Thirty years of research in tropical medicine: historical trends for the world and for the Revista de Biología Tropical (1990-2020)

Introduction: The importance of tropical medicine cannot be overstated, since by the end of the 2030s, most humans will live in the tropics and will need protection from tropical diseases. Nevertheless, until now, there are no bibliometric studies about tropical medicine as a whole; all previous studies are limited to diseases, countries or particular journals, and are often limited to brief periods of time. Here we present an analysis of historical trends for the world and for the Revista de Biología Tropical in celebration of the journal’s 70 th anniversary. Objective: To assess geographic and historical trends in the study of tropical medicine included in a general database, the Web of Science and from a detailed analysis of one journal of particular importance for the field in the neotropical region. Methods: We limited our data to journals covered by the Web of Science category “tropical medicine” in the Science Citation Index Expanded (data updated 19 January 2022) and the Journal Citation Report on 30 June 2021. Results: We retrieved 69 480 articles, of which 44 % resulted from international collaboration with 194 participating countries; articles may reach 17–21 citations each, and the countries with outstanding results in the data-base include USA, Brazil, UK, Kenya and Switzerland. Research focus changes as diseases such as HIV, Dengue and tuberculosis become more or less important over time, but overall there was much research on Plasmodium , leishmaniasis and schistosomiasis. The journal Revista de Biología Tropical has significantly increased the number of topics covered, but still publishes studies about tropical biomedical subjects. Conclusions: While countries with large research budgets have a large presence in this database, lower income tropical countries like Brazil and Kenya have done a remarkable contribution in the field of tropical medicine. The Revista de Biología Tropical has been publishing quality research about tropical medicine for the last seven decades.


