SUDANESE JOURNAL OF PAEDIATRICS

2023; Vol 23, Issue No. 1

ORIGINAL ARTICLE

Noma: a PubMed-based informetric analysis of a neglected tropical orofacial disease in Nigeria

Kehinde Kazeem Kanmodi (1,2,3)

(1) Child Health and Well-being (CHAW) Program, Cephas Health Research Initiative Inc., Ibadan, Nigeria

(2) Medical Research Unit, Adonai Hospital, Karu, Nigeria

(3) Faculty of Dentistry, University of Puthisastra, Phnom Penh, Cambodia.

Correspondence to:

Kehinde Kanmodi

Child Health and Well-being (CHAW) Program, Cephas Health Research Initiative Inc., Ibadan, Nigeria.

Email: kanmodikehinde [at] yahoo.com

Received: 04 October 2021 | Accepted: 31 January 2022

How to cite this article:

Kanmodi KK. Noma: a PubMed-based informetric analysis of a neglected tropical orofacial disease in Nigeria. Sudan J Paediatr. 2023;23(1):42–59. https://doi.org/10.24911/106-1633358254

ABSTRACT

Noma is an orofacial gangrenous infection commonly affecting malnourished children in the tropical region of the World, particularly the sub-Saharan Africa. Nigeria is a sub-Saharan African country which is among the countries seriously affected by noma. In Nigeria, noma has been classified as a priority disease. However, only very little attention has been focused on noma research in Nigeria, unlike many other priority diseases. This study conducted an informetric analysis of research outputs on noma in Nigeria, using the PubMed database – a world-leading and authoritative database of medical literature. This study revealed that only 26 PubMed-indexed publications on noma (PONs), published between January 1990 and September 2021, were available. A trend analysis of these PONs showed that the average output (outputs from 1999 to 2020=23) rate per year (from 1990 to 2020 [31 years]) was 0.74 (23/31). Sokoto (n=11), Oyo (n=4) and Kebbi (n=3) were the top three Nigerian states surveyed on noma in the included PONs. Only 12 publications had international co-authors, of which only few publications had co-authors affiliated with institutions in other African countries: South Africa – 5 publications; and Rwanda – 2 publications. Only two publications were funded. Also, the top five prolific Nigerian authors on noma in Nigeria were affiliated with Noma Children Hospital, Sokoto State, Nigeria. In conclusion, PONs by Nigerian authors is so meagre in quantity. This low output is an issue of medical concern. More research focused on noma in Nigeria is needed through funding and other research capacity-strengthening measures.

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KEYWORDS:

Noma; Cancrum oris; Bibliographic; Informetric; Analysis; Nigeria.

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INTRODUCTION

Noma, otherwise known as cancrum oris, is an orofacial gangrenous infection commonly affecting malnourished children in the tropical region of the world, particularly the sub-Saharan Africa [1]. Noma causes severe destruction of the tissues in the facial region, and it is associated with high disability and mortality [2]. Globally, the prevalence of noma is not accurately known; however, according to the World Health Organisation (WHO), it was estimated that about 770,000 people have been affected by the complications of noma [2,3]. Meanwhile, about 140,000 persons are estimated to develop new cases of noma every year [3]. However, it has been argued that the WHO-reported incidence rate might be greatly underestimated because only 1 out of 10 persons with acute cases of noma do seek patient care [4]; hence, many cases might not be picked up in hospital records.

The actual cause of noma continues to generate severe debate [2]; however, malnutrition, immunosuppression, bacterial infection and poor oral hygiene have been implicated in its aetiology [2,5,6]. Noma is a preventable disease [2], if diagnosed at an early stage it can be treated non-surgically [5]. However, at its advanced stage, surgical intervention and rehabilitation are needed [7,8].

Noma remains an unresolved global health problem [9]. In fact, noma is widely advocated to be regarded as a neglected tropical disease (NTD) [1,4,7,9]. Some of the reasons why noma is being suggested to be recognised as an NTD are: (i) many health workers lack the competence to identify noma and make referrals of it at an early stage [10,11], (ii) noma is yet to be included into the WHO list of NTDs [4,12] and (iii) there is lack of extensive public awareness about the disease [4].

