Seeing that it is currently spreading in Belize we thought it would be a good topic to post today. Educating yourself on this disease will prove to be beneficial to you and the people around you. We tend to depend on the health departments to figure out ways ensure we are safe from these diseases, however it should fall on us to ensure that our neighborhoods are safe and clean and that we do not provide places for mosquitoes to breed. Like everything else we must take this matter seriously and make the first step to prevent it from spreading.
Dengue (DF) and dengue hemorrhagic fever (DHF) are caused by one of four closely related, but antigenically distinct, virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), of the genus Flavivirus. Infection with one of these serotypes provides immunity to only that serotype for life, so persons living in a dengue-endemic area can have more than one dengue infection during their lifetime. DF and DHF are primarily diseases of tropical and sub tropical areas, and the four different dengue serotypes are maintained in a cycle that involves humans and the Aedes mosquito. However, Aedes aegypti, a domestic, day-biting mosquito that prefers to feed on humans, is the most common Aedes species. Infections produce a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease. Important risk factors for DHF include the strain of the infecting virus, as well as the age, and especially the prior dengue infection history of the patient.
The first reported epidemics of DF occurred in 1779-1780 in Asia, Africa, and North America. The near simultaneous occurrence of outbreaks on three continents indicates that these viruses and their mosquito vector have had a worldwide distribution in the tropics for more than 200 years. During most of this time, DF was considered a mild, nonfatal disease of visitors to the tropics. Generally, there were long intervals (10-40 years) between major epidemics, mainly because the introduction of a new serotype in a susceptible population occurred only if viruses and their mosquito vector could survive the slow transport between population centers by sailing vessels.
A pandemic of dengue began in Southeast Asia after World War II and has spread around the globe since then. Epidemics caused by multiple serotypes (hyperendemicity) are more frequent, the geographic distribution of dengue viruses and their mosquito vectors has expanded, and DHF has emerged in the Pacific region and the Americas. In Southeast Asia, epidemic DHF first appeared in the 1950s, but by 1975 it had become a frequent cause of hospitalization and death among children in many countries in that region.
The emergence of dengue/DHF as a major public health problem has been most dramatic in the American region. In an effort to prevent urban yellow fever, which is also transmitted by Ae. aegypti, the Pan American Health Organization started a campaign that eradicated Ae. aegypti from most Central and South American countries in the 1950s and 1960s. As a result, epidemic dengue occurred only sporadically in some Caribbean islands during this period.
The reasons for the dramatic global emergence of DF/DHF as a major public health problem are complex and not well understood. However, several important factors can be identified.
- First, major global demographic changes have occurred, the most important of which have been uncontrolled urbanization and concurrent population growth. These demographic changes have resulted in substandard housing and inadequate water, sewer, and waste management systems, all of which increase Ae. aegypti population densities and facilitate transmission of Ae. aegypti-borne disease.
- In most countries the public health infrastructure has deteriorated. Limited financial and human resources and competing priorities have resulted in a “crisis mentality” with emphasis on implementing so-called emergency control methods in response to epidemics rather than on developing programs to prevent epidemic transmission. This approach has been particularly detrimental to dengue control because, in most countries, surveillance is passive; the system to detect increased transmission normally relies on reports by local physicians who often do not consider dengue in their differential diagnoses. As a result, an epidemic has often reached or passed its peak before it is recognized.
- Increased travel by airplane provides the ideal mechanism for infected human transport of dengue viruses between population centers of the tropics, resulting in a frequent exchange of dengue viruses and other pathogens.
- Lastly, effective mosquito control is virtually nonexistent in most dengue-endemic countries. Considerable emphasis in the past has been placed on ultra-low-volume insecticide space sprays for adult mosquito control, a relatively ineffective approach for controlling Ae. aegypti.
No dengue vaccine is available. Recently, however, attenuated candidate vaccine viruses have been developed. Efficacy trials in human volunteers have yet to be initiated. Research is also being conducted to develop second-generation recombinant vaccine viruses. Therefore, an effective dengue vaccine for public use will not be available for 5 to 10 years.
Signs and symptoms
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. Cases of DHF also show higher fever, variable haemorrhagic phenomena, thrombocytopenia, and haemoconcentration. A small proportion of cases lead to dengue shock syndrome (DSS) which has a high mortality rate. DHF combined with a cirrhotic liver has been suspected in rapid development of hepatocellular carcinoma (HCC). Given that the Dengue virus (DEN) is related to the Hepatitis C virus, this is an avenue for further research as HCC is among the top five cancerous causes of death outside Europe and North America. Normally HCC does not occur in a cirrhotic liver for ten or more years after the cessation of the poisoning agent. DHF patients can develop HCC within one year of cessation of abuse.
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 critical. 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.
Aspirin and non-steroidal anti-inflammatory drugs should be avoided as these drugs may worsen the bleeding tendency associated with some of these infections. Patients may receive paracetamol preparations to deal with these symptoms if dengue is suspected.
Traditional and emerging treatments
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.
In Brazilian traditional medicine, dengue is treated with cat’s claw herb, which is for inflammation and does not prevent dengue.
In Malaysia, dengue is treated by some using natural medicine. Mas Amirtha and Semalu developed by the Alternative Medicine Research Institute, Center for Asia. The treatment is speculated to be able to arrest and reverse the viral infection and prevent the disease from advancing into a critical stage, though no evidence has yet shown effectiveness. In Philippines dengue patients use tawa-tawa herbs and sweet-potato-tops juice to increase the platelets counts and revived the patients.
Primary prevention of dengue mainly resides in mosquito control. There are two primary methods: larval control and adult mosquito control. In urban areas, Aedes mosquitos 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 mosquitos. Larvicide treatment is another effective way to control the vector larvae but the larvicide chosen should be long-lasting and preferably have World Health Organization clearance for use in drinking water. There are some very effective insect growth regulators (IGRs) available which are both safe and long-lasting (e.g. pyriproxyfen). For reducing the adult mosquito load, fogging with insecticide is somewhat effective.
Prevention of mosquito bites is another way of preventing disease. This can be achieved by using insect repellent, mosquito traps or mosquito nets.
- Health: How Dengue Spreads (voanews.com)
- Tracking the spread of dengue fever: Domestic networks drive rapid transmission of human infection (eurekalert.org)
- Dengue showing global ‘epidemic potential’: WHO (terradaily.com)
- Eliminate Pesky Mosquitoes From Your Backyard This Summer Using a Mosquito Misting System From The Perfect Light (landscapelightingtx.com)