INTRODUCTION
This article was written in celebration of 70 years of the Revista de Biología Tropical, an international journal published by the University of Costa Rica, but covers both the history of tropical medicine in the journal, and the world-wide trends of the field in the last thirty years.The journal was established as part of a movement to modernize the country that started in the mid-20th century (Gutiérrez, 1986); the idea of the journal was first proposed in 1949 by Alfonso Trejos Willis (Zeledón, 2015) and in its early years it mostly published tropical medicine contributions originating in the Hospital San Juan de Dios and the University of Costa Rica (Girolami, 1988;Gutiérrez, 2002).Over the years, the journal grew significantly in other fields of biology, like marine biology, and the health-related content became a smaller percent of content in each issue but remained stable in total numbers at around 80 publications per decade (Gutiérrez, 2002).
Tropical medicine is relatively a recent concept, a field that has been studied under that name for only about a century (Keiser & Utzinger, 2005); the concept was born from the need that European empires had to control disease in the invaded African lands (Packard, 2012).Its importance is clear: at the end of the 2030 decade, most humans will live in the tropics and will need protection from tropical diseases (Wilkinson, 2014).
An early attempt to study the bibliometrics of research in tropical medicine reported a high concentration of articles in relatively few journals, and the predominance of the English language in the sample (Brennen & Davey, 1978); however, the study was based on a handful of American and European journals and considered only a brief period (1972)(1973)(1974)(1975), making any generalizations unwarranted.
Decades passed before another study, which covered the period 1996-2003 and only one European journal, provided new information; unsurprisingly, this limited study found that Europe produced most of the papers published in the journal, but, surprisingly, also found that Africa was not far behind in number of articles, and that African authors were highly cited (Glover & Bowen, 2004).It also found that many papers were about Malaria, HIV/AIDS, tropicales.Sin embargo, hasta el momento no hay estudios bibliométricos sobre la medicina tropical en su conjunto; todos los estudios previos se limitan a enfermedades, países o revistas particulares y, a menudo se limitan a períodos breves de tiempo.Acá presentamos un análisis detallado de tendencias históricas en el mundo y en la Revista de Biología Tropical, para celebrar los 70 años de la revista.Objetivo: Evaluar las tendencias geográficas e históricas de la medicina tropical usando los artículos científicos incluidos en la base de datos Web of Science.Además de un análisis detallado de una revista de particular importancia en la región neotropical.Métodos: Limitamos nuestros datos a las revistas cubiertas por la categoría "medicina tropical" en el Science Citation Index Expanded (datos actualizados el 19 de enero de 2022) y el Journal Citation Report del 30 de junio de 2021.Resultados: Identificamos 69 480 artículos, de los cuales el 44 % resultó de la colaboración internacional con 194 países participantes; los artículos pueden llegar a 17-21 citas cada uno, y los países con resultados destacados en la base de datos incluyen EE.UU., Brasil, Reino Unido, Kenia y Suiza.El enfoque de la investigación cambia a medida que enfermedades como el VIH, el dengue y la tuberculosis se vuelven más o menos importantes con el tiempo, pero en general hubo mucha investigación sobre Plasmodium, leishmaniasis y esquistosomiasis.Aunque se ha diversificado, Biología Tropical aun publica sobre temas biomédicos del trópico.Conclusiones: Mientras que los países con grandes presupuestos de investigación tienen buena presencia en esta base de datos, países tropicales como Brasil y Kenia han hecho una contribución notable en el campo de la medicina tropical, dentro del cual Biología Tropical ha estado presente con un alto nivel de calidad durante siete décadas.
At the turn of the century, American and European journals specializing in tropical medicine included four large publications: Acta Tropica, American Journal of Tropical Medicine and Hygiene, Annals of Tropical Medicine and Parasitology, and Transactions of the Royal Society of Tropical Medicine and Hygiene (Keiser & Utzinger, 2005).A new study reported that the number of publications and the size of research teams increased from 1950 to 2000, but that the funding available to tropical researchers was always far smaller than funding available to their colleagues in industrialized countries (Keiser & Utzinger, 2005).
A study that included both tropical and non-tropical biomedical research, and that covered from 1995 to 2003, found that most publications on infectious diseases were from Western Europe (39 %), while the United States led in preventive medicine, public health, and epidemiology.When adjusted for country wealth, Canada, the United States, and Australia were the main publishers, while developing countries had small research footprints.In the specific field of tropical medicine, Western Europe, Africa, and Latin America had the highest output (Falagas et al., 2006).A much smaller study from that time reported that, among Latin American countries, Chile and Brazil had the strongest presence in the scientific literature (Rodriguez-Morales & Mayta-Tristán, 2009).
The practical effect that research can have on health needs to be improved, and this can be done through operational research to close the implementation gap; thus, the simple number of publications cannot be equated with the advance in tropical health, according to a later study by Zachariah et al. (2012).
More recent research has been limited to particular diseases, like leishmaniasis, giardiasis, or Zika, or to particular regions, like Asia-Pacific, Brazil, or China.Leishmaniasis, endemic in 98 countries, has been studied intensively, with 3 380 publications from 1945-1980 to 8 267 from 2001-2010 in 1 846 journals; originally, the leading producers were USA, Brazil, and India, but in later years Brazil took the lead.By population, the most productive countries are Israel and Switzerland; by gross domestic product, Nepal and Tunisia; and by per capita income, India and Ethiopia (Ramos et al., 2013).In the case of Giardia, its inclusion in 2004 in the World Health Organization's Neglected Diseases Initiative seemed to favor an increase in output (Escobedo et al., 2015).The Zika virus increased greatly from 38 publications in 2015 to 1962 publications in 2017, led by the US (47 %) (Nasir & Ahmed, 2018).
The studies about particular regions found that Asia-Pacific research, published on the journal of the same name, had a mean of 6.6 citations per article and that the most frequent keywords were malaria, dengue, apoptosis, antioxidant, rate, invasion, Anopheles stephesi, and inflammation (Musa et al., 2020).
A recent study about tropical bioresearch in Brazil found that there was an emphasis on Basic biomedical research (30 % of publications) and a shortage of Health policy and systems (7 %) and Social sciences (3 %).Additionally, the main health problems did not match the most studied subjects: research output and funding were poorly correlated with disease burden.Much money was spent on diseases like leprosy, which are now minority diseases, and less funding was given to more important diseases like leishmaniasis and schistosomiasis (Fonseca et al., 2020).
Finally, a study of tropical medicine research in China (2010 to 2019) reported 3 372 articles, most from a state disease control center; it also found that Chinese research focused on parasites and had a significant component of international collaboration, done mostly with the USA (Li et al., 2021).Similar studies have been published recently (e.g.Ho, 2021;Juang et al., 2021), centering on particular specialties.
In this article, we present the first-ever study to consider all available fields and countries on the subject of tropical medicine; additionally, this study covers, in depth, a relatively long period (the most recent three decades).