According to the WHO, four criteria must be met before a disease can be regarded as an NTD; they include: (i) the disease must be a cause of stigmatisation, morbidity and mortality of the destitute, (ii) the disease must have a primary occurrence in the tropical and sub-tropical parts of the world, (iii) there should be feasible public health strategies that can be adopted to control and prevent such a disease and (iv) there exists insufficient research evidence to determine the best treatment and control options regarding the disease. The above criteria clearly demonstrate that noma is an NTD.

Nigeria is a country situated in the sub-Saharan African region with millions of households living in abject poverty [13,14], with several non-reported acute cases of noma [15]. Although the national prevalence and incidence rates of noma in Nigeria cannot be accurately established due to limited data, a regional research report showed that the period prevalence of noma in north-central Nigeria is 1.6 per 100,000 population at risk [16].

In Nigeria, noma is yet to be classified as an NTD. However, there have been on-going calls in Nigeria for the consideration of noma as an NTD. In 2019, noma was included in the list of priority diseases in Nigeria. However, only very little funding and other proactive public health measures had been targeted at noma eradication in Nigeria. Measurements of research outputs on the disease can be used as an indicator of the magnitude of public health research efforts geared towards its eradication in Nigeria. Hence, this study aimed to quantify the research outputs (publications) from Nigeria on noma. The outcome of this study will give a revealing picture of the extent of noma research in Nigeria, whether it is scanty or not.

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MATERIALS AND METHODS

Study type

This study was an informetric analysis of PubMed-indexed outputs on noma (PONs) written by Nigerian authors.

Operational terms

In this study, the operational definition of ‘Nigerian author’ is ‘an author affiliated to an institution situated within the geographical borders of Nigeria’ while ‘Nigerian institution’ is ‘an institution situated within the geographical borders of Nigeria’.

Data search and collection

PubMed was used as the database of choice because it is globally recognised as a leading database of medical literature. In the PubMed search, using relevant search combinations (Table 1), a total of 42 publications (hits) were found. The obtained publications were screened for relevance using the criteria listed in Table 1. After the screening, only 26 publications were found eligible to be included in the informetric analysis.

Data analysis

The included publications were analysed manually based on the following parameters: ‘article citation’, ‘access status (open access versus [vs.] paid access)’, ‘publication type’, ‘country of international collaborators’, ‘subject area’, ‘source of funding’, ‘study location by geopolitical zone’ ‘affiliation of Nigerian authors’ and ‘number of publications per Nigerian author’.

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RESULTS

A total of 26 PubMed-indexed publications [13,17–39] published by Nigerian authors and primarily on noma were obtained from our analytical search (Table 2). These papers were published between January 1990 and September 2021 (Figure 1). A trend analysis of these PONs showed that the average output rate per year, from 1990 to 2020 (a total of 31 years), of Nigerian authors (total outputs from 1999 to 2020=23) was 0.74 (23/31, 74.2%).

The majority (20/26, 76.9%) of those included PONs were open access, 15 (57.7%) were original articles, 9 (34.6%) fell under the surgical science subject area, 12 (46.2%) had international co-authors, 2 (7.7%) were funded and 12 (46.2%) studied subjects in north-western Nigeria (Table 3).

Analysis of the distribution of the included PONs by surveyed states showed that Sokoto (n=11, 42.3%), Oyo (n=4, 15.4%) and Kebbi (n=3, 11.5%) were the top three surveyed Nigerian states (Figure 2).

As presented earlier, only 12 (46.1%) out of the 26 included PONs had international co-authors. Of these 12 publications, only few publications had co-authors affiliated with institutions in other African countries: South Africa–5 (19.2%) publications; and Rwanda–2 (7.7%) publications (Table 4).

Only 2 (7.7%) publications were funded (Table 2). However, none of the funding institutions (Médecins Sans Frontières and Nestle Foundation) were owned by the government of Nigeria (Table 5).

Only 21 institutions in Nigeria had authors of PONs. These 21 institutions were situated in only 10 states, out of the 36 states in Nigeria, and the FCT, with roughly one-fourth (5/21) of them in Sokoto State, north-western Nigeria (Table 6).

None of the Nigerian authors of the included PONs had more than seven PONs (Table 5). However, only five authors had between three and six PONs. Also, all these authors were affiliated with Noma Children Hospital, Sokoto State, Nigeria (Table 7).

Table 1. Search objectives, combination of search terms, and screening criteria for included publications.

