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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
Thirty years of research in tropical medicine: historical trends for the world
and for the Revista de Biología Tropical (1990-2020)
Julián Monge-Nájera1; https://orcid.org/0000-0001-7764-2966
Yuh-Shan Ho2*; https://orcid.org/0000-0002-2557-8736
1. Laboratorio de Ecología Urbana, Vicerrectoría de Investigación, Universidad Estatal a Distancia, 2050 San José, Costa
Rica; julianmonge@gmail.com
2. Trend Research Centre, Asia University, No. 500 Lioufeng Road, Wufeng, Taichung 41354, Taiwan ysho@asia.ed.tw
(Correspondence*)
Received 29-VI-2022. Corrected 22-VIII-2022. Accepted 25-IX-2023.
ABSTRACT
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 70th 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 partici-
pating 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 num-
ber 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.
Key words: scientometrics; research in the tropics; international collaboration on health research; contributions
of tropical science; future health issues.
RESUMEN
Treinta años de investigación en medicina tropical: tendencias históricas para el mundo
y para la Revista de Biología Tropical (1990-2020)
Introducción: La importancia de la medicina tropical no se puede subestimar, pues para fines de la década
de 2030, la mayoría de los humanos vivirán en los trópicos y necesitarán protección contra las enfermedades
https://doi.org/10.15517/rev.biol.trop..v71iS3.57584
SUPPLEMENT
2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
INTRODUCTION
This article was written in celebration of
70 years of the Revista de Biología Tropical, an
international journal published by the Univer-
sity 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 start-
ed 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 tropi-
cal 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 publica-
tions 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 jour-
nals, and the predominance of the English lan-
guage in the sample (Brennen & Davey, 1978);
however, the study was based on a handful of
American and European journals and consid-
ered only a brief period (1972-1975), making
any generalizations unwarranted.
Decades passed before another study,
which covered the period 1996-2003 and only
one European journal, provided new informa-
tion; unsurprisingly, this limited study found
that Europe produced most of the papers pub-
lished 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 con-
junto; 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 impor-
tancia 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 medici-
na tropical, dentro del cual Biología Tropical ha estado presente con un alto nivel de calidad durante siete décadas.
Palabras clave: cienciometría; investigación en los trópicos; colaboración internacional en investigación en salud;
contribuciones de la ciencia tropical; temas de salud futuros.
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schistosomiasis, public health, health promo-
tion, and health policy (Glover & Bowen, 2004).
At the turn of the century, American and
European journals specializing in tropical med-
icine included four large publications: Acta
Tropica, American Journal of Tropical Medicine
and Hygiene, Annals of Tropical Medicine and
Parasitology, and Transactions of the Royal Soci-
ety 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 Austra-
lia 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 scien-
tific 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 num-
ber 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, giar-
diasis, or Zika, or to particular regions, like
Asia-Pacific, Brazil, or China. Leishmani-
asis, 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 pub-
lications 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 empha-
sis 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 minor-
ity diseases, and less funding was given to more
important diseases like leishmaniasis and schis-
tosomiasis (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 cen-
ter; 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 coun-
tries on the subject of tropical medicine; addi-
tionally, this study covers, in depth, a relatively
long period (the most recent three decades).
4Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
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 data-
base, Web of Science Core Collection, Clarivate
Analytics (data updated on 19 January 2022).
The 2020 journal Impact Factor (IF2020) val-
ues were from the Journal Citation Report
(JCR) on 30 June 2021. According to the defi-
nition 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 medi-
cine 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 anes-
thesiology (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 iden-
tify 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 manu-
ally 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 cor-
responding 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 author-
ship is unspecified, the single-author is consid-
ered both the first author and the corresponding
author (Ho, 2014). Similarly, in an individually
institutional article, the institution is both clas-
sified as the first-author institution and the
corresponding-author institution (Ho, 2014).
To have more accurate analysis results, affilia-
tions 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). Affilia-
tions 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 Senegam-
bia 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 Repub-
lic and Slovakia respectively (Lin & Ho, 2015).
Similarly, Czechoslovak Acad Sci (Czechoslo-
vak Academy of Sciences) was also checked and
reclassified as Czech Acad Sci (Czech Academy
of Sciences). Acad Med Sci USSR (USSR Acad-
emy 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 Sci-
ences) 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).
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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
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 num-
ber 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-institu-
tion author articles.