MATERIALS AND METHODS
For the overall field analysis, we used the Web of Science category tropical medicine in the Science Citation Index Expanded (SCI-EXPANDED), from here on called the database, Web of Science Core Collection, Clarivate Analytics (data updated on 19 January 2022).The 2020 journal Impact Factor (IF2020) values were from the Journal Citation Report (JCR) on 30 June 2021.According to the definition of journal impact factor, it is best to search documents published in 2020 from SCI-EXPANDED after IF2020 were presented.The SCI-EXPANDED indexes only a fraction of academic output, namely 9 531 journals across 178 Web of Science categories, and 23 of them are classified in the category of tropical medicine in 2020.
We used the relationship between the annual number of highly cited articles (TP) and yearly citations per publication (CPPyear), to understand impact trends, as done recently for emergency medicine (Ho, 2021) and anesthesiology (Juang et al., 2021).We also used six publication indicators and citation indicators as detailed by Ho & Mukul (2021).
We also analyzed the distribution of words in titles, abstracts, author keywords, and KeyWords Plus in different periods to identify changes in research focus and ranked them according to the whole study duration and 10-year study period, according to Zhang et al. (2010) and Wang and Ho (2016).
The full record of SCI-EXPANDED and the number of citations in each year for each article were downloaded into Excel Microsoft 360 and checked.Additional coding was manually performed by the functions, for example, Counta, Concatenate, Match, Vlookup, Proper, Rank, Replace, Freeze Panes, Sort, Sum, and Len were applied.The journals' impact factors (IF2020) were taken from the Journal Citation Reports (JCR) published in 2020.
In the SCI-EXPANDED database, the corresponding author is designated as the reprint author; corresponding author will remain as the primary terminology instead of the reprint author.In a single-author article where authorship is unspecified, the single-author is considered both the first author and the corresponding author (Ho, 2014).Similarly, in an individually institutional article, the institution is both classified as the first-author institution and the corresponding-author institution (Ho, 2014).
To have more accurate analysis results, affiliations were checked and reclassified.Affiliations in England, Scotland, Northern Ireland, Wales, Montserrat, Cayman Islands, Anguilla, and British Virgin Isl (British Virgin Islands) were reclassified as in the United Kingdom (UK).Affiliations in Hong Kong before 1997 were included with China (Fu et al., 2012).Affiliations in Zaire were reclassified as being from Dem Rep Congo (the Democratic Republic of the Congo) (Chuang et al., 2011).Affiliations in French Guiana and New Caledonia were reclassified as being from France.Affiliations in Sint Maarten were reclassified as being from the Netherlands.Affiliations in Greenland were reclassified as being from Denmark (Tchuifon Tchuifon et al., 2017).Affiliations in Senegambia were checked and reclassified as being from Gambia and Senegal respectively.Affiliations in USSR were checked and reclassified as being from Russia.Affiliations in W Ind Assoc St (West Indies Associated States) were checked and reclassified as being from Trinidad Tobago (Trinidad and Tobago) and the UK respectively.Affiliations in Czechoslovakia were checked and reclassified as being from the Czech Republic and Slovakia respectively (Lin & Ho, 2015).Similarly, Czechoslovak Acad Sci (Czechoslovak Academy of Sciences) was also checked and reclassified as Czech Acad Sci (Czech Academy of Sciences).Acad Med Sci USSR (USSR Academy of Medical Sciences) and Acad Sci were checked and reclassified under the heading of Russian Acad Med Sci (Russian Academy of Medical Sciences) (Chong et al., 2021) and Russian Acad Sci (Russian Academy of Sciences) respectively.Univ London London Sch Hyg & Trop Med in the UK was reclassified as London Sch Hyg & Trop Med (London School of Hygiene and Tropical Medicine).