Search objectives

To search for PubMed-indexed publications written on noma (cancrum oris) in Nigeria

Search combination

((Noma) OR (cancrum oris)) AND (Nigeria[Affiliation])

Inclusion criteria

Publications having their focus on noma or cancrum oris

Publications having at least one author with affiliation to an institution situated within Nigeria

Exclusion criteria

Publications having no focus on noma or cancrum oris

Publications having no author with affiliation to an institution situated within Nigeria

Table 2. List of PubMed-indexed publications on noma (cancrum oris) from Nigerian institutions.

S/N	Article citation	Access status	Article type	Subject area	International authors	Country/ies of foreign author	Funding	Study location by zone
1	Adeniyi SA, Awosan KJ. Pattern of noma (cancrum oris) and its risk factors in Northwestern Nigeria: A hospital-based retrospective study. Ann Afr Med. 2019 Jan–Mar;18(1):17–22. doi: 10.4103/aam.aam_5_18. PMID: 30729928; PMCID: PMC6380110.	Open access	Original article	Clinical epidemiology	No	N/A	Self-funded/Nil	Sokoto State (Northwestern Nigeria)
2	Farley E, Bala HM, Lenglet A, Mehta U, Abubakar N, Samuel J, de Jong A, Bil K, Oluyide B, Fotso A, Stringer B, Cuesta JG, Venables E. 'I treat it but I don't know what this disease is': a qualitative study on noma (cancrum oris) and traditional healing in northwest Nigeria. Int Health. 2020 Jan 1;12(1):28–35. doi: 10.1093/inthealth/ihz066. PMID: 31504549; PMCID: PMC6964223.	Open access	Original article	Behavioural science	Yes	South Africa, Netherlands, United Kingdom, Belgium	Self-funded/Nil	Sokoto State (Northwestern Nigeria)
3	Shaye DA, Winters R, Rabbels J, Adentunji AS, Magee A, Vo D. Noma surgery. Laryngoscope. 2019 Jan;129(1):96–99. doi: 10.1002/lary.27230. Epub 2018 Sep 8. PMID: 30194753.	Open access	Original article	Surgical science	Yes	United States of America, Rwanda, Germany, Ireland	Self-funded/Nil	Sokoto State (Northwestern Nigeria)
4	Farley ES, Amirtharajah M, Winters RD, Taiwo AO, Oyemakinde MJ, Fotso A, Torhee LA, Mehta UC, Bil KA, Lenglet AD. Outcomes at 18 mo of 37 noma (cancrum oris) cases surgically treated at the Noma Children's Hospital, Sokoto, Nigeria. Trans R Soc Trop Med Hyg. 2020 Nov 6;114(11):812–819. doi: 10.1093/trstmh/traa061. PMID: 32785671; PMCID: PMC7645286.	Open access	Original article	Surgical science	Yes	South Africa, Netherlands, United States of America	Self-funded/Nil	Sokoto State (Northwestern Nigeria)
5	Farley E, Oyemakinde MJ, Schuurmans J, Ariti C, Saleh F, Uzoigwe G, Bil K, Oluyide B, Fotso A, Amirtharajah M, Vyncke J, Brechard R, Adetunji AS, Ritmeijer K, van der Kam S, Baratti-Mayer D, Mehta U, Isah S, Ihekweazu C, Lenglet A. The prevalence of noma in northwest Nigeria. BMJ Glob Health. 2020 Apr 14;5(4):e002141. doi: 10.1136/bmjgh-2019-002141. PMID: 32377404; PMCID: PMC7199707.	Open access	Original article	Community epidemiology	Yes	South Africa, United Kingdom, Netherlands, Switzerland	Self-funded/Nil	Kebbi State, Sokoto State (Northwestern Nigeria)
6	Farley E, Lenglet A, Abubakar A, Bil K, Fotso A, Oluyide B, Tirima S, Mehta U, Stringer B. Language and beliefs in relation to noma: a qualitative study, northwest Nigeria. PLoS Negl Trop Dis. 2020 Jan 23;14(1):e0007972. doi: 10.1371/journal.pntd.0007972. PMID: 31971944; PMCID: PMC6999908.	Open access	Original article	Behavioral science	Yes	South Africa, Netherlands, United Kingdom	Self-funded/Nil	Sokoto State (Northwestern Nigeria)
