Viral weapon active against humans.
Safety Precautions for Dengue Fever Casualties
Standard Precautions defined by the 1996 CDC guidelines should be adopted for handling patients.
Droplet precautions may also be necessary.
Mosquito control should be practiced.
Biosafety level 2 practices should be adopted for handling of samples.
|Causative organism: |
(Systematic name in 1997)
|Alternative disease names:||
Click here for a detailed description of Flaviviruses
|Vector Involvement:||Transmitted by culicine mosquitoes of the genus Aedes.|
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The disease is typified by the sudden onset of a severe fever, chills, headache, pain behind the eyes (retro-orbital pain), photophobia, and joint and muscle pain. The victim may appear flushed at the onset of the fever and a rash may appear on the torso after 3-4 days and spread to the rest of the body. Lymph nodes are often inflamed.
Differential DiagnosisOther disease or conditions that need to be eliminated
|Other infectious diseases||Other problems|
Symptoms and effects.
Dengue shows a number of atypical forms without fever or clinically significant symptoms.
The commonest form has an incubation period of 5-8 days followed by the onset of a fever, violent headache, chills, retroorbital pain, with a rash developing after 3-4 days. The fever usually lasts 4-7 days and most people make a complete recovery without complications. Some individuals may take several months to recover. Fatalities are rare.
Complications can arise in areas where the disease is endemic and repeated infection is possible. These are dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). They are most often found in children who have been previously had Dengue fever. DHS appears first with the child developing internal hemorrhages that lead to the onset of DSS. The condition is fatal in 10-20% of cases.
Medical and Physical Countermeasures.
A vaccine is not available.
No specific therapies are available.
The virus is killed by heat and is susceptible to common disinfectants; 70%
ethanol, 1% sodium hypochlorite, 2% glutaraldehyde.
Agent Properties and Potential Uses
The virus is relatively stable and can survive for up to two days in dried body fluids, e.g. blood. It is not easily transmitted between individuals and is normally only transmitted by mosquito bites. The virus can be carried by several members of the widely distributed genus Aedes and by the genus Stegomyia. It takes several days for a mosquito to become a vector after biting an infected individual, but it remains infected for life.
In its native environment, the virus uses other mammals as a reservoir with occasional transmittal to man. In urban areas, it can use man as a reservoir for human to human transmission.
Response to an attack has therefore to include treatment with insecticides and continued monitoring of local mosquito and wild animal populations for the presence of the virus, even after the instant crisis is past.
Terrorist Acquisition and Attempted Use.
The exact origins of the disease are not clear and arguments have been made that it originated in Africa and was spread worldwide with the slave trade. The most convincing explanation for the name dengue is that it is derived from the Swahili "Ka-Dinga pepo" that describes the disease as a sudden cramp like disease caused by an evil spirit. It has also been argued that it originated in the Malay Peninsula of Indochina. Regardless, in the wild the virus has a life cycle very similar to that of yellow fever involving passing between primates living in the jungle canopy and mosquitoes that feed on them. It is believed that the virus was transferred to man by the bite of the tiger-striped mosquito (Aedes albopticus) as man began clearing the jungle and building settlements. The commonest vector is now the closely-related mosquito Aedes aegypti which is African in origin but has spread throughout the tropics in the Old and New Worlds.
The earliest reports of a dengue-like disease are from Chin Dynasty China (265-420 AD). The first rigorously documented outbreaks occurred almost simultaneously in:
The virus was identified in the 1940's when it became a concern to the armies fighting in Pacific and Asia as it was causing a large number of non-combat casualties to Allied and Japanese forces. Japanese scientists first identified the virus in 1943 and were quickly followed by U.S. researchers. By 1956 the four serotypes of the virus were identified and every outbreak of the disease since has been due to a virus belonging to one of the four serotypes.
Work is being done on the development of vaccines against the disease but there are currently none proven safe and effective for human use. The primary method of preventing the spread of the disease is by controlling the mosquito vectors and this has proven effective and the disease appeared to be on the decline for many years, however it had a resurgence in the 1990's and remains a major public health problem in many areas and the current situation has been designated a global pandemic.
The most worrisome aspect of the resurgence is that it has come with an increase in the frequency and severity of dengue hemorrhagic syndrome, a severe complication of the disease normally only arising upon re-infection. Typically, when diseases first crossover to man they are at their most severe (syphilis is the prime example of this) and over the years they become less severe as they adapt themselves to a new host. Dengue appears to be running against the stream, making it a greater public health and weapons threat.
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