DISCUSSION
Differing information regarding the origin of the DENV virus maintains
the constant search for data that can provide a better understanding of
this disease, which is one of the most important and also neglected in
the world. Phylogeographic studies can help to understand the dispersion
and evolution of a virus, as well as understand the dynamics of
transmission and thus help to improve strategies for control and
prevention of the dengue virus 21,22. The present
study reviewed the molecular evolution of dengue virus serotypes
worldwide with 1,581 WGSs with sampling dates from Jan/1944 to Jul/2022.
The results demonstrated that the tMRCA of DENV-1 was 1884 in Southeast
Asia, DENV-2 was 1723 in Europe, DENV-3 was 1921 in Southeast Asia, and
DENV-4 was 1876-03-28 in Southeast Asia.
DENV infections represent a major health and economic problem worldwide,
and although most cases are asymptomatic or induce a mild degree of
illness, the WHO estimates that around 500.000 people per year who
develop severe dengue syndrome, need hospitalization23,24. With slave trade vessels and trade routes, the
world’s main urban vector of the dengue virus, A aegypti ,
originated in West Africa and arrived in Europe at the end of the 17th
century 9. Although there is a strong line of
assertion that dengue originated in Asia, between the 19th and 20th
centuries, our data point to the appearance of dengue in Spain in 1682
and later in 1838 in Indonesia. Break-bone fever or “Quebranta huesos”
was a popular name do describe the disease and was used by a doctor from
Puerto Rico when he described a febrile illness in 1771, and in 1801 the
Queen of Spain, María Luisa de Parma, mentioned in a letter that she was
suffering from a disease that caused bone and joint pain, presence of
jaundice, hemorrhage, and fever. These symptoms are clinically
consistent with those of dengue and this statement reinforces that the
onset of dengue originated in Spain [23,24].
Stica et al., (2021)27, used Bayesian evolutionary
analyses and estimated the emergence of DENV1 in 1660s, and the time of
divergence of the other DENV1 genotypes from the Malaysian wild isolate
in 1886s 27. Regarding the origin of DENV2, there are
studies that suggest the common ancestor of DENV2 may have emerged even
earlier than previously thought, possibly in Asia or Africa. A
phylogeographic analysis conducted by Wei and Li (2017)28 indicated that the most recent common ancestor
dated back to 1917 28. However, Walimbe
(2014)29 showed that DENV-2 diverged from the sylvatic
genotype around 1860, while Costa et al. (2012) dated the time to the
most recent common ancestor to 338 years ago (1674)29,30. An analysis by Stica et al.
(2022)27 estimated that the epidemic genotypes of
DENV2 diverged from wild isolates in the year 1733, suggesting an
earlier origin of the vírus and in this sense, our study corroborates
the authors’ findings and the date indicated for the emergence of DENV2
was 1723 in Europe 27. Costa et al.
(2012)30 found the time to the most recent common
ancestor of DENV3 to be in 1904, while in our analyses, we found an
approximate date of April 12, 1921 (HPD95%: May 25, 1918; March 13,
1924). In relation to DENV-4, according to our analysis, the molecular
origin is estimated to have emerged between the years of 1865 and 1899,
even before serotypes 1 and 3. Costa et al (2012)30determined the time to the most recent common ancestor to be 203 years
ago (1809). Our analyses are consistent with the findings of Costa et
al. (2012)30 regarding the oldest DENV serotype,
although the authors found the TMRCA of DENV-2 dating back to 1674 while
in our study, it was estimated to be 1723 30.