7	Osuji OO. Necrotizing ulcerative gingivitis and cancrum oris (noma) in Ibadan, Nigeria. J Periodontol. 1990 Dec;61(12):769–72. doi: 10.1902/jop.1990.61.12.769. PMID: 2269918.	Open access	Original article	Clinical epidemiology	No	N/A	Not declared	Oyo State (Southwestern Nigeria)
8	Bello SA, Adeoye JA, Oketade I, Akadiri OA. Estimated incidence and Prevalence of noma in north central Nigeria, 2010-2018: A retrospective study. PLoS Negl Trop Dis. 2019 Jul 22;13(7):e0007574. doi: 10.1371/journal.pntd.0007574. PMID: 31329580; PMCID: PMC6675129.	Open access	Original article	Community epidemiology	No	N/A	Self-funded/Nil	Federal Capital Territory, Kogi State, Nasarawa State, Niger State, (Northcentral Nigeria)
9	Miller LE, Shaye DA. Noma and Necrotizing Fasciitis of the Face and Neck. Facial Plast Surg. 2021 Aug;37(4):439–445. doi: 10.1055/s-0041-1722894. Epub 2021 Jan 31. PMID: 33517575.	Paid access	Review article	Surgical science	Yes	United States of America	Information not accessible	N/A
10	Oginni FO, Oginni AO, Ugboko VI, Otuyemi OD. A survey of cases of cancrum oris seen in Ile-Ife, Nigeria. Int J Paediatr Dent. 1999 Jun;9(2):75–80. doi: 10.1046/j.1365-263x.1999.00110.x. PMID: 10530215.	Open access	Original article	Clinical epidemiology	No	N/A	Not declared	Osun State (Southwestern Nigeria)
11	Yunusa M, Obembe A. Prevalence of psychiatric morbidity and its associated factors among patients facially disfigured by cancrum oris in Nigeria a controlled study. Niger J Med. 2012 Jul–Sep;21(3):277–81. PMID: 23304920.	Open access	Original article	Clinical epidemiology	No	N/A	Not declared	Sokoto State (Northwestern Nigeria)
12	Farley E, Lenglet A, Ariti C, Jiya NM, Adetunji AS, van der Kam S, Bil K. Risk factors for diagnosed noma in northwest Nigeria: A case-control study, 2017. PLoS Negl Trop Dis. 2018 Aug 23;12(8):e0006631. doi: 10.1371/journal.pntd.0006631. PMID: 30138374; PMCID: PMC6107110.	Open access	Original article	Clinical epidemiology; Community epidemiology	Yes	Netherlands, South Africa, United Kingdom	Received funding from an organization (Médecins Sans Frontières)	Kebbi State, Sokoto State (Northwestern Nigeria)
13	Denloye OO, Aderinokun GA, Lawoyin JO, Bankole OO. Reviewing trends in the incidence of cancrum oris in Ibadan, Nigeria. West Afr J Med. 2003 Jan–Mar;22(1):26–9. doi: 10.4314/wajm.v22i1.27974. PMID: 12769302.	Open access	Original article	Clinical epidemiology	No	N/A	Not declared	Oyo State (Southwestern Nigeria)
14	Marck KW, de Bruijn HP. Surgical treatment of noma. Oral Dis. 1999 Apr;5(2):167–71. doi: 10.1111/j.1601-0825.1999.tb00084.x. PMID: 10522216.	Open access	Review article	Surgical science	No	N/A	Not declared	N/A
15	Wali IM, Regmi K. People living with facial disfigurement after having had noma disease: A systematic review of the literature. J Health Psychol. 2017 Sep;22(10):1243–1255. doi: 10.1177/1359105315624751. Epub 2016 Feb 1. PMID: 26837690.	Paid access	Review article	Behavioral science	Yes	United Kingdom	Information not accessible	N/A
16	Oji C. Cancrum oris: its incidence and treatment in Enugu, Nigeria. Br J Oral Maxillofac Surg. 2002 Oct;40(5):406–9. PMID: 12379187.	Paid access	Case report	Surgical science, Clinical Epidemiology	No	N/A	Information not accessible	Enugu State (Southeastern Nigeria)