• CP: number of internationally or inter-
institutionally 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 indica-
tors in the Web of Science. We manually elimi-
nated 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, clini-
cal chemistry, pathology, genetics, toxicology,
and pharmacology.
RESULTS
Publication output: We retrieved 69 480
articles, an average of nearly 2 400 articles per
year (1991 to 2020). For over a year, the database
did not increase the number of yearly articles
that it incorporated (1991-2004), but there was
a steady increase afterwards, only interrupted in
2018 and 2019 (Fig. 1). The citations per paper
increased from 1991 to 2003 and seemed to fall
after that date, but these results might be due to
a lag in citation processing (Fig. 1).
Journals: Nearly half (14 out of 37) jour-
nals, representing 2 972 articles, did not have
IF2020 data, i.e. they were no longer listed
under tropical medicine in 2020 (Table 1).
Some changed titles and focus, for example, in
2012, Annals of Tropical Medicine and Parasitol-
ogy became Pathogens and Global Health; and
Annals of Tropical Paediatrics became Paedi-
atrics and International Child Health (Table 1).
Articles published in the American Jour-
nal of Tropical Medicine and Hygiene (IF2020 =
2.345; rank 11th) had the highest CPP2020 (a
mean of 28 citations per article) while 147 arti-
cles in the Journal of Tropical Medicine (IF2020
= 2.488; rank 10th) had the lowest (2.2). PLoS
Neglected Tropical Diseases had the highest APP
(8.9 authors per article) and Tropical Doctor
the lowest (3.5). Infectious Diseases of Poverty
(IF2020 = 4.520) with a CPP2020 of 8.7, and an
APP of 8.2, ranked top (Table 1).
Output by countries and institutions:
Author affiliations were available for 195 coun-
tries, 56 % of them single-country articles, the
rest was international collaboration with a total
of 194 participating countries.
The CPP2020 had an overall mean of 17 cita-
tions, with internationally collaboration lead-
ing 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 single-
author articles (Table 2).
6Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
Citations included in the web of science:
For the citations included in this database, and
comparing the top 20 countries, other remark-
able countries are Switzerland with the high-
est CPP2020 for total articles, single-country
articles, first-author articles, corresponding-
author articles, and single-country articles, with
a CPP2020 of 27, 27, 30, 27, and 26, respectively.
Kenya had the highest CPP2020 for total articles
and internationally collaborative articles with a
CPP2020 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 Bra-
zil 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 %) par-
ticipated in inter-institutional collaborations
(Table 5). The London School of Hygiene and
Tropical Medicine in the UK took the lead-
ing position for three indicators with 4.1 % of
articles, 5.1 % of inter-institutionally collabora-
tive 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 arti-
cles, 1.6% of first-author articles, and 1.7 % of
corresponding-author articles.
The WHO in Switzerland had the highest
CPP2020 for TP and RP with 33 and 37 respec-
tively. The University of Basel in Switzerland,
Fig. 1. Historical trend for tropical medicine: number of articles and citations the Web of Science.
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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
the Kenya Medical Research Institute in Kenya,
the University of Oxford in the UK, and the
Mahidol University in Thailand had the highest
CPP2020 for their IP, CP, FP, and SP values, with
65, 33, 45, and 31 respectively.