Publications were assessed using following citation indicators:
• Cyear: the number of citations from Web of Science Core Collection in a particular year (e.g.C2020 describes citation count in 2020).• TCyear: the total citations from Web of Science Core Collection received since publication year till the end of the most recent year (2020 in this study, TC2020) (Wang et al. 2011).• CPPyear: citations per publication (CPP2020 = TC2020/TP), TP: total number of publications (Ho, 2013).
Six publication indicators were applied to evaluate publication performance of countries and institutions: • TP: total number of articles.IP: number of single-country or single-institution author articles.• CP: number of internationally or interinstitutionally collaborative articles.• FP: number of first-author articles.
• RP: number of corresponding-author articles.• SP: number of single-author articles.
Word analysis was complicated by the inclusion of low value words, such as report, conclusions, and significant, as subject indicators in the Web of Science.We manually eliminated those cases.
For the analysis of publications in the Revista de Biología Tropical, we read the titles of all articles and communications published between 1953 and 2021 (the last full year available), and extracted documents that fit the criteria listed by Gutiérrez (2002), i.e. from the following tropical medicine fields: parasitology, microbiology, hematology, clinical chemistry, pathology, genetics, toxicology, and pharmacology.

Journals:
Nearly half (14 out of 37) journals, representing 2 972 articles, did not have IF 2020 data, i.e. they were no longer listed under tropical medicine in 2020 (Table 1 1).

Output by countries and institutions:
Author affiliations were available for 195 countries, 56 % of them single-country articles, the rest was international collaboration with a total of 194 participating countries.
The CPP 2020 had an overall mean of 17 citations, with internationally collaboration leading to 21 citations, higher than single-country articles (14 citations) (Table 2).
The USA, Brazil and the UK dominated publication indicators in the database: USA with 23 % of total publications and 39 % of collaboration publications; Brazil with 22 % of single-country articles; 15 % of first-author articles; and 15 % of corresponding-author articles; the UK represented 16 % of singleauthor articles (Table 2).

Citations included in the web of science:
For the citations included in this database, and comparing the top 20 countries, other remarkable countries are Switzerland with the highest CPP 2020 for total articles, single-country articles, first-author articles, correspondingauthor articles, and single-country articles, with a CPP 2020 of 27, 27, 30, 27, and 26, respectively.Kenya had the highest CPP 2020 for total articles and internationally collaborative articles with a CPP 2020 of 27 and 29, respectively.
For the top eight productive countries, yearly publications had a steady growth for the USA; there was an intermediate growth for Brazil and the UK, and a more stable situation for India, France, China, Thailand and Switzerland (Fig. 2).The citation curves for the top cited articles, followed three main trends: most a soft up and down curve from 2000 through 2020; a few grew steadily from 2012 through 2020; and one had a clear peak around 2010 (Fig. 3).The growth trend applies to institutions and articles (Table 3, Table 4).
Concerning institutions, most (76 %) participated in inter-institutional collaborations (Table 5).The London School of Hygiene and Tropical Medicine in the UK took the leading position for three indicators with 4.1 % of articles, 5.1 % of inter-institutionally collaborative articles, and 3.5 % of single-author articles.The Fundación Oswaldo Cruz ("Fiocruz MS") in Brazil ranked top in other indicators, with 2.0 % of inter-institutionally collaborative articles, 1.6% of first-author articles, and 1.7 % of corresponding-author articles.
The WHO in Switzerland had the highest CPP 2020 for TP and RP with 33 and 37 respectively.The University of Basel in Switzerland, Seven of the top 20 productive institutes had higher CPP 2020 for their single-country articles than internationally collaborative articles, for example, the University of Basel in Switzerland, the University of California-San Francisco, and the Centers for Disease Control and Prevention in Maryland.However, the Kenya Medical Research Institute in Kenya, the Mahidol University in Thailand, and the Swiss Tropical and Public Health Institute increased their CPP 2020 by international collaboration.