DENV1 has 5 distinct genotypes, and Villabona-Arenase et al. (2013)31, demonstrated that genotypes I, IV and V are the
main genotypes worldwide 8,31. In 2016,
Bruycker-Nogueira 32 performed a phylogeographic
analysis of the dengue virus in the Americas from 1962 to 2014. DENV-1
genotype V seems to be the most prevalent in the last 40 years and,
among the 5 genotypes until now classified and, in the Americas it
represents 99% of prevalence, in Africa it accounts for 43% and in
India/Nepal/Bangladesh, 100%. The authors also showed that the current
diversity of DENV-1 in the Americas was due to the introduction of
genotype V from India in the early 1970s and again in the early 1980s32. DENV1 was first reported in 1943 in French
Polynesia and Japan, followed by reports in Hawaii in 1944 and 1945,
with increasing reports in the Asian region from the late 1950s. The
first introduction of DENV1 in Africa was estimated to be in 1946,
following its introduction from South Asia to West Africa33 but the first report of DENV1 occurred in 1984 in
Sudan 9. In Colombia, DENV-1 was introduced around the
1970s and was related to the virus circulating in the Lesser Antilles34. In the 1980s and 1990s, Brazil, Mexico, and Puerto
Rico began to present continuous reports of DENV-1 9.
Dengue virus serotype 2 (DENV2) is known to have five main genotypes,
labeled I-V and, the most recent data suggest that serotypes 1 and 2 are
the most prevalent in the world 8,35,36. Our analyses
revealed that the dengue virus serotype 3 (DENV3) arrived in Southeast
Asia in 1921 but Araújo et al., 2009 37 estimated that
it arrived around 1890, and Twiddy et al. (2003) 38estimated it to be in 1900. This difference could be justified due to
our dataset covering a longer period of analysis (January 1944 to July
2022), with more data available, in addition, to the difference between
the methodologies used by the authors (partial genomes analysis and
maximum likelihood tree method) and ours (complete genomes analysis and
maximum clade credibility tree method).
DENV-3 was first reported in the Philippines and Thailand in 1953 and it
presents 5 previously described genotypes. Genotypes I and II consist of
strains isolated from the Asian region, while those of genotype III are
distributed in Asia, the Caribbean, the Americas, and Europe35. In Africa, the oldest known sequence of DENV-3
comes from Mozambique in 1985, but its occurrence has been sporadic. In
the Americas, the first reports emerged in 1963 in Puerto Rico, but most
other countries did not have occurrences until the end of the 1980s.
Since 1990, there have been records of DENV-3 occurrence in China,
Vietnam, Cambodia, and Singapore 9.
DENV-4 has 4 main genotypes (I, II, III, and sylvatic) and exhibits
greater conservation in its genome compared to the other DENV serotypes35,39,40. The first strain, DENV4-1, was detected in
1956 in the Philippines and was the exclusive strain of transmission for
20 years, where it evolved and spread to Thailand, Cambodia, Australia,
and China before diverging into other genotypes 40.
Alfsnes et al. (2021)33 showed that DENV-4 emerged in
West Africa in the early 1950s, then this would be the earliest reported
occurrence of the DENV-4 serotype33.
The circulating DENV
rapidly changes its genome through random mutations that accumulate over
time, especially due to the co-circulation of multiple serotypes. These
mutations can lead to the emergence of new serotypes, as was the case
with DENV5, the fifth serotype recently discovered 41.
In 2007, in Malaysia, a dengue outbreak hit the state of Sarawak and
samples from a severe case, which had been classified as dengue 4, did
not respond to diagnostic tests for confirmation of the four know
serotypes. In 2013, it was announced that, after genotyping, it was
discovered that this case belonged to a new serotype, DENV542,43. This serotype only circulates in the forests of
Sarawak, among non-human primates and follows the sylvatic cycle, and is
genetically similar to the other 4, suggesting that the ancestral origin
is shared and has so far been associated with only one outbreak,
indicating a low transmission rate 14.
In recent years, the
global incidence of dengue fever has been increasing, and the
notification of the different types of dengue virus (DENV) may be
inaccurate due to various types of biases, especially in areas with
limited resources for virological diagnosis. Therefore, the reported
numbers of cases of the disease may not reflect the true extent of its
occurrence 9 OPAS. Through computational modeling, it
is estimated that over 390 million dengue infections occur annually, of
which 96 million manifest the severe form of the disease44. Phylogeographic analysis is a valuable tool to
understand the relationship between the phylogenetic and geographic
relationships of dengue virus (DENV) serotypes, which can provide
important information about the genetic diversity of the disease over
time and space. Additionally, phylogeographic analysis can help
understand the transmission dynamics of the virus both within a
particular region and between different regions, allowing healthcare
professionals to take more effective preventative and control measures.