Seven of the top 20 productive institutes
had higher CPP2020 for their single-country
articles than internationally collaborative arti-
cles, 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 CPP2020 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). Consider-
ing 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
Table 1
The 23 journals in the Web of Science category of tropical medicine in 2020
Journal TP (%) R (IF2020)APP CPP2020
American Journal of Tropical Medicine and Hygiene 10 409 (15) 11 (2.345) 7.2 28
PLoS Neglected Tropical Diseases 7 552 (11) 2 (4.411) 8.9 21
Malaria Journal 5 796 (8.3) 5 (2.979) 8.0 18
Parasites & Vectors 5 122 (7.4) 3 (3.876) 7.3 14
Memories Of the Oswaldo Cruz Institute 4 981 (7.2) 8 (2.743) 5.1 16
Acta Tropica 4 752 (6.8) 4 (3.112) 6.1 19
Transactions of the Royal Society of Tropical Medicine and Hygiene 4 310 (6.2) 12 (2.184) 5.9 24
Tropical Medicine & International Health 3 761 (5.4) 9 (2.622) 6.6 26
Journal of the Brazilian Society of Tropical Medicine 2 407 (3.5) 15 (1.581) 5.8 7.5
Tropical Doctor 2 340 (3.4) 20 (0.731) 3.5 5.1
Pathogens and Global Health 2 223 (3.2) 6 (2.894) 5.1 17
Journal of Tropical Pediatrics 2 197 (3.2) 18 (1.165) 4.8 11
Asian Pacific Journal of Tropical Medicine 1 958 (2.8) 17 (1.226) 4.9 8.2
Southeast Asian Journal of Tropical Medicine and Public Health 1 730 (2.5) 23 (0.267) 5.3 4.7
Leprosy Review 1 173 (1.7) 22 (0.537) 4.2 8.8
Revista Do Instituto De Medicina Tropical De Sao Paulo 1 127 (1.6) 13 (1.846) 6.0 7.7
Biomedical 1 078 (1.6) 19 (0.935) 4.8 4.4
Tropical Biomedicine 1 065 (1.5) 21 (0.623) 5.5 6.0
Journal of Venomous Animals and Toxins Including Tropical
Diseases 644 (0.93) 7 (2.831) 5.4 6.2
Infectious Diseases of Poverty 615 (0.89) 1 (4.520) 8.2 8.7
Journal of Vector Borne Diseases 595 (0.86) 14 (1.688) 5.1 6.4
Asian Pacific Journal of Tropical Biomedicine 526 (0.76) 16 (1.545) 5.2 4.7
Journal of Tropical Medicine 147 (0.21) 10 (2.488) 5.4 2.2
TP: number of articles; %: the percentage of articles in total publications; IF2020: journal impact factor in 2020; R: IF2020 rank
in the Web of Science category of tropical medicine; APP: number of authors per publication; CPP2020: number of citations
(TC2020) per publication (TP).
8Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
went from 26 articles (rank 14th; 1.7 %) in the
1990s to 494 articles (rank 6th; 2.0 %) in the
2010s (Table 5).
A dominating subject was the epide-
miology 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 Trypano-
soma transported by Phlebotomus, Lutzomyia,
and others (Table 5). Leishmaniasis had under
200 articles per year from 1991 to 2006; after-
wards it increased constantly and reached peaks
of 423 articles in 2015 and 420 articles in 2020
(Fig. 4).
The third remarkable subject was schisto-
somiasis, 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 syn-
drome, AIDS. The number of HIV and AIDS
Table 2
Top productive countries.
Country TP TP IP CP FP RP SP
TPR (%) CPP2020 IPR (%) CPP2020 CPR (%) CPP2020 FPR (%) CPP2020 RPR (%) CPP2020 SPR (%) CPP2020
USA 15 598 1 (23) 23 3 (9.5) 24 1 (39) 23 2 (13) 25 2 (14) 23 3 (12) 22
Brazil 11 517 2 (17) 15 1 (22) 12 4 (10) 21 1 (15) 13 1 (15) 13 2 (13) 13
UK 9 501 3 (14) 24 6 (3.4) 20 2 (27) 25 4 (6.0) 24 4 (6.4) 23 1 (16) 19
India 5 467 4 (7.9) 12 2 (11) 10 15 (4.1) 19 3 (6.8) 11 3 (6.7) 11 4 (7.0) 11