Research focus and development trends:
Most articles included abstract keywords (95 %) and author keywords (55 %)."Malaria", "plasmodium falciparum", "epidemiology", and "Brazil" were the most-frequently used author keywords (1 000 articles or more).Considering the top twenty words on each list, about half of the words in the titles also appear in the abstracts; followed by around 40 % in Keywords Plus and around 35% in the author keywords (Table 5).There were also historical trends as research priorities changed: a typical new research focus was found from "Aedes aegypti", a term that was used as author keywords in 15 articles in the 1990s and in 450 articles in the 2010s.Similarly, the rank and percentage of articles with "dengue" in the author keywords went from 26 articles (rank 14 th ; 1.7 %) in the 1990s to 494 articles (rank 6 th ; 2.0 %) in the 2010s (Table 5).
A dominating subject was the epidemiology and control of malaria, caused by Plasmodium falciparum and other species of Plasmodium, particularly in children and in Brazil (Table 5).Malaria always was the most studied tropical disease, fluctuating around 240 articles per year from 1991 to 2002; after that, there was an "explosion" in the number of articles, reaching 962 articles in the year 2016 only, and with a small decrease from there to 2020, with 823 articles (Fig. 4).
Another leading subject is leishmaniasis or "Chagas Disease", caused by species of Trypanosoma transported by Phlebotomus, Lutzomyia, and others (Table 5).Leishmaniasis had under 200 articles per year from 1991 to 2006; afterwards it increased constantly and reached peaks of 423 articles in 2015 and 420 articles in 2020 (Fig. 4).
The third remarkable subject was schistosomiasis, a disease produced by trematodes, in which freshwater snails play a key role (Table 5).Schistosomiasis fluctuated between 100 and 200 articles per year in the study period; from 2007, the number of articles increased to reach 239 articles in 2020 (Fig. 4).
The human immunodeficiency virus, HIV, originated in tropical Africa and attacks the immune system of the human body, and can cause the acquired immunodeficiency syndrome, AIDS.The number of HIV and AIDS  TP: total number of articles; TPR (%): the rank and the percentage of total articles in the total number of articles; IPR (%): the rank and the percentage of single-institute articles in the total single-institute articles; CPR (%): the rank and the percentage of inter-institutionally collaborative articles in the total inter-institutionally collaborative articles; FPR (%): the rank and the percentage of first-author articles in the total first-author articles; RPR (%): the rank and the percentage of the corresponding-author articles in the total corresponding-author articles; SPR (%): the rank and the percentage of the single-author articles in the total single-author articles; CPP: number of citations (TC  articles increased slightly from 1991 to 2004, after that, there was a sharply increase to reach a plateau in 2009 (Fig. 4).The Dengue virus is transmitted to humans by mosquitoes of the genus Aedes and can potentially affect half of the world's population.Similarly, the number of Dengue articles increased slightly from 1991 to 2004; after that, there was an increase and a peak of 309 articles in 2017 (Fig. 4).
Tuberculosis is a potentially deadly disease caused by the bacterium Mycobacterium tuberculosis; it is transmitted from person to person and affects the lungs and, in later stages, other organs.Studies about tuberculosis fluctuated around 75 articles per year from 1991 to 2006; and increased afterwards to reach a peak of 207 articles in 2017 and 203 articles in 2020 (Fig. 4).
Considering the world production of articles in the eight fields of tropical medicine from 1990 to 2020, it is clear that productivity fluctuated around a stable mean from 1990 to 2000, but after the year 2000, there was an explosion in the number of publications covered by the database for Microbiology, Parasitology, Pathology and Genetics.There was little if any growth in the output for Toxicology, Pharmacology, Hematology and Clinical Chemistry (Fig. 5).

