Climate and Disease – Part I
The Advance of Dengue in the world
Dengue is a tropical, vector spread disease which has become endemic in all hemispheres of the world. The two primary vectors, Aedes aegypti, and Aedes albopictus are present in much of the US and are spreading due to climactic and human factors.
Ae. Aegypti was probably brought to the new world from its African origin by the slave trade. The ships involved in the trade brought the mosquito back to Europe in the early 1800s and it slowly spread throughout the Mediterranean region. Trade routes through the Suez Canal aided the dissemination of this pest throughout Asia and the Pacific regions thereafter. This mosquito is also the primary vector for Yellow Fever, whose origins and dissemination are like Dengue.
Ae. Albopictus was first encountered in Texas in the late 1980s and has since spread more than 20 states in the southeastern USA. Also known as the Asian tiger mosquito, its origin is in the Asia-pacific region. It is thought to have been brought to the US by the importation of used tires.
Due to the current warming process occurring on the earth the range of both mosquitos is expanding. More and more of the US continental territory is under attack by these disease vectors.
The Transmission of Dengue
Dengue is not human to human transmittable. It is also not ‘caught’ by a healthy mosquito in the wild. Dengue is transmitted to a human by the bite of an infected mosquito. If that human is then bitten by another, ‘healthy’, mosquito, that mosquito can go on to infect other humans.
Types of Dengue
There are four known types of Dengue. They are all similar, but different enough so that humans can be infected by all four during their lifetime. In rare cases what is called Severe or Hemorrhagic Dengue can develop which in extreme cases can lead to death.
How to Avoid being Infected by Dengue
Simple: do not get bitten by an infected mosquito. There is no preventive treatment for Dengue. There is a vaccine, not generally available in the US, which is only recommended for those that have already had the disease, since it seems to increase the incidence of Severe Dengue in those that have not had the disease.
Treatment for Dengue
As with other viral diseases, Dengue has no specific therapeutic treatment. The most common symptoms, fever, and pain (Dengue is also known as ‘breakbone fever’) can be treated with Paracetamol (acetaminophen) but not aspirin or Ibuprofen.
Eradication of Dengue
The mosquitos that spread Dengue also spread the yellow fever, chikungunya and Zika viruses. During the construction of the Panama Canal a trio of doctors, William Crawford Gorgas, Joseph Augustin LePrince and Samuel T. Darling implemented a program of mosquito control that greatly reduced the incidence of yellow fever and another mosquito borne illness, malaria. To this day mosquito control is the only cost-effective method of disease reduction.