This information can also be used to identify when a new strain of DENV
emerged and how it circulates within and outside the region even before
surveillance systems can detect its presence, enabling a faster and more
effective response to dengue epidemics 27,45,46.
While waiting for the development of a vaccine, prevention and control
measures should be adopted, such as vector control, healthcare services
with a good team and adequate infrastructure, which includes raising
awareness among healthcare professionals and effective measures in
dengue diagnosis 47. The reduction of breeding sites,
with targeted elimination of vector populations using insecticides and
larvicides through spraying in the sources, around houses with positive
cases of the disease, and also mass outdoor spraying in neighborhoods or
cities, serves as a measure of prevention and control of the disease48. Basic sanitation management and proper management
of water storage containers and waste disposal are essential in vector
control, which is closely linked to the concepts of environmental
hygiene. These integrated actions for vector control can interfere not
only in the transmission of the dengue virus but also in other diseases
that depend on this environmental control, such as diarrhea and malaria.
However, in the context of social vulnerability, in environments
affected by ongoing humanitarian crises, in the process of recovery or
regions that host refugee populations, these environmental approaches
are hardly applied due to rapid population expansion, leading to a lack
of sanitation infrastructure in these places, which results in an
increase in the incidence of diseases in susceptible individuals49.
Some studies have suggested vector control at the molecular level. Lopez
et al. (2021)50 observed that dengue virus particles
interact with proteins in the Aedes aegypti vector (AeSNAP and
ATPase), suggesting that these influence DENV viral dissemination and
that further studies are necessary to clarify these findings so that
anti-vector measures can target specific mosquito molecules,
representing a promising alternative measure compared to current methods50.
Urgent actions are necessary to control dengue, which is expanding,
where it is possible to generate innovative and effective tools in
vector control in urban populations, mainly protecting high-risk areas.
The natural evolution of DENV occurred through purifying selection,
meaning that most changes in amino acids were deleterious and quickly
purified, leading to an evolution of viral proteins that caused an
increase in fitness for infection between mosquitoes and primates35. The selection pressure, such as from the immune
system of both the human host and the mosquito host, as well as the
interaction between different serotypes, leads to new variants of the
virus 27.
The rate of variability of DENV is heterogeneous, meaning that a
different genotype within the same serotype may have a higher or lower
rate of variation. As a result, we can understand that phenomena such as
population dynamics and viral epidemiology are directly linked to this
heterogeneity 51. Li et al. (2022)52 pointed to the existence of variation in the
predominant selective force among different serotypes of the dengue
virus, evidenced by the identification of positive selection in several
proteins, including structural (capsid, membrane and envelope) and
nonstructural NS2A, NS3A, NS2B, NS4A, and NS4B. In addition, the authors
observed that these selective forces vary between continents in some of
the analyzed genes, providing valuable information about the evolution
of dengue virus serotypes 52.
Dengue cases have been reported in African countries since the 19th
century. The four serotypes have already been isolated on the African
continent, with DENV2 and DENV3 causing most of the
epidemics48.
One of the causes of underreporting has been the identification of
febrile illnesses and their treatment as malaria instead of dengue, as
presumed at the time of medical care 53. Isolated
dengue outbreaks are frequently recorded in Africa, occurring mainly in
the eastern region. However, due to the precarious surveillance
infrastructure and under-recognition of the disease, cases are not
properly characterized. These available data make it difficult to
determine whether African populations are truly vulnerable to dengue in
the same proportions as populations in Asia and Latin America53.