17	Obiechina AE, Arotiba JT, Fasola AO. Cancrum oris (noma): Level of education and occupation of parents of affected children in Nigeria. Odontostomatol Trop. 2000 Jun;23(90):11–4. PMID: 11372157.	Open access	Original article	Clinical Epidemiology	No	N/A	Not declared	Oyo State (Southwestern Nigeria)
18	Isah S, Amirtharajah M, Farley E, Semiyu Adetunji A, Samuel J, Oluyide B, Bil K, Shoaib M, Abubakar N, de Jong A, Pereboom M, Lenglet A, Sherlock M. Model of care, Noma Children's Hospital, northwest Nigeria. Trop Med Int Health. 2021 Sep;26(9):1088–1097. doi: 10.1111/tmi.13630. Epub 2021 Jul 22. PMID: 34080264.	Open access	Original article	Surgical science	Yes	Netherlands	Not declared	Sokoto State (Northwestern Nigeria)
19	Aluko-Olokun B. Face of Noma and Extreme Poverty: Development of an Economic Index Derivable From Health Data. J Craniofac Surg. 2017 Jul;28(5):1342–1343. doi: 10.1097/SCS.0000000000003707. PMID: 28582299.	Paid access	Review article	Health Economics	No	N/A	Information not accessible	N/A
20	Shaye DA, Rabbels J, Adetunji AS, Magee A, Vo D, Winters R. Evaluation of the Noma Disease Burden Within the Noma Belt. JAMA Facial Plast Surg. 2018 Jul 1;20(4):332–333. doi: 10.1001/jamafacial.2018.0133. PMID: 29800992; PMCID: PMC6145668.	Open access	Letter	Community Epidemiology	Yes	United States of America, Rwanda, Germany, Ireland	Not declared	Sokoto State (Northwestern Nigeria)
21	Adeola DS, Obiadazie AC. Protocol for managing acute cancrum oris in children: an experience in five cases. Afr J Paediatr Surg. 2009 Jul–Dec;6(2):77–81. doi: 10.4103/0189-6725.54767. PMID: 19661634.	Open access	Case report	Surgical science	No	N/A	Self-funded/Nil	Kaduna State (Northwestern Nigeria)
22	Idigbe EO, Enwonwu CO, Falkler WA, Ibrahim MM, Onwujekwe D, Afolabi BM, Savage KO, Meeks VI. Living conditions of children at risk for noma: Nigerian experience. Oral Dis. 1999 Apr;5(2):156–62. doi: 10.1111/j.1601-0825.1999.tb00082.x. PMID: 10522214.	Open access	Original article	Health Economics	Yes	United States of America	Received funding from an organization (Nestle Foundation, Laussanne, Switzerland)	Sokoto State, Zamfara State, Kebbi State (Northwestern Nigeria); Lagos State, Kwara State, Ondo State, Ogun State, Osun State, Oyo State (Southwestern Nigeria)
23	Bello SA. Gillies fan flap for the reconstruction of an upper lip defect caused by noma: case presentation. Clin Cosmet Investig Dent. 2012 Jun 1;4:17–20. doi: 10.2147/CCIDEN.S31190. PMID: 23674921; PMCID: PMC3652365.	Open access	Case report	Surgical science	No	N/A	Not declared	Not stated in the publication
24	Farley E, Ariti C, Amirtharajah M, Kamu C, Oluyide B, Shoaib M, Isah S, Adetunji AS, Saleh F, Ihekweazu C, Pereboom M, Sherlock M. Noma, a neglected disease: A viewpoint article. PLoS Negl Trop Dis. 2021 Jun 17;15(6):e0009437. doi: 10.1371/journal.pntd.0009437. PMID: 34138861; PMCID: PMC8211204.	Open access	Viewpoint	Community Epidemiology	Yes	United Kingdom, Netherlands	Self-funded/Nil	N/A
25	Olasoji HO, Tahir A, Adesina OA. Noma in a Nigerian adult. Trop Doct. 2002 Jul;32(3):179–80. doi: 10.1177/004947550203200327. PMID: 12139171.	Paid access	Case report	Surgical science	No	N/A	Information not accessible	Information not accessible
26	Fasola AO, Obiechina AE, Arotiba JT. Unusual presentation of NOMA: a case report. Afr J Med Med Sci. 2003 Dec;32(4):417–8. PMID: 15259930.	Paid access	Case report	Surgical science	No	N/A	Information not accessible	Information not accessible

