Dengue fever is an infection caused by dengue viruses, of which there are four different serotypes known to infect humans.
The disease is transmitted by mosquitoes. After infection, a person is immune only to that particular type.
Further infections with a different type have a higher chance of severe or complicated dengue also known as dengue haemorrhagic fever (DHF).
According to the World Health Organization (WHO) the number of cases reported worldwide has grown dramatically in recent decades.
A recent estimate of 390 million dengue infections occurring globally per year, with 96 million presenting with symptoms, underlines the potential impact of dengue on populations in endemic regions (TravelHealthPro).
There have been 55 cases of dengue fever notified year-to-date in South Australian, from travellers, compared with 36 cases reported for the same period last year (SA Health).
Transmission and Risk
Aedes aegypti is the principle mosquito vector associated with dengue transmission and is closely associated with humans and their dwellings. A. aegypti mosquitoes breed in water containers (including buckets used to collect rainwater, cisterns, toilets and tyres) and rest inside in cool, dark rooms.
They are most active during daylight hours, when they feed from dawn to dusk, but can bite at night in well-lit
areas. Only the female mosquito transmits the dengue virus. Australia - Towns in north Queensland that have Aedes aegypti are prone to outbreaks of dengue when the virus is brought in by travellers.
Between outbreaks, Australia is free of dengue fever, but continuous efforts to control the mosquitoes are needed to keep it that way. Local Aedes aegypti are not normally infected with the virus, unless they have bitten a person sick with dengue.
Tropical and Sub-tropical Climates - Dengue occurs in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.
Dengue is endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. During 2010, locally acquired cases were reported in Croatia.
In France, sporadic cases of local dengue transmission have been reported since 2010.
The chance of contracting dengue is determined by several factors, including destination, length of exposure, intensity of transmission and season of travel.
Risk is thought to be higher during periods of intense mosquito feeding activity (two to three hours after dawn and during the early evening).
Travellers who spend long periods in endemic areas (such as expatriates or aid workers) are at increased risk. However, even short-term visitors may be exposed.
People get sick three to fourteen days after a bite from an infected dengue mosquito.
Dengue does not spread directly from person to person.
After biting an infected person it takes 8 to 12 days before the mosquito can infect other people. The mosquito remains infectious for life.
In about 75 percent of cases there are no symptoms.
Typical symptoms may include:
- Sudden onset of fever, extreme tiredness
- Intense headache (especially behind the eyes)
- Muscle and joint pain (ankles, knees and elbows)
- Loss of appetite, vomiting, diarrhoea, abdominal pain, a metallic taste
- Flushed skin on face and neck, fine skin rash as fever subsides
- Red rash on arms and legs, itching, peeling of skin and hair loss
- Minor bleeding (nose or gums) and heavy menstrual periods.
The illness lasts up to a week. In some cases, fever and possibly worse symptoms may return for another two to three days. Dengue ranges from mild or unnoticed (more often in children), to severe or even fatal cases.
Complications include shock and haemorrhage.
Recovery is sometimes associated with prolonged fatigue and depression.
Treatment of dengue and severe dengue is supportive (i.e. aims to manage the symptoms and complications of the infection).
Most infections are self-limiting, with improvement in symptoms and rapid recovery occurring three to four days after the onset of the rash.
Lifelong immunity to the infecting dengue virus serotype occurs in those who recover.
However, infection with one stereotype does not confer immunity to the other three serotypes or to other flaviviruses.
Travelling to a place with dengue - avoid mosquito bites:
- Wear long sleeved, light coloured clothing, and cover your feet.
- Use insect repellent containing DEET (diethyl toluamide) or picaridin and reapply according to the label.
- Speak with a Travel Health Practitioner for more information.
South Australian Health
Catherine Keil is a Nurse Practitioner Travel Health and Immunisations based at Angaston Medical Centre.
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