Therefore, some studies report possible hypotheses for the low dengue
incidence in Africa, suggesting that the African population may be less
vulnerable to dengue infection than other ethnic groups. Race, as
suggested in some studies, may be a factor influencing resistance to
infection, where black patients showed greater resistance to the
disease. In epidemics reported in Cuba (1981) and Los Angeles (1998),
white ethnic groups showed greater susceptibility to the disease,
particularly in the development of severe forms and even death. Genetic
polymorphisms in cytokines and coagulation proteins have been proposed
as mechanisms of resistance in black individuals, but further studies
are needed to determine this fact 53,54.
The main vector of dengue transmission, the Aedes aegyptimosquito, originated in Africa and spread to other continents. Other
species also contribute to the transmission of the disease, such asAedes albopictus , Aedes african us, and Aedes
luteocephalus 53. Another hypothesis for the
underreporting of dengue in the African region is that the transmission
vectors A. aegypti and A. albopictus have shown lower
susceptibility to all 4 DENV serotypes in controlled laboratory
environments. This reduced efficiency of the vector for disease
transmission may explain the lower disease prevalence rates in the
African region than expected, although further studies are needed to
explain this phenomenon 53,55.
Dengue transmission is highly dependent on climatic factors, and
attention has been focused on predicted climate changes that may
influence the spread of the disease to currently unaffected areas.
Dengue is rare in Europe, but cases have been reported in Croatia and
France, raising concerns about the potential emergence of dengue in
Europe, especially with the predicted climate changes. The concern is
that the main dengue vectors are already present in Europe, such asA. albopictus , a secondary vector of the disease found in many
European countries including the Netherlands, Switzerland, Russia,
Slovenia, France, Spain, and Greece. However, the presence of the vector
does not necessarily mean that the region has the disease, as a
combination of factors including the presence of the virus in the
population, hosts, vectors, and appropriate climatic conditions
(temperature, humidity, precipitation) are required for transmission.
Nevertheless, the presence of the vector in the region increases the
risk of dissemination if the combination of factors becomes favorable,
as indicated by the indicators 47,56.
In conclusion, the dengue disease has had a significant impact on global
health worldwide and the present study provides an overview of the
molecular evolution of dengue virus serotypes, showed the origins of
serotypes DENV-1 - DENV4 (DENV-1 in 1884 in the Southeast Asia, DENV-2
in 1723 in Europe, DENV-3 in 1921 in Southeast Asia, and DENV-4 was 1876
in Southeast Asia). The molecular origin of the dengue virus was in
Spain in 1682, later it was disseminated in Asia (Indonesia in 1838) and
Oceania (Papua New Guinea in 1844). After this period, the virus spread
to Asia (Malaysia; India, and China in 1890) and in North America (USA
in 1895). In South America, it was first disseminated to Ecuador in 1897
and then to Brazil in 1910. During this same period there were
disseminations to American countries such as the USA, Mexico, Puerto
Rico, Cuba, Haiti, Nicaragua, El Salvador, Costa Rica, Panama, Jamaica,
Trinidad and Tobago, Venezuela, French Guiana, Colombia, Peru, Paraguay,
and Argentina. In the African continent this virus was disseminated in
Senegal, Mauritania, Guinea-Bissau, Ivory Coast, Burkina Faso, Benin,
Cameroon, Gabon, Kenya, Djibouti, Somalia, Angola, Tanzania, and
Mozambique. In Europe low dissemination occurred and this process was in
Spain, France, Italy, Germany, and Portugal. Dissemination in Middle
Eastern countries has been detected in countries such as Saudi Arabia
and Pakistan. In Asia, dengue virus was detected in Indonesia, India,
Sri Lanka, Nepal, Bangladesh, Myanmar, Laos, Thailand, Vietnam,
Malaysia, Taiwan, Philippines, Singapore, China, South Korea, and Japan.
In Oceania was detected in Papua New Guinea, Australia, New Caledonia,
Fiji, Tonga, Samoa, Cook Island, and French Polynesian.