Historical trend in the Revista de Biología
Tropical: Tropical medicine publications represented nearly all of the journal's contents in the first years, with a clear descending trend from 1953 through 1969; after that, the total contributions have remained relatively stable, with the normal oscillations of any field; the 2004 surge was caused by the publication, in that year, of a special issue about tropical medicine (Fig. 6).In total, the journal has published nearly 500 articles about tropical medicine.

DISCUSSION
The increase in the number of scientific publications in recent decades, has been found in practically all previous studies that use this particular database, the Web of Science (e. g.Jozi et al., 2022;Ranasinghe et al., 2022).
However, this database only includes a small fraction of the world's science (Zhu & Liu, 2020), so we do not know if the trend reflects a real growth in the international scientific output, or just an increase in the number of journals included by the database (Zhu & Liu, 2020).525  The fact that half of the specialized journals is no longer identified as tropical medicine journals, probably reflects editors' efforts to make their journals more general, and thus, to attract more authors, readers, and citations (see Summers & Wood, 2017).
The relative impact of journals in this database seem to reflect the fact that American journals are more extensively covered in the Web of Science than European journals, and that tropical journals are poorly covered (Calahorrano et al., 2020;Zhu & Liu, 2020).
It is surprising that half of the articles are published by single institutions, because in this field, local and international collaboration are common (Elhassan et al., 2022;González-Alcaide et al., 2017).A possible reason is that, frequently, the articles that reach the Web of Science are not from tropical countries; they are produced by powerful institutions in industrialized countries, and these institutions have less need of cooperating with others to obtain the necessary resources (Sagiyeva et al., 2018).
International collaboration articles normally have higher citation rates in all countries (Ho & Mukul, 2021); well-founded megaprojects usually address health problems of general interest, for which much research is published and, thus, many citations are accumulated.
The preeminence of the USA in this field results from two factors, the enormous scientific apparatus of that country, and its excellent coverage in the Web of Science, which is based in that country.The outstanding production of Brazil reflects the fact that Brazil is the scientific powerhouse of Latin America (González-Alcaide et al., 2017).
The outstanding production of Switzerland probably results from the establishment there of the World's Health Organization (www.who.int).The leading tropical countries, Kenya, Brazil and Thailand have in common that they  are all large countries with respected academic institutions (González-Alcaide et al., 2017).These countries tend to be the ones where research continues to grow, while the stagnation of production in other large countries with tropical regions, like India, China, and Thailand, still needs to be explained.
An interesting question that does not seem to have been asked: Should scientometrics researchers use keywords in the titles, or keywords in the abstracts, or even how reliable Keywords Plus is.Our results indicate that overlap among these three keyword sources ranges from 35% to 50%, and thus, they are not interchangeable: they need to be analyzed separately.
Regarding keyword indicators of changes in scientific interest on particular diseases, the fact that malaria dominates research is not surprising because of its relative importance: in 2020, malaria caused an estimated 241 million clinical episodes, and 627 000 deaths (Centers for Disease Control and Prevention, 2022).The growth in the other diseases probably is just part of the overall growth that has characterized the Web of Science (Calahorrano et al., 2020;Nha-Trang et al., 2020;Ranasinghe et al., 2022); while the apparent reduction in interest on HIV and AIDS in recent years, probably reflects shifts in research interest as the AIDS epidemic was controlled (Wilson & Taaffe, 2017).
We cannot analyze in detail how the subjects published in the journal changed over 70 years, but the experience of one of the authors (JMN) as editor of the journal since the 1980s, is that there has been a general shift from classical fields like tropical parasitology, to other areas like genetics and pharmacology of tropical species.The same trend was found 20 years ago by Gutiérrez (2002).Despite this increase in the number of subjects, the Revista de Biología Tropical continues publishing a steady stream of tropical medicine articles until the present (Fig. 5).
In conclusion, our results indicate a twodecade long growth in the scientific productivity in all fields of tropical medicine, a growth that can only herald a better future for humanity and in which the Revista de Biología Tropical has played a role that exceeds expectations for a journal published in a country of only 52 000 km 2 .