France 4 208 5 (6.1) 23 10 (2.2) 20 3 (11) 24 7 (3.0) 22 7 (3.2) 21 10 (2.0) 18
China 3 687 6 (5.3) 12 4 (6.0) 8.8 13 (4.5) 18 5 (4.5) 10 5 (4.7) 10 12 (1.7) 11
Thailand 3 618 7 (5.2) 18 5 (4.0) 9.1 6 (6.8) 24 6 (3.7) 15 6 (3.8) 14 9 (2.1) 19
Switzerland 3 054 8 (4.4) 27 23 (0.81) 27 5 (8.9) 27 13 (1.7) 30 13 (1.9) 27 8 (2.6) 26
Australia 2 682 9 (3.9) 23 13 (1.6) 24 7 (6.7) 22 10 (2.0) 24 9 (2.3) 22 11 (1.9) 21
Germany 2 456 10 (3.5) 20 18 (1.1) 19 8 (6.7) 20 12 (1.8) 20 12 (1.9) 19 16 (1.3) 18
Netherlands 2 277 11 (3.3) 24 27 (0.76) 18 9 (6.5) 24 14 (1.6) 23 15 (1.6) 22 7 (2.6) 12
Kenya 2 163 12 (3.1) 27 29 (0.6) 12 10 (6.3) 29 19 (1.2) 23 22 (1.2) 22 17 (1.2) 8.9
Colombia 1 950 13 (2.8) 12 7 (3.1) 7.9 26 (2.5) 18 8 (2.3) 10 8 (2.3) 10 17 (1.2) 10
Nigeria 1 929 14 (2.8) 12 8 (3.1) 9.1 27 (2.4) 16 9 (2.1) 10 11 (2.0) 10 5 (6.6) 8.5
Spain 1 828 15 (2.6) 18 16 (1.3) 18 14 (4.4) 19 15 (1.5) 18 14 (1.6) 18 39 (0.43) 18
Belgium 1 823 16 (2.6) 22 35 (0.46) 16 11 (5.4) 23 21 (1.2) 22 18 (1.3) 21 15 (1.4) 6.7
Tanzania 1 755 17 (2.5) 25 36 (0.42) 12 12 (5.2) 26 25 (0.91) 19 25 (0.87) 19 14 (1.4) 16
South Africa 1 647 18 (2.4) 18 15 (1.3) 13 17 (3.7) 20 20 (1.2) 17 20 (1.3) 16 12 (1.7) 8.4
Malaysia 1 608 19 (2.3) 12 9 (2.6) 8.7 33 (2.0) 16 11 (1.9) 10 10 (2.0) 10 21 (0.89) 13
Japan 1 557 20 (2.3) 16 19 (0.92) 14 16 (3.9) 17 16 (1.3) 16 16 (1.4) 16 45 (0.35) 13
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; CPP2020: number of citations (TC2020) per publication (TP).
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Table 3
Top 20 productive institutions in the Web of Science category of tropical medicine
Institution TP TP IP CP FP RP SP
TPR (%) CPP IPR (%) CPP CPR (%) CPP FPR (%) CPP RPR (%) CPP SPR (%) CPP
London Sch Hyg & Trop Med, UK 2 825 1 (4.1) 27 7 (1.0) 29 1 (5.1) 27 3 (1.5) 28 3 (1.6) 27 1 (3.5) 30
Ctr Dis Control & Prevent, USA 1 977 2 (2.9) 31 10 (0.86) 40 2 (3.5) 30 5 (1.2) 33 5 (1.3) 31 9 (0.62) 18
Univ Sao Paulo, Brazil 1 934 3 (2.8) 15 3 (1.8) 12 3 (3.1) 16 4 (1.4) 16 4 (1.4) 15 8 (0.89) 17
Mahidol Univ, Thailand 1 842 4 (2.7) 20 2 (1.9) 8.6 4 (2.9) 22 2 (1.6) 16 2 (1.6) 15 11 (0.58) 31
Fiocruz MS, Brazil 1 754 5 (2.5) 19 1 (2.0) 17 5 (2.7) 19 1 (1.6) 19 1 (1.7) 18 4 (1.5) 21
Univ Oxford, UK 1 327 6 (1.9) 29 42 (0.26) 32 6 (2.4) 29 20 (0.32) 45 13 (0.43) 35 7 (0.93) 27
Univ Liverpool, UK 1 105 7 (1.6) 28 15 (0.63) 22 7 (1.9) 28 10 (0.56) 24 10 (0.56) 25 3 (1.6) 18
Univ Fed Minas Gerais, Brazil 1 094 8 (1.6) 16 6 (1.1) 12 9 (1.7) 17 6 (0.77) 14 6 (0.77) 14 9 (0.62) 15
Oswaldo Cruz Foundation, Brazil 1 037 9 (1.5) 14 18 (0.53) 10 8 (1.8) 14 9 (0.58) 14 8 (0.60) 15 18 (0.43) 1.6
Inst Trop Med, Belgium 818 10 (1.2) 21 49 (0.24) 17 11 (1.5) 21 11 (0.45) 24 12 (0.53) 22 15 (0.47) 9.3
Kenya Govt Med Res Ctr, Kenya 814 11 (1.2) 32 240 (0.072) 16 10 (1.5) 33 23 (0.29) 36 35 (0.26) 32 N/A N/A
Swiss Trop & Publ Hlth Inst, Switzerland 747 12 (1.1) 20 1625 (0.006) 9.0 12 (1.4) 20 12 (0.43) 21 11 (0.56) 19 402 (0.039) 8.0
Univ Basel, Switzerland 744 13 (1.1) 19 1625 (0.006) 65 13 (1.4) 19 627 (0.025) 19 45 (0.23) 9.3 402 (0.039) 8.0
WHO, Switzerland 736 14 (1.1) 33 31 (0.32) 38 14 (1.3) 32 26 (0.26) 39 25 (0.28) 37 5 (1.3) 25
Inst Pasteur, France 694 15 (1.0) 26 26 (0.34) 22 15 (1.2) 26 19 (0.33) 30 18 (0.36) 27 24 (0.35) 10
Inst Oswaldo Cruz, Brazil 666 16 (1.0) 18 4 (1.3) 14 29 (0.85) 19 8 (0.63) 17 8 (0.60) 16 2 (2.1) 14
