the other hand, analysis of authors' contribution based on principal author (first author) analysis showed Iliyasu Z, Folayan MO, Ogoina D, Uneke CJ, Olowookere SA, Aliyu MH, Ogunbayo A, Olakunde BO, Olley BO, Sam-Agudu MA, Lawson L, Ezeanolue EE, Daniel OJ, Aliyu G and Agaba PA to be the most productive authors. The above authors in the two categories are core to HIV research in Nigeria and are likely to have tremendous impact in HIV/AIDS research in future.
Analysis of the co-authorship collaboration network showed that Aliyu MH and Ezeanolue were the only authors in the top list of principal authors who had high link strength of collaboration. Also, most of the top authors with high collaborative strength were affiliated to institutions in the United States and some Nigerian government agencies with external funding. Only Okonkwo P of Bingham University (Private University) and Ezeanolue E (University of Nigeria) were the only top list authors from Universities in Nigeria in terms of collaboration. This observation is further corroborated by the institutional collaboration network analysis. The major collaborating institutions were USA-based institutions and externally funded federal agencies. Most of the federal universities only had inter-university collaboration and were in periphery of the network, hence, their exclusion in the network link map. There is poor funding of research in Nigeria, especially with regards to Nigerian Universities. Nigeria spends only 0.13% of her GDP on research and development (R&D) [41]. This is far below the recommended average of 2.3% by Organization for Economic Co-operation and Development (OECD). The only major source of academic funding in Nigerian public universities is TETFUND (Tertiary Education Trust Fund) which is limited and often rationed funds based on grant applications with limited scope (and don't even cover private universities). The bulk of research in tertiary institutions in Nigeria are self-funded by academic staff, graduate students, staff-in-training and are driven by the demand for publication towards career development [42][43][44][45].
The keyword analysis using overlay visualization showed a gradual shift from disease characteristics to diagnosis, treatment and prevention. The current discussions are on mapping current epidemiology, administration of antiretroviral therapy and the prevention of mother-to-child-transmission of HIV. For instance, there have been varying current discussions on trends, predictors, spatial patterns, knowledge and the reduction of mother-to-child transmission of HIV in Nigeria [46][47][48][49][50]. Often, the first response to an epidemic is to characterize the disease followed by diagnosis and possible means of amelioration/cure. With no absolute curative means to HIV and poor access to ameliorative means, preventive measures have becomes the ultimate means to combat the disease especially in resource limited setting such as Nigeria.
The analysis of articles that had post-publication remarks showed 4 articles withdrawn (retracted) and 2 with an expression of concern. We observed that some of the articles continued to accumulate citations even after they were retracted. For example, the article "Higher risk sexual behavior among HIV patients receiving antiretroviral treatment in Ibadan Nigeria" had 18 citations in total, 7 of which occurred after retraction on May 16, 2014. This observation supports the argument and submission of some researchers [51] that most authors do not read most of the articles they cite. Rather, they copy from an already cited page. Simkin and Roychowdhury [52] have even put a number to it by concluding in their research article "Read before you cite" that only approximately 20% of citers read the original article.
The present study may contain some limitations which are inherent in bibliometric studies. First, the criteria mapped out by the PUBMED database themselves determine the subsequent product of the studied materials. Secondly, local journals that were not indexed in PUB-MED within the study period would have been missed. We might have excluded HIV/AIDS research articles in Nigeria if the authors did not include our specific search descriptors. Lastly, we were limited to use PUBMED a free to use database, we may have missed some articles indexed only elsewhere. However, we believe the output is a true representation of research trend in the study domain.

Conclusion
Irrespective of the inherent limitations, we believe that this study has made available a significant representation of the trends in HIV/AIDS research in Nigeria. We have shown that research on HIV/AIDS in Nigeria had a slow start, possibly due to delay in accepting the reality of the