By now dengue is
a known name to majority of Pakistanis, thanks to 2011 outbreak. After winters
each year we start hearing buzzing of little mosquitoes. Annoying as they may
seem, these tiny creatures stir a sense of fear in us. It is November and we
are still getting cases of dengue infection mainly from Karachi
and Rawalpindi .
Dengue infection is caused by dengue virus which has four different types
circulating in blood of humans (serotypes 1-4). Serotype-5 of dengue infects
non-human primates only. Dengue infection has three manifestations, namely,
dengue fever (DF), dengue hemorrhagic fever (DHF) and dengue shock syndrome
(DSS). World Health Organization (WHO) has updated case definitions for dengue
infection to classical dengue and severe dengue cases. Dengue fever is febrile
acute infection where the patient may or may not experience symptoms. Almost
97% of dengue infections are asymptomatic i.e., no visible symptoms appear to
identify the infection. Patient may feel lethargy and fever which are vague
signs to characterize this infection. Dengue hemorrhagic fever is the severe
form of infection where plasma leakage occurs that can cause failure of organs
and may lead to dengue shock syndrome.
Many sporadic
cases have been reported due to all four serotypes of dengue virus in our
country. Notably, the circulating dengue types 2 and 3 are of Sri Lankan and
Indian origins. Serotype-2 remains predominant in Pakistani region (Z. Fatima et al. BMC Microbiol. 11, 200; 2011).
This infection
is spread through female mosquitoes of Aedes
family. Female mosquitoes need a protein in development of their eggs. They get
that protein from blood of primates. To bite a primate these female mosquitoes
have special mouth parts which are not present in male mosquitoes. Male
mosquitoes mainly feed on plant material. Aedes
albopictus is a native species of South East Asia that transmits dengue
virus but intensity and spread of dengue is attributed to spread of Aedes aegypti in our region(S. B.
Rasheed et al. Public Health 127,
11-17; 2013). Since A. aegypti is
more adaptable than A. albopictus,
the former species has broadened the area of dengue infected regions to
provinces of Khyber Pakhtoonkhawa, Punjab and
Sindh. Nevertheless A. aegypti is the
main carrier of dengue virus. A changed trend in infections from Americas is
observed for our society. Mostly adults and males are infected with dengue
virus in Pakistan due to
different cultural and daily routine from South America
(Z. Fatima et al. Public Health 127,
875-877; 2013). Our house holds remain a bit safer than our outsides may be due
to the breeding of Aedes in open
surroundings.
Again this year Karachi is hit by dengue
virus as she has been in the past. As per reports issued by Dengue Prevention
and Control Program Sindh, this year around 2900 cases are reported from Sindh
province out of which more than 2830 cases are from Karachi. Since the report
of first death due to dengue infection in Karachi
in May, this toll has increased to eight.
Port city of Karachi can be taken as an important city while plotting
history of dengue in Pakistan .
It was Karachi
from where the first outbreak of dengue hemorrhagic fever was documented in
1994. This happened due to dengue serotype-2. Dengue serotype-3 was also first
time reported from Karachi in 2005 in Pakistan . After
that it was isolated from other provinces and regions of our country.
A recent study
by our group traced back introduction of dengue virus serotype-2 in Pakistan . This
virus was introduced twice in our region, first in late 1980s from India in south of Pakistan ,
and then in 2000 from Sri Lanka
in Punjab (M. Akram et al. Virology Jol. 12, 148; 2015). This first introduction of
dengue virus was mainly in the region of Karachi
and we can see that it proved significant since this region of Pakistan became endemic long before other
regions of Pakistan .
But the later event was more powerful in Punjab
and has successfully logged dengue infection here. Since 2006 almost 40,000 cases were reported
by federal and provincial health departments in Punjab
with more than 528 deaths. 83% of these cases were reported during and after
2010.
Each year Karachi reports a large
number of dengue infected cases. If we probe more into this matter, we see that
Karachi is a
well suited place for breeding of Aedes.
The city is a metropolis and the most populated city of Pakistan .
Climate is mainly humid and temperatures remain high till November. She is the
financial hub and travelling to and from this city is frequent. These factors
are ideal for growth and spread of mosquitoes. Floods of 2010 may have enhanced
the transmission of dengue infection here. Unhygienic conditions play an
important role in spread of mosquito. One of our common practices is to leave
utensils, tires, debris, or any other sort of container open in the environment
where water becomes stagnant. This is the ideal breeding ground for Aedes mosquitoes.
Control of
dengue infection should be both at medical and surveillance level. This year
many reports surfaced in which lack of funds in Sindh were highlighted.
Inspection of dengue spread in Karachi
was halted due to shortage of funds, human resources or dengue kits. Municipal
department had to stop fumigation campaign for weeks which could have added to
spread of Aedes mosquito.
Despite of its
horrors, this infection can be controlled effectively by following few steps as
rituals. One of the most important one is to keep our surroundings dry throughout
the year. We people must take notice of any puddle or container in our vicinity
to keep mosquitoes away. Sprays should be used to kill any larvae and/or adult
flying mosquito. Care must be taken to cover oneself properly especially during/after
monsoon and rainy season. Mosquito repellents and coils must be used at homes. The
biggest step to prevent any dengue infection becoming an epidemic is to keep
our surroundings dry. This one step together with use of mosquito/larvae
killing sprays can prove to be beneficial to control spread of dengue in our
society.
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