N/A, Not applicable; S/N, Serial number.

Figure 1. Frequency of PubMed-indexed research outputs on noma by Nigerian authors (January, 1990–September, 2021).

Table 3. Basic characteristics of the included publications.

Characteristics (n=26)	Frequency	Percentage
Access
Open (free) access	20	76.9
Paid access	6	23.1
Publication type
Original article	15	57.7
Review article	4	15.4
Case report	5	19.2
Commentary/Viewpoint	1	3.8
Editorial	0	0.0
Letter/Correspondence	1	3.8
Book chapter	0	0.0
Book	0	0.0
Others	0	0.0
Primary subject areaa
Clinical epidemiology	8	30.8
Community epidemiology	5	19.2
Behavioural science	3	11.5
Surgical science	9	34.6
Health economics	2	7.7
International co-authors
Yes	12	46.2
No	14	53.8
Funding
Self-funded/none	9	34.6
Funded	2	7.7
Not declared	9	34.6
Information inaccessibleb	6	23.1
Study sample location by zonec
North-western Nigeria	12	46.2
North-central Nigeria	1	3.8
North-eastern Nigeria	0	0.0
South-western Nigeria	5	19.2
South-southern Nigeria	0	0.0
South-eastern Nigeria	1	3.8
Information inaccessibleb	2	7.7
Not statedd	1	3.8
Not applicablee	5	19.2

^aSome publications fell under two primary subject areas.

^bRefers to publication lacking a specific information of interest in its abstract (if only the abstract was accessible) or full text (if the full text was accessible).

^cSome publications were surveys of multiple locations.

^dThis refers to publications where the place of study was not specified in its full text.

^eThis applies to non-survey studies.

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DISCUSSION

This study informetrically analysed the PONs by Nigerian authors and the findings obtained are worthy of note. First, the observed total average number of PONs per year, based on the past three decades (1990–2020) among Nigerian authors is less than one. This is a very poor indicator and it confirms that, unlike other infectious diseases like Hepatitis B, dental caries, acquired immunodeficiency syndrome (AIDS), malaria, and typhoid fever which have a very high PubMed-indexed output rate in Nigeria, the research outputs on noma in Nigeria is extremely low.

Based on the study data, it was found that the majority of the included PONs were studied exploring populations in northern Nigeria. This implies that the extent of literature paucity on this subject matter is greater in the southern part of Nigeria than in the northern part. This may suggest that noma is more prevalent in northern Nigeria than in southern Nigeria.

According to WHO, an estimate of 140,000 persons do develop new cases of noma yearly [3]. Based on the WHO data [3], it can be affirmed that noma is not an uncommon orofacial disease, even in Nigeria. Hence, there is a high possibility that many practicing doctors/dentists in Nigeria will encounter at least one person with noma (or a history of noma) during their lifetime of clinical practice. However, only few PONs by Nigerian authors were review articles while none was a book or book chapter. By implication, many doctors/dentists and healthcare professionals in Nigeria will have to rely on non-indigenous books for more information about the noma disease due to this paucity.

Figure 2. Distribution of included publications by states. ‘II’ – Information inaccessible (refers to publication with inaccessible full text, in which study location was not stated in the abstract as well); ‘NS’ – Not stated (this refers to publications where the study location was not stated in its full text); ‘NA’ – Not applicable (this applies to non-survey studies).

Table 4. List and frequency of countries of international co-authors in the included publications.

Countries (Continent)	Frequency of outputsb (n=26)	Percentage
South Africa (Africa)	5	19.2
Netherlands (Europe)	7	26.9
United Kingdom (Europe)	6	23.1
Belgium (Europe)	1	3.8
United States of America (North America)	5	19.2
Rwanda (Africa)	2	7.7
Germany (Europe)	2	7.7
Ireland (Europe)	2	7.7
Switzerland (Europe)	1	3.8

^bSome publications have international co-authors from two or more countries.

Nigeria is a home to hundreds of research-based institutions including universities, polytechnics, colleges, and institutes. However, from January 1990 to September 2021, only 21 institutions in Nigeria have produced authors of the 26 included PONs on PubMed. Also, there is a skewed distribution of these institutions – the majority of these institutions were situated in northern Nigeria. Also, the leading noma researchers in Nigeria, in terms of number of PONs, are all situated in a single institution – Noma Children Hospital. The factors behind the low national rate of institutional outputs of PONs and the skewedness in the distribution of these institutions and authors need to be studied. However, this skewedness may be because Noma Children Hospital is the only referral hospital dedicated to the treatment of noma, unlike other Nigerian institutions. Secondly, the Noma Children Hospital is located in a noma endemic area. In addition, we observed a massive size of research outputs, by Nigerian authors, on Polio, malaria, Hepatitis, AIDS, tuberculosis, and many other infectious diseases, unlike for noma; this further affirms that noma research is a highly neglected public health research area.

