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Dengue fever

from Swahili: denga - cramp
Synonyme: DHF
German: Dengue-Fieber

1 Definition

The Dengue hemorrhagic fever or short DHF is an infectious tropical disease. It is caused by arboviruses of the genus flavivirus. The virus is transmitted by the mosquito.

In Germany the DHF is a notifiable disease.

2 ICD10-Codes

  • A90: Dengue fever (classical dengue)
  • A91: Dengue hemorrhagic fever

3 Pathogen

The disease is caused by the dengue virus. It is a single strand RNA virus (ss(+)RNA). There are four DEN serotypes (DEN-1 to DEN-4). The serotypes appear in different endemic regions and there is no cross-immunity between them.

The virus reservoir is made up of humans, primates and mosquitos. An infected mosquito can transmit the virus to its descendants through its eggs. This allows the virus to survive dry and cold peroids.

4 Transmission

The DHF is transmitted through vectors of the genus stegomyia. The most prominent members being the yellow feaver mosquito and the tiger mosquito. After the mosquito bite, the viruses first interaction is with dendritic cells of the immune system. Within these primary target cell the virus is able to reproduce and can then spread from there to the rest of the organism.

The transmitting mosquitos reproduce in stagnant water and even small puddles and water filled canisters (i.e. open can) are a sufficient environment for the larvae. This maked it possible for the mosquitos to also inhabit cities.

Transmission from human to human is possible through transfusion of contaminated blood products. In region where the dengue fever is endemic this has lead to the discussion of a systematic screening of blood donors.

5 Epidemiology

About 50 million people per year suffer from the dengue fever. The incidence has quadrupled in the time from 1986 to 2006. The majority (>90%) of infected patients are children. Lethality is somewhere between 2-5%. For newborns and infants this rate is considerably higher.

The regional focus of the dengue fever are the tropical and subtropical regions of central Africa, Latin America, India and southeast Asia. The disease is also present in the southern parts of the USA (Texas). Migration and tourism have lead to cases of the dengue fever occurring in Europe. In 2004 there was a total of 121 cases reported in Germany (by the Robert Koch Institute (RKI). That shows that dengue fever should be considered for people returning from a tropical location with fever in the absence of malaria.

In 2012 a large outbreak of the dengue fever occurred in Madeira. It was rated by health organizations as the largest dengue endemic in Europe since the 1920s.

The progressing regional spreading of the vector means that the dengue fever should be expected to become endemic in Europe in the medium-term timeframe.

6 Symptoms

Following a 2-7 day incubation period the disease presents with a sudden onset of flu like symptoms. Including:

After 4-5 days a mobiliform rash presents along with a swelling of the lymph nodes. The classic dengue triad consists of fever, rash and headaches, joint pain or aching limbs.

7 Disease progression

In most cases the initial infection with dengue has an uncomplicated progression. In about 90% of the patients no or only mild symptoms are experienced. The DHF has a much more dangerous progression. It is most likely caused by a secondary infection with a different serotype of the dengue virus.

8 Diagnostics

The definite diagnosis of dengue fever is made through either verification of antibodies or direct viral proof (RT-PCS, NS1-antigen test). It can be achieved between the 4th and 7th day.

9 Differential diagnosis

10 Treatment

The previous wide spread use of insecticides against the transmitting mosquitos has been discontinued because of its environmental effects. Individual households can prevent mosquito reproduction by covering up or removing all liquid surfaces.

Recently there have been attempts to biologically combat the mosquitos using a larvazid that is harvested from the thuringiensis isrealensis bacterium. Its effectiveness has not been proven yet.

11 Prophylaxis

Individual prophylaxis is the same as for malaria: Repellents (especially DEET) and insect sprays. The skin should be covered with bright, thick, long-sleeved clothing. When sleeping mosquito nets provide a sufficient barrier. It should be noted that the aedes mosquitos, contraty to the anopheles mosquito are also active during the daytime.

12 Therapy

As of 2016 there has been no immunization approved in Germany. There is however a candidate in the phase III of its clinical study. There is no antiviral medication for dengue-fever, only symptoms can be treated.

In the first days of the infection an appropriated substitution of liquids has to be ensured intravenously. The substitution is titrated to produce about 0,5-1 ml/kg/hr urine, stabile vitals and regular hematocrit. The increased risk of bleeding means that invasive medical procedures such as a nasal tube, intra muscular injections arterial taps should be avoided.

Fever peaks can be buffered through leg compresses. The pain is mostly managed with paracetamol. NSRA such as ASS are contraindicated because of their anticoagulative effects.

13 Vaccination

The first vaccine CYD-TDV from Sanofi was approved in December 2015 in Mexico. It is a tetravalent live vaccine. So far studies have shown them having an immunization effectiveness of 56-65%. Approval in Germany was supposed to happen in 2016.

A major problem in the vaccine development is that all 4 serotypes should be covered to avoid an increase in HDF cases.

14 Sources

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