A ccording to a study, early identification of secondary infection in a patient suffering from an acute phase of dengue infection is necessary. Dengue virus infection has emerged as a major public health concern across the globe in terms of mortality, morbidity and public health cost. According to the WHO estimates, approximately 50 million dengue fever cases occur worldwide every year and around 500, 000 cases of dengue haemorrhagic fever require hospitalisation each year with a mortality rate of 2.5 percent.
Dengue infection is the most prevalent mosquito borne Arbovirus infection in tropical and sub-tropical regions of the world and has been reported as endemic in more than 100 countries in Africa, America, Eastern Mediterranean, South East Asia and Western Pacific. The principle vector is a day-biting domestic mosquito Aedes aegypti; although a second dengue vector Aedes albopictus has been shown to be responsible for transmission of dengue in Asia.
In Karachi the first confirmed epidemic of dengue infection was reported in 1994.
Four antigenically different serotypes of dengue virus (DEN 1-to-DEN 4) have been identified. In Karachi during 1994 outbreak, DEN 1 and DEN 2 were isolated, whereas in 2005 outbreak, DEN 3 was detected. Co-circulation of DEN 2 and DEN3 was identified during 2006 outbreak in the city.
The Abbasi Shaheed Hospital is among the major hospitals in public and private sector that provides tertiary care facilities in Karachi. For the past few years, serological diagnosis of dengue infection has been performed by rapid ICT assay. A cross-sectional observational study was conducted at Abbasi Shaheed Hospital, Karachi from July 2008 to January 2009 to determine the frequency of ICT seropositive cases and to evaluate the role of rapid ICT test as a diagnostic aid in patients with suspected dengue infection. In dengue endemic areas like Karachi, serological evidence is useful to provide information on epidemiology of the disease which is essential to plan necessary measures to control and prevent dengue infection.
The study revealed that early identification of secondary infections during an acute phase of illness is valuable for the clinician due to higher risk of progression to life threatening dengue haemorrhagic fever and dengue shock syndrome and therefore of utmost importance to reduce the fatality rate.
In Karachi, the cyclic epidemic pattern of dengue infection has been observed in post monsoon season. Relative increased humidity of post monsoon season has been shown to be the contributing factor for increased dengue propagation in Aedes aegypti. The peak incidence of dengue infection is between the period of August and November, highlighting the months suitable for dengue transmission and need of effective pesticide spraying after rain fall. Demographic characteristics like age distribution and gender differences are important for the successful planning of public health programmes and effective control of communicable diseases.
Differences in infection rates and severity of disease among males and females are reported in few hospital based studies from other countries. Studies from South America report almost equal male to female ratio, whereas studies from India and Bangladesh showed predominance of males. The present study found nearly twice the number of male patients compared to female in clinically diagnosed dengue fever (both ICT reactive and ICT non-reactive). The lower infection rates in females of Asian community might be attributed to lower reporting rate and the fact that they remained stationed at home and are less exposed to this vector born infection.
Some studies from Asia revealed higher case fatality rate (CFR) among females despite high infection rate in males. In contrast, of four deaths in our study sample two were females. Children and adolescence have been reported to be the predominant group in Southeast Asia including some parts of India. In the present study data of both ICT reactive and non reactive cases of dengue fever revealed pre dominant involvement of young adults in the 13-33 years age group. This finding is consistent with another local study from Karachi and studies from other endemic countries.