Univ Fed Rio De Janeiro, Brazil 665 17 (1.0) 13 20 (0.50) 8.8 17 (1.1) 14 14 (0.37) 12 15 (0.38) 12 11 (0.58) 11
University of Malaya, Malaysia 661 18 (1.0) 13 5 (1.2) 11 27 (0.88) 13 7 (0.69) 12 7 (0.73) 12 204 (0.078) 5.0
Johns Hopkins Univ, USA 640 19 (0.92) 27 58 (0.22) 30 16 (1.1) 27 17 (0.34) 30 20 (0.33) 27 24 (0.35) 28
Univ Calif San Francisco, USA 583 20 (0.84) 20 127 (0.12) 43 18 (1.1) 19 25 (0.28) 22 21 (0.33) 20 402 (0.039) 0
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 (TC2020) per publication (TP); N/A: not available.
10 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
Fig. 2. Historical trend for the top eight productive countries with TP > 3.000.
Fig. 3. The citation life of the top 10 most frequently cited articles in the Web of Science; citation lifespan can reach three
decades.
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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 popula-
tion. 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 tuber-
culosis; 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 arti-
cles in the eight fields of tropical medicine from
1990 to 2020, it is clear that productivity fluctu-
ated 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 data-
base for Microbiology, Parasitology, Pathology
and Genetics. There was little if any growth in
the output for Toxicology, Pharmacology, Hema-
tology and Clinical Chemistry (Fig. 5).
Historical trend in the Revista de Biología
Tropical: Tropical medicine publications repre-
sented 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 medi-
cine (Fig. 6). In total, the journal has published
nearly 500 articles about tropical medicine.
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.
12 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
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).
Table 4
The top 15 most frequently cited articles with TC2020 > 500.
Rank
(TC2020)
Rank
(C2020)Title Country Reference
1 (997) 15 (58) Identification of single specimens of the
Anopheles gambiae complex by the polymerase
chain reaction
USA Scott et al. (1993)
2 (814) 54 (34) The global status of schistosomiasis and its
control
Switzerland, China Chitsulo et al. (2000)
3 (706) 171 (21) The neglected burden of Plasmodium vivax
malaria
Switzerland, USA, UK Mendis et al. (2001)
4 (689) 6 (102) First report of autochthonous transmission of
Zika virus in Brazil
Brazil Zanluca et al. (2015)
5 (685) 2 (158) Refining the global spatial limits of dengue
virus transmission by evidence-based consensus
UK, USA Brady et al. (2012)
6 (641) 47 (35) The burden of malaria in pregnancy in malaria-
endemic areas
USA, Mozambique,
Spain
Steketee et al. (2001)
7 (637) 12 (62) A new consensus for Trypanosoma cruzi
intraspecific nomenclature: Second revision
meeting recommends TcI to TcVI
Brazil, USA, Colombia,
UK, France, Argentina
Zingales et al. (2009)
8 (599) 8 (96) Global numbers of infection and disease
burden of soil transmitted helminth infections
in 2010
UK, USA Pullan et al. (2014)
9 (583) 3 (146) Estimating the global burden of endemic canine
rabies
UK, France, Tanzania,
USA, Germany, Brazil,
Cambodia, South
Africa, St Kitts & Nevi,
Switzerland, Canada
Hampson et al. (2015)
10 (582) 74 (30) Quantification of clinical morbidity associated
with schistosome infection in sub-Saharan
Africa
Netherlands, Belgium,
UK, Switzerland
Van Der Werf et al.
