Fast is based on commercially available ELISA-based serological

Fast means of
travel, country interdependencies, mass migration from rural to urban and from
endemic to non-endemic countries or vice versa have increased the opportunities
for contact between people of different nationalities, races and cultures. Some
of the above factors are compounded in the unique situation presented in Saudi
Arabia which is a vast subtropical country situated in the center of the
Islamic World, with unique movement of population from all over the world and
in-between these cities resulting in a unique epidemiological significance
(Khan et al. 2008).

The interest in vector-borne
diseases has recently increased worldwide. Infection with DENV produces a wide
spectrum of clinical features ranging from asymptomatic or non-specific
influenza-like undifferentiated fever in more than 50 % of infected
individuals, or viral symptoms typical DF to a severe and fatal dengue
haemorrhagic fever/dengue shock syndrome (Innis 1995; Gubler 1998; Endy et al.
2002). Thus, diagnosis of DENV infection on the basis of clinical symptoms is
not reliable, and the diagnosis should be confirmed by laboratory tests with
rapid detection and serotyping of dengue viruses.

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Diagnosis of DENV infection in
this study and in clinics and laboratories worldwide is based on commercially
available ELISA-based serological assay, a relatively simple test. However, the
assay has many limitations and drawbacks. It cannot determine DENV serotype. It
also detects crossreacting antibodies to other pathological conditions leading
to apparently false positive results at high rates of up to 42.5 %
(Wilder-Smith and Schwartz 2005).These pathological conditions include various
flaviviruses such as Japanese encephalitis (JE) virus and yellow fever (YF)
virus (Schwartz et al. 2000), tick-borne encephalitis virus, St. Louis
encephalitis virus and/or west Nile virus, in addition to the presence of
rheumatoid factor in patients with autoimmune diseases (Chanama et al. 2004).

Cases of JE and YF do not exist
in sabya or Saudi Arabia as a whole, and no subjects with previous JE or YF
immunizations were included in the study. However, many Saudis are travelling
to endemic countries for business or vacations, where they are at risk of
catching vector-borne diseases and being misdiagnosed and going unnoticed or
unreported. Therefore, false positive results, because of cross-reactivity, are
still a potential issue. We did not conduct a population-based randomized study
as we were reporting just prevalence, and therefore, a recruitment bias is
possible; however, this bias is likely to be small as sabya large hospitals
attract visitors and staff from different areas of jazan region.

No previous data on the dengue
prevalence situation in sabya are available, but a similar study conducted in
Jazan, Saudi Arabia reported prevalence of One hundred twenty four samples out
of 220 (56.4%) (Alsheikh et al., 2017).

The diagnostics of imported viral
infections such as DF is often performed with commercial tests not subjected to
regular quality control regimens and clearly demonstrated differences in
sensitivity and specificity (Groen et al. 2000).

Patients with positive IgM 4–8
days from the onset of fever and negative for PCR were most likely considered
by studies to be misclassified as having acute dengue infection (Kuno 1998).
RT-PCR-based diagnosis would be preferable for this purpose since it is
positive early during the course of the disease and becomes negative toward the
end of the febrile period when IgM becomes positive (Chan et al. 1998); thus,
the two methods can be complementary. Several real-time PCR-based methods for
the detection of DENV have been reported in the last decade. Serotype specific
real-time RT-PCR tests are able to detect and quantify DENV in the different
kinds of samples (Poersch et al. 2005; Conceição et al. 2010).The quantitative
aspect of real-time PCR is an evolutionary step in virology studies which
allows disease severity to be related to viral load. Real-time RT-PCR has
gradually replaced the virus isolation method as the new standard for the
detection of DENV. It has many advantages over conventional PCR, including
rapidity, ability to provide quantitative measurements, lower contamination
rate, higher sensitivity, higher specificity and easy standardization (Kong et
al. 2006).

The pattern of distribution of DENV serotypes detected in this study
population showed that DENV-2 was the most predominant dengue virus type, a
result which is in line with the reports of Fakeeh and Zaki (2001, 2003) and
Zaki et al. (2008) who stated that DENV-2 virus is the predominant
serotype in Saudi Arabia particularly in western Saudi Arabia since
1992.El-Kafrawy et al. (2016) showed that DEN-2 isolate from Jeddah
belongs to the Cosmopolitan genotype was most genetically related to isolates
from Pakistan circulating from 2008 to 2013.The three dengue virus serotypes
DEN-1, DEN-2, and DEN-3 are thought to be predominant in the Middle East,
especially in Yemen and Saudi Arabia (Nedjadi et al., 2015).

Nucleotide sequence of 240-bp E/NS1 junctions of 81 dengue viruses was
isolated from cases in Jeddah, Saudi Arabia from 1994 to 2006 (Zaki et al.
2008). Three serotypes (DENV-1, DENV-2 and DENV-3) were circulating, with more
than one serotype in each outbreak. DENV-1 and DENV-2 were recorded in 1994
outbreak, while DENV-3 emerged in 1997. In 2004, all three serotypes were
isolated, and DENV-1 was isolated from the summer of 2005 to early 2006 (Zaki
et al. 2008).


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