Table 5. Authors of publications on noma (cancrum oris) and their characteristics.

S/N	Author name	Affiliation	Total number of publications
1	Adeniyi SA	Noma Children Hospital, Sokoto, Nigeria	1
2	Awosan KJ	Usmanu Danfodiyo University, Sokoto, Nigeria	1
3	Farley E	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	6
4	Bala HM	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	1
5	Abubakar N	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	2
6	Samuel J	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	2
7	Oluyide B	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	5
8	Fotso A	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	4
9	Shaye DA	Doctors Without Borders, Noma Project, Sokoto, Nigeria	2
10	Winters R	Doctors Without Borders, Noma Project, Sokoto, Nigeria	1
11	Rabbels J	Doctors Without Borders, Noma Project, Sokoto, Nigeria	1
12	Adentunji AS	Doctors Without Borders, Noma Project, Sokoto, Nigeria; Children's Noma Hospital, Sokoto State, Nigeria; Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria	6
13	Magee A	Doctors Without Borders, Noma Project, Sokoto, Nigeria	1
14	Vo D	Doctors Without Borders, Noma Project, Sokoto, Nigeria	1
15	Taiwo AO	Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria; Usmanu Danfodiyo University, Sokoto, Nigeria	1
16	Oyemakinde MJ	Médecins Sans Frontières, Noma Children's Hospital, Sokoto, Nigeria	2
17	Torhee LA	Médecins Sans Frontières, Noma Children's Hospital, Sokoto, Nigeria	1
18	Schuurmans J	Noma Children's Hospital, Médecins Sans Frontières, Sokoto, Nigeria	1
19	Saleh F	Nigeria Centre for Disease Control, Abuja, Nigeria	2
20	Uzoigwe G	Nigerian Ministry of Health, Abuja, Nigeria	1
21	Isah S	Noma Children's Hospital, Sokoto, Nigeria	3
22	Ihekweazu C	Nigeria Centre for Disease Control, Abuja, Nigeria	2
23	Abubakar A	Médecins Sans Frontières, Nigeria	1
24	Tirima S	Médecins Sans Frontières, Nigeria	1
25	Osuji OO	University of Ibadan, Nigeria	1
26	Bello SA	Research Division, Cleft and Facial Deformity Foundation (CFDF), International Craniofacial Academy, Gwarinpa, Abuja, Federal Capital Territory, Nigeria; State House Medical Center, Asokoro, Abuja, Nigeria	2
27	Adeoye JA	CFDF, International Craniofacial Academy, Gwarinpa, Abuja, Federal Capital Territory, Nigeria	1
28	Oketade I	CFDF, International Craniofacial Academy, Gwarinpa, Abuja, Federal Capital Territory, Nigeria	1
29	Akadiri OA	CFDF, International Craniofacial Academy, Gwarinpa, Abuja, Federal Capital Territory, Nigeria; University of Port Harcourt Teaching Hospital, Rivers State, Nigeria	1
30	Oginni FO	Obafemi Awolowo University, Ile-Ife, Nigeria	1
31	Oginni AO	Obafemi Awolowo University, Ile-Ife, Nigeria	1
32	Ugboko VI	Obafemi Awolowo University, Ile-Ife, Nigeria	1
33	Otuyemi OD	Obafemi Awolowo University, Ile-Ife, Nigeria	1
34	Yunusa M	Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria	1
35	Obembe A	Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria	1
36	Jiya NM	Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria	1
37	Denloye OO	University of Ibadan, Nigeria.	1
38	Aderinokun GA	University of Ibadan, Nigeria.	1
39	Lawoyin JO	University of Ibadan, Nigeria.	1
40	Bankole OO	University of Ibadan, Nigeria.	1
41	Marck KW	Sokoto Specialist Hospital, Nigeria	1
42	de Bruijn HP	Sokoto Specialist Hospital, Nigeria	1
43	Wali IM	Noma Children Hospital, Nigeria	1
44	Oji C	University of Nigeria Teaching Hospital, Enugu, Nigeria	1
45	Obiechina AE	University College Hospital, Ibadan, Nigeria	2
45	Arotiba JT	University College Hospital, Ibadan, Nigeria	2
46	Fasola AO	University College Hospital, Ibadan, Nigeria	2
47	Shoaib M	Médecins Sans Frontières, Sokoto, Nigeria	2
48	Aluko-Olokun B	International Research Institute for Sciences, Ponyan, Kogi State, Nigeria; University of Ilorin, Ilorin, Nigeria; National Hospital Abuja, Abuja, Nigeria	1
49	Adeola DS	Ahamadu Bello University Teaching Hospital, Zaria, Nigeria	1
50	Obiadazie AC	Ahamadu Bello University Teaching Hospital, Zaria, Nigeria	1
51	Idigbe EO	Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria	1
52	Ibrahim MM	Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria	1
53	Onwujekwe D	Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria	1
54	Afolabi BM	Nigerian Institute of Medical Research, Yaba, Lagos, Nigeria	1
55	Savage KO	University of Lagos, Lagos, Nigeria	1
56	Kamu C	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	1
57	Olasoji HO	University of Maiduguri Teaching Hospital, Borno State, Nigeria	1
58	Tahir A	University of Maiduguri Teaching Hospital, Borno State, Nigeria	1
59	Adesina OA	University of Maiduguri Teaching Hospital, Borno State, Nigeria	1