(2003)
10 (582) 89 (27) Parasite lactate dehydrogenase as an assay for
plasmodium falciparum drug sensitivity
USA, UK Makler et al. (1993)
12 (578) 47 (35) The Alamar Blue® assay to determine drug
sensitivity of African trypanosomes (T.b.
rhodesiense and T.b. gambiense) in vitro
Switzerland Räz et al. (1997)
13 (560) 347 (16) Vivax malaria: Neglected and not benign Australia, UK, Indonesia,
Kenya, Thailand
Price et al. (2007)
14 (556) 38 (38) The economic burden of malaria USA, China Gallup and Sachs (2001)
15 (525) 24 (45) Anthropogenic environmental change and the
emergence of infectious diseases in wildlife
USA, UK, Australia Daszak et al. (2001)
TC2020: the total number of citations from Web of Science Core Collection since publication year to the end of 2020; C2020:
the number of citations of an article in 2020 only.
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Table 5
Top 20 author keywords in articles in the Web of Science category of tropical medicine.
Author keywords TP 1991–2020
Rank (%)
1991–2000
Rank (%)
2001–2010
Rank (%)
2011–2020
Rank (%)
Malaria 4 378 1 (12) 1 (13) 1 (10) 1 (12)
Plasmodium falciparum 1 829 2 (4.8) 2 (7.7) 3 (4.3) 2 (4.4)
Epidemiology 1 347 3 (3.5) 5 (4.2) 4 (4.2) 3 (3.2)
Brazil 1 130 4 (3.0) 3 (5.1) 2 (6.3) 16 (1.3)
Diagnosis 923 5 (2.4) 7 (4.0) 8 (2.9) 8 (2.0)
Chagas disease 833 6 (2.2) 11 (2.8) 6 (3.1) 11 (1.8)
Schistosomiasis 815 7 (2.1) 4 (4.6) 5 (3.2) 17 (1.3)
Prevalence 778 8 (2.1) 15 (2.0) 14 (2.1) 7 (2.0)
Trypanosoma cruzi 770 9 (2.0) 8 (3.4) 7 (2.9) 15 (1.4)
HIV 760 10 (2.0) 35 (1.0) 10 (2.3) 5 (2.1)
Children 738 11 (1.9) 10 (2.8) 13 (2.2) 12 (1.7)
Tuberculosis 725 12 (1.9) 18 (1.8) 11 (2.3) 10 (1.8)
Plasmodium vivax 709 13 (1.9) 27 (1.3) 29 (1.2) 4 (2.2)
Dengue 661 14 (1.7) 92 (0.53) 20 (1.6) 6 (2.0)
Risk factors 597 15 (1.6) 61 (0.74) 16 (2.0) 13 (1.6)
Schistosoma mansoni 597 15 (1.6) 9 (3.1) 9 (2.8) 43 (0.84)
Aedes aegypti 593 17 (1.6) 180 (0.31) 23 (1.4) 9 (1.9)
India 543 18 (1.4) 23 (1.7) 12 (2.2) 26 (1.1)
PCR 541 19 (1.4) 44 (0.88) 17 (1.7) 14 (1.4)
Visceral leishmaniasis 506 20 (1.3) 33 (1.0) 15 (2.0) 24 (1.1)
TP: total number of articles.
The fact that half of the specialized jour-
nals 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 (Cala-
horrano 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 indus-
trialized countries, and these institutions have
less need of cooperating with others to obtain
the necessary resources (Sagiyeva et al., 2018).
International collaboration articles nor-
mally have higher citation rates in all countries
(Ho & Mukul, 2021); well-founded megaproj-
ects 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 scien-
tific 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 scien-
tific 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
14 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
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. Historical trend, by number of documents, of tropical medicine publications in the Revista de Biología Tropical.
15
Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S3): e57584, agosto-diciembre 2023 (Publicado Nov. 20, 2023)
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 stagna-
tion of production in other large countries with
tropical regions, like India, China, and Thai-
land, still needs to be explained.
An interesting question that does not
seem to have been asked: Should scientomet-
rics researchers use keywords in the titles,
or keywords in the abstracts, or even how
reliable Keywords Plus is. Our results indi-
cate 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 sub-
jects 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 two-
decade long growth in the scientific pro-
ductivity 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 expecta-
tions for a journal published in a country of
only 52 000 km2.
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 fol-
lowed all pertinent ethical and legal procedures
and requirements. All financial sources are fully
and clearly stated in the acknowledgements sec-
tion. A signed document has been filed in the
journal archives.
ACKNOWLEDGMENTS
This study was financed by the authors.
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