Station 1 Dengue Fever:
Dengue fever and dengue hemorrhagic fever (DHF) are acute febrile diseases, found in the
tropics and Africa, and caused by four closely related virus serotypes of the genus Flavivirus,
family Flaviviridae. It is also known as breakbone fever. The geographical spread includes
northern Australia, Singapore, Malaysia, Taiwan, Thailand, Vietnam, Indonesia, Honduras,
Philippines, Pakistan, India, Bangladesh, Puerto Rico, Bolivia, Brazil, Guyana, Venezuela,
Trinidad and Samoa. Unlike malaria, dengue is just as prevalent in the urban districts of its range
as in rural areas. The WHO says some 2.5 billion people, two fifths of the world's population, are
now at risk from dengue and estimates that there may be 50 million cases of dengue infection
worldwide every year. The disease is now endemic in more than 100 countries. Population
movements during World War II spread the disease globally. A pandemic of dengue began in
Southeast Asia after World War II and has spread around the globe since then.
The disease manifests as a sudden onset of severe headache, muscle and joint pains
(myalgias and arthralgias—severe pain that gives it the nick-name break-bone fever or
bonecrusher disease), fever, and rash. The dengue rash is characteristically bright red
petechiae and usually appears first on the lower limbs and the chest; in some patients, it
spreads to cover most of the body. There may also be gastritis with some combination of
associated abdominal pain, nausea, vomiting, or diarrhea.
Some cases develop much milder symptoms which can be misdiagnosed as influenza or
other viral infection when no rash is present. Thus travelers from tropical areas may pass
on dengue in their home countries inadvertently, having not been properly diagnosed at
the height of their illness. Patients with dengue can pass on the infection only through
mosquitoes or blood products and only while they are still febrile.
The classic dengue fever lasts about six to seven days, with a smaller peak of fever at the
trailing end of the disease (the so-called biphasic pattern). Clinically, the platelet count
will drop until the patient's temperature is normal.
Dengue is transmitted by Aedes mosquitoes, particularly A. aegypti and A. albopictus.
Dengue may also be transmitted via infected blood products (blood transfusions, plasma,
and platelets), but the scale of this problem is unknown.
The mainstay of treatment is timely supportive therapy to tackle shock due to
haemoconcentration and bleeding. Close monitoring of vital signs in critical period
(between day 2 to day 7 of fever) is vital. Increased oral fluid intake is recommended to
prevent dehydration. Supplementation with intravenous fluids may be necessary to
prevent dehydration and significant concentration of the blood if the patient is unable to
maintain oral intake. A platelet transfusion is indicated in rare cases if the platelet level
drops significantly (below 20,000) or if there is significant bleeding. The presence of
melena may indicate internal gastrointestinal bleeding requiring platelet and/or red blood
cell transfusion. Emerging evidence suggests that mycophenolic acid and ribavirin inhibit
dengue replication. Initial experiments showed a fivefold increase in defective viral RNA
production by cells treated with each drug. In vivo studies, however, have not yet been
done. Unlike HIV therapy, lack of adequate global interest and funding greatly hampers
the development of treatment regime.
There is no commercially available vaccine for the dengue flavivirus. However, one of
the many ongoing vaccine development programs is the Pediatric Dengue Vaccine
Initiative which was set up in 2003 with the aim of accelerating the development and
introduction of dengue vaccine(s) that are affordable and accessible to poor children in
endemic countries. Thai researchers are testing a dengue fever vaccine on 3,000–5,000
human volunteers after having successfully conducted tests on animals and a small group
of human volunteers. A number of other vaccine candidates are entering phase I or II
testing. Primary prevention of dengue mainly resides in mosquito control. There are two
primary methods: larval control and adult mosquito control. In urban areas, Aedes
mosquitoes breed on water collections in artificial containers such as plastic cups, used
tires, broken bottles, flower pots, etc. Periodic draining or removal of artificial containers
is the most effective way of reducing the breeding grounds for mosquitoes.
There was a serious outbreak in Rio de Janeiro in February 2002 affecting around one
million people and killing sixteen. On March 20, 2008, the secretary of health of the state
of Rio de Janeiro, Sérgio Côrtes, announced that 23,555 cases of dengue, including 30
deaths, had been recorded in the state in less than three months. Côrtes said, "I am
treating this as an epidemic because the number of cases is extremely high." Federal
Minister of Health, José Gomes Temporão also announced that he was forming a panel to
respond to the situation. Cesar Maia, mayor of the city of Rio de Janeiro, denied that
there was serious cause for concern, saying that the incidence of cases was in fact
declining from a peak at the beginning of February. By April 3, 2008, the number of
cases reported rose to 55,000 In Singapore, there are 4,000–5,000 reported cases of
dengue fever or dengue hemorrhagic fever every year. In the year 2003, there were six
deaths from dengue shock syndrome. An epidemic broke out in Bolivia in early 2009, in
which 18 people have been killed and 31,000 infected.
1. What did you know about dengue fever before reading this article?
2. What are the signs/treatments?
3. How is it transmitted?
4. Is there treatment?
5. Can it be prevented?
6. Which areas of the world are affected today?