S/N, Serial number.

Close to half of the included PONs were jointly written by Nigerian authors in collaboration with their international colleagues. This suggests that there exists a well-established international collaborative network of noma researchers in Nigeria. However, they have only little funding.

This study has its limitation. This study was delimited to English papers indexed in the PubMed database only. Notwithstanding this limitation, this study has its strengths. First, this study is believed to be the first study to conduct an informetric analysis of research outputs on noma in Nigeria. Second, the findings obtained in this study highlight the need for more research focused on noma in Nigeria through funding and other research capacity-strengthening measures.

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CONCLUSION

In conclusion, PONs, on the PubMed database, by Nigerian authors are so meagre in quantity. This low output is an issue of medical, social, and public health concern. There is a need for all relevant stakeholders to provide more support for research projects on noma in Nigeria.

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CONFLICT OF INTEREST

The author declare that they have no competing interests.

Table 6. List of Nigerian institutions affiliated with authors of the included publications.

S/N	List of institutions	State/Territoryc
1	Noma Children Hospital	Sokoto
2	Usmanu Danfodiyo University	Sokoto
3	Médecins Sans Frontièresa	Sokoto
4	Usmanu Danfodiyo University Teaching Hospital	Sokoto
5	Nigerian Centre for Disease Control	FCTb
6	Federal Ministry of Health	FCTb
7	University of Ibadan	Oyo
8	International Craniofacial Academy	FCTb
9	State House Medical Centre	FCTb
10	University of Port Harcourt Teaching Hospital	Rivers
11	Obafemi Awolowo University	Osun
12	Sokoto Specialist Hospital	Sokoto
13	University of Nigeria Teaching Hospital	Enugu
14	University College Hospital	Oyo
15	International Research Institute for Sciences	Kogi
16	University of Ilorin	Kwara
17	National Hospital	FCTb
18	Ahmadu Bello University Teaching Hospital	Kaduna
19	Nigerian Institute of Medical Research	Lagos
20	University of Lagos	Lagos
21	University of Maiduguri Teaching Hospital	Borno

^aAlso referred to as ‘Doctors without Borders’.

^bFederal Capital Territory.

^cOnly 10 states, out of the 36 states in Nigeria, and the FCT had institutions with PubMed-indexed outputs on noma.

S/N, Serial number.

Table 7. The five most prolific authors of the included publications.

S/N	Author name	Affiliations	Number of publications
1	Adetunji AS	Doctors Without Borders, Noma Project, Sokoto, Nigeria; Children's Noma Hospital, Sokoto State, Nigeria; Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria	6
2	Farley E	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	6
3	Oluyide B	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	5
4	Fotso A	Médecins Sans Frontières, Sokoto, Nigeria; Noma Children's Hospital, Sokoto, Nigeria	4
5	Isah S	Noma Children's Hospital, Sokoto, Nigeria	3

S/N, Serial number.

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FUNDING

None.

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ETHICAL APPROVAL

Not applicable.

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