At once Increase in the Dengue Epidemic in Pakistan

Introduction:

Dengue fever (DF) has emerged as a global health problem; Dengue virus (DENV) causes epidemics throughout the subtropical and tropical regions. The disease is caused by a single stranded RNA virus. This virus belongs to the family Flavividae and has four closely related but serologically distinct types: DENV-1, DENV-2, DENV-3, and DENV-4 (Clarke, 2002). All four types are implicated in causing classical dengue fever (DF) or life- threatening syndrome, dengue hemorrhagic fever (DHF), which is characterized by abrupt onset of vascular leakage and the dengue shock syndrome (DSS) in DHF with evidence of poor perfusion, e.g. shock (Gubler, 1997, 1998). The virus is transmitted to human by bites of infected Aedes aegypti and Aedes albopictus mosquitoes (Chen and Wilson, 2004). The clinical picture ranges from relatively mild dengue fever, accompanied with characteristic symptoms such as fever, headache, retro- orbital pain, arthralgia, rash and myalgia, to severe DHF and DSS.

The primary infection with one of the four Dengue serotype provides lifetime homologous immunity, but only weak cross protection against other serotypes. Secondary infection with a heterologous serotype is implicated in the increased association with DHF/DSS as the result of antibody-dependent enhancement. The routine laboratory diagnosis of dengue virus infection is primarily achieved by RT-PCR and recently by NS1 dengue antigen Elisa. Serological diagnosis is carried out by detection of IgM and IgG antibodies by ELISA. Isolation of dengue virus in cell culture also plays an important role in dengue detection and serotyping.

Dengue fever also known as break bone fever is an infectious tropical disease caused by the dengue virus. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles. In a small proportion of cases the disease develops into the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.

Dengue is transmitted by several species of mosquito within the genus Aedes, principally A. aegypti. The virus has four different types; infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications. As there is no vaccine, prevention is sought by reducing the habitat and the number of mosquitoes and limiting exposure to bites.

Treatment of acute dengue is supportive, using either oral or intravenous rehydration for mild or moderate disease, and intravenous fluids and blood transfusion for more severe cases. The incidence of dengue fever has increased dramatically since the 1960s, with around 50-100 million people infected yearly. Early descriptions of the condition date from 1779, and its viral cause and the transmission were elucidated in the early 20th century. Dengue has become a worldwide problem since the Second World War and is endemic in more than 110 countries. Apart from eliminating the mosquitoes, work is ongoing on a vaccine, as well as medication targeted directly at the virus.

About Dengue

Dengue is a widespread mosquito-borne infection in the human beings, which in recent years has become a major, international public health concern. The disease is a serious problem in more than 100 countries in Africa, North and South America, the Eastern Mediterranean, South-East Asia, and the Western Pacific including Pakistan. Dengue fever is a sever flue like illness with fever, headache, muscle and joint pains that affects children and adults, but seldom causes death, if unattended. Dengue fever is also known as "break-bone fever". Dengue hemorrhagic fever is a potentially dangerous complication in about 1-3% of cases that begins with a sudden rise in body temperature which usually continues for two to seven days and can be as high as 40-41 degree. Blood platelets count is also decreased markedly. This can be very lethal for life due to lack of immunity. The dengue virus is passed to humans exclusively by the bite of female mosquito known as Aedes Aegypti in search of a blood meal. This mode of transmission makes the dengue virus an arbovirus (that is, one that is transmitted by an arthropod). Studies have demonstrated that some species of monkey can harbor the virus. Thus, monkeys may serve as a reservoir of the virus. Mosquitoes that bite the monkey may acquire the virus and subsequently transfer the virus to humans.

There is no way to diagnose a mosquito if he is carrying dengue virus or not. Therefore, people must protect themselves from all mosquito bites. Dengue mosquitoes breed in stored or exposed water collection systems. The favored breeding places are barrels, drums, jars, pots, buckets, flower vases, plant saucers, tanks, discarded bottles, tiers or water coolers, and other places where rain water collection is stored. Mosquito eggs develop to larva in two days.

It can be easily controlled by the various other effective methods like adopting tadpole, transgenic mosquitoes, fish and natural predators.

Dengue Fever Symptoms

After being bitten by a mosquito carrying the virus, the incubation period ranges from three to 15 (usually five to eight) days before the signs and symptoms of dengue appear in stages. Dengue Fever starts with:

 chills,

 headache,

 pain upon moving the eyes,

 low backache.

 Painful aching in the legs and joints occurs during the first hours of illness.

 The temperature rises quickly as high as 104 F (40 C), with relatively low heart rate (bradycardia) and low blood pressure(hypotension).

 The eyes become reddened.

 A flushing or pale pink rash comes over the face and then disappears.

 The glands (lymph nodes) in the neck and groin are often swollen.

 A characteristic rash appears along with the fever and spreads from the extremities to cover the entire body except the face.

 The palms and soles may be bright red and swollen.

 Fever and other signs of dengue last for two to four days, followed by a rapid drop in body temperature (defervescence) with profuse sweating. A second rapid rise in temperature follows.

Because dengue fever is caused by a virus, there is