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A Social Issue Neglected Tropical Diseases and Three Major Infectious Diseases

Dengue Fever

An infected mosquito, usually Aedes aegypti or Aedes albopictus, transmits the dengue virus through bites to humans, thereby causing dengue fever. People with the infection either have no symptoms or may present the symptoms of dengue fever or dengue hemorrhagic fever (DHF), the result of which is often fatal, especially in infants. One recent estimate indicates 390 million dengue infections per year. 3.9 billion people in 128 countries, are at risk of infection with dengue viruses.

Causes of Infection

Disease Agent

Dengue viruses

<Microscopic view of dengue virus> Frederick Murphy
CDC

Vector

Mosquitoes (mostly Aedes aegypti or Aedes albopictus)

<Mosquito (photo: Aedes aegypti)> James Gathany
CDC

Dengue is not directly transmitted from one person to another. That is caused by dengue viruses, which are transmitted by the bite of infected mosquitoes (mostly Aedes aegypti or Aedes albopictus). The symptoms of dengue fever are almost identical across the four types of dengue viruses (DENV 1 through DENV 4).

Symptoms

Symptoms are usually mild, especially for infants, when people are first infected. Individuals then usually develop either the symptoms of dengue fever or of dengue hemorrhagic fever (DHF), or alternatively, may present no symptoms at all.

Dengue fever symptoms

High fevers, severe headaches, pressure-like pain behind the eyes, severe joint, muscle and/or bone pain, skin rashes, mild bleeding (nose and/or bleeds, dot hemorrhage or easy bruising) and leucopenia are typical dengue fever symptoms. If the following symptoms are observed three to seven days after a high fever that lasts from two to seven days in an individual, there is a high probability that the individual concerned has contracted DHF and thus requires immediate treatment. DHF can be fatal if left untreated.

 
Dengue hemorrhagic fever (DHF) symptoms

Symptoms are severe abdominal pains, persistent vomiting, small spots of blood on the skin or large patches of blood under the skin, nose and/or bleeding gums, hematemesis, tarry feces, drowsiness and restlessness, pale complexion or cold, sweaty skin, and difficulty breathing.

 

Treatment

Dengue fever does not become severe if treated immediately after the appearance of initial symptoms. No specific medication currently exists, however, for dengue infection. Due to the increased risk of bleeding, people should avoid analgesics (pain relievers) that contain aspirin. Instead, acetaminophen-based analgesics are recommended. Patients should also drink lots of fluids and have plenty of rest. People should immediately see a doctor if they feel worse (e.g., vomiting and/or severe abdominal pains) in the first 24 hours after the fever subsides.
As with dengue fever, there is no specific medication currently available for DHF. If an early diagnosis is made, however, the disease can be effectively treated with fluid replacement.

Prevention

There is no preventive vaccine for dengue fever. Preventive measures include eliminating those locations where mosquitoes tend to lay their eggs and avoiding and preventing the risk of mosquito bites.
As mosquitoes tend to lay eggs in artificial water containers (including vases and drinking bowls for pets), it is necessary to change the water in suspect areas at least once a week. Mosquito nets sprayed with an insecticide or woven with threads that have been mixed with an insecticide can also effectively prevent mosquito bites.

Regions at High Risk of Infection

According to data from the CDC released in 2013, the risk of contracting dengue fever is high in the tropical and subtropical regions, which is home to more than one-third of the world’s people. Dengue fever is epidemic in Latin America (including Puerto Rico) and Southeast Asia, with seasonal epidemics in Samoa and Guam.

Estimated Number of Infected People

It is estimated the dengue virus infects 390 million people each year, of which 96 million manifest clinically (with any level of severity). The number of cases reported increased from 2.2 million in 2010 to 3.2 million in 2015.

Estimated Number of Deaths from Dengue Fever

An estimated 500,000 people with severe dengue fever require hospitalization each year, a large proportion of whom are children. About 2.5% of those affected die.

Initiatives by Pharmaceutical Companies and NGOs

Dengue fever has been a global concern since the 1950s. As of 2013, there was no preventive vaccine or effective cure for dengue fever. However, many pharmaceutical companies and NGOs have formed partnerships to develop vaccines and drugs to combat the disease and it is hoped that this will result in the development and availability of treatments that can soon be adopted in at-risk regions and elsewhere.
WHO (World Health Organization) has been working on various approaches, including providing support in countries where the disease is epidemic, preparing and disseminating prevention and control guidelines, and developing insecticides and associated technologies.

References
WHO- Neglected Tropical Diseases, accessed March 19, 2014,
http://www.who.int/neglected_diseases/mediacentre/factsheet/en/
CDC- Neglected Tropical Diseases, accessed March 19, 2014,
http://www.cdc.gov/globalhealth/ntd/diseases/