Ethical statement:
The authors declare that they all agree with this publication and made significant contributions; that there is no conflict of interest of any kind; and that we followed all pertinent ethical and legal procedures and requirements.All financial sources are fully and clearly stated in the acknowledgements section.A signed document has been filed in the journal archives.

Fig. 1 .
Fig. 1.Historical trend for tropical medicine: number of articles and citations the Web of Science.

Fig. 2 .
Fig. 2. Historical trend for the top eight productive countries with TP > 3.000.

Fig. 3 .
Fig. 3.The citation life of the top 10 most frequently cited articles in the Web of Science; citation lifespan can reach three decades.

Fig. 4 .
Fig. 4. Historical trend for the top six topics of "neglected tropical diseases" in the Web of Science.Malaria has its own scale (on the right side of graph) because the number of publications in this field is nearly three times more than any other disease in this category.
) 24 (45) Anthropogenic environmental change and the emergence of infectious diseases in wildlife USA, UK, Australia Daszak et al. (2001) TC 2020 : the total number of citations from Web of Science Core Collection since publication year to the end of 2020; C 2020 : the number of citations of an article in 2020 only.

Fig. 5 .
Fig. 5. Historical trend for the eight fields of tropical medicine considering all articles on the subject published by the Web of Science from 1990 to 2020.

Fig. 6 .
Fig. 6.Historical trend, by number of documents, of tropical medicine publications in the Revista de Biología Tropical.
).Some changed titles and focus, for example, in 2012, Annals of Tropical Medicine and Parasitology became Pathogens and Global Health; and Annals of Tropical Paediatrics became Paediatrics and International Child Health (Table 1).Articles published in the American Journal of Tropical Medicine and Hygiene (IF 2020 = 2.345; rank 11th) had the highest CPP 2020 (a mean of 28 citations per article) while 147 articles in the Journal of Tropical Medicine (IF 2020

Table 1
The 23 journals in the Web of Science category of tropical medicine in 2020 TP: number of articles; %: the percentage of articles in total publications; IF 2020 : journal impact factor in 2020; R: IF 2020 rank in the Web of Science category of tropical medicine; APP: number of authors per publication; CPP 2020 : number of citations (TC 2020 ) per publication (TP).

Table 2
Top productive countries.CPP 2020 IPR (%) CPP 2020 CPR (%) CPP 2020 FPR (%) CPP 2020 RPR (%) CPP 2020 SPR (%) CPP TP: total number of articles; TPR (%): rank of total number of articles and percentage; IPR (%): rank of single-country articles and percentage in all single-country articles; CPR (%): rank of internationally collaborative articles and percentage in all internationally collaborative articles; FPR (%): rank of first-author articles and percentage in all first-author articles; RPR (%): rank of corresponding-author articles and percentage in all corresponding-author articles; SPR (%): rank of single-author articles and percentage in all single-author articles; CPP 2020 : number of citations (TC 2020 ) per publication (TP).

Table 3
Top 20 productive institutions in the Web of Science category of tropical medicine

Table 4
The top 15 most frequently cited articles with TC 2020 > 500.

Table 5
Top 20 author keywords in articles in the Web of Science category of tropical medicine.
TP: total number of articles.