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PostPosted: 14 Oct 2019 10:42 
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Joined: 19 Dec 2017 14:21
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OVERVIEW
Dengue or dengue fever is a viral illness often encountered in tropical and subtropical regions of the world. Usually, its presentation is similar to a flu-like illness that resolves within a week but it can rarely be very serious, even fatal.

Dengue is a mosquito-borne viral disease and the Aedes mosquito is the vector for the virus. There are currently at least five different 'strains' of the dengue virus, although only the first four appear to infect humans. The virus belongs to the same family as yellow fever, and as chikungunya virus (which can be similar to dengue)

RISK FACTORS
• Living or traveling in tropical areas and subtropical regions increases risk of being exposed to the virus. High-risk areas include Southeast Asia, Latin America , the Western Pacific Islands and the Caribbean.
• Prior infection with a dengue fever virus increases risk of having severe symptoms in case of re-infection.
• A person who has recovered from dengue fever will have immunity to the type of virus that infected but not to the other three types of dengue virus. The risk of developing severe dengue fever, also termed dengue hemorrhagic fever, rises during a second, third or fourth time re-infection

TRANSMISSION OF DENGUE INFECTION
Dengue is transmitted through bite of an infected Aedes aegypti mosquito. It does not spread from one person to another. You can't catch dengue from another person.

This mosquito prefers to be in areas that are densely populated. It lay its eggs in man-made water containers that are not closed and left open. The Aedes mosquito usually bites during the early morning or late afternoon, so night-time mosquito nets may not protect from infection. Only the female Aedes mosquito feeds on blood.

CLINICAL FEATURES OF DENGUE FEVER
Many people, particularly children and teens, may not exhibit any signs or symptoms during a mild infection. Symptoms usually occur four to seven days after being bitten by an infected mosquito.

The non-severe dengue fever causes a high fever touching 104 F degrees, and at least two of the following symptoms
• Headache
• Muscle, bone and joint pain
• Rash
• Retro-orbital pain
• Nausea
• Vomiting
• Swollen glands

Most people recover within about a week, but rarely, symptoms may worsen and can become serious and potentially life threatening. The infection damages blood vessels causing them to become leaky. Additionally, the platelet counts can become severely reduced increasing risk of bleeding. This may result in a severe form of dengue fever, called dengue hemorrhagic fever or dengue shock syndrome.

WARNING SIGNS OF SEVERE DENGUE/ DENGUE HEMORRHAGIC FEVER
Clinical features of dengue hemorrhagic fever or severe dengue, a potentially life-threatening condition
include
• Severe abdominal pain
• Gum or nose bleeding
• Blood in urine, stools or vomit
• Bleeding under the skin, that appear like bruises
• Persistent vomiting
• Difficult or rapid breathing
• Cold or clammy skin (shock)
• Fatigue and tiredness
• Irritability or restlessness

COMPLICATIONS OF DENGUE FEVER
• Damage the lungs, liver or heart.
• Severe drop in blood pressure leading to shock
• Decreased urine output
• Rarely death

DIAGNOSIS OF DENGUE FEVER
Diagnosing dengue fever can be a challenge, because its signs and symptoms can be easily mistaken for other illnesses such as typhoid, malaria or even leptospirosis.

The doctor will usually ask about travel history to dengue endemic areas or mosquito bites. Diagnosis may be confirmed by blood tests although the results may not be available early enough to influence treatment decisions.

BLOOD TESTS
• Full blood count may reveal leucopenia and thrombocytopenia
• Hematocrit- Due to vascular leakage, there will be hemoconcentration and hematocrit will be elevated sometimes to over 20% of baseline values

Detection of virus
a) NS-1 antigen test to detect virus in the first week of fever
b) Detection of viral nucleic acid by RT-PCR
c) ELISA (Enzyme Linked Immunosorbent Assay) - ELISA test will detect IgM antibody to the virus signifying current infection.

TREATMENT OF DENGUE
Non-Severe Type
There is no specific treatment for dengue. If symptoms are mild then symptomatic treatment with paracetamol is useful to reduce fever, headache and aching muscles typical of dengue fever. Avoid preparations containing aspirin.

SEVERE DENGUE
Patients with severe dengue may rapidly deteriorate, and close monitoring is needed. Treatment consists of
• Control of fever with paracetamol, fans and tepid sponging.
• Intravenous fluids and electrolytes to correct hypovolemia and imbalance caused by fluid leak from veins and arteries into the surrounding tissues. Regular checking of blood pressure and hematocrit needs to be done
• Estimation of platelet count and if less than 20,000, platelet support may be required
• Admission to intensive to support vital organs whilst the disease runs its course.
• Treatment for secondary bacterial infections, which often occurs in dengue

PREVENTION OF DENGUE
Dengue Vaccine
Dengvaxia is a live attenuated tetravalent vaccine made by recombinant DNA technology. Evidence indicates that CYT-TDV is partially effective in preventing infection, but has a risk of more severe disease in those who have not been previously infected and later contract the infection. It is not clear why the vaccinated seronegative persons have more severe disease, but a. probable theory is the due to phenomenon of antibody-dependent enhancement.[

Other Measures
1. Avoid breeding of mosquitoes by removing water from air coolers and other containers regularly. Keep containers containing water closed so that mosquitoes cannot lay eggs
2. Wear clothes to that cover arms and legs to prevent mosquito bites and treat them with repellents like permethrin
3. Use mosquito repellents containing N,N-diethyl-3-methylbenzamide (DEET) regularly and mosquito nets during night although dengue mosquito typically bites during the day
4. Apply mosquito screens to front doors and windows to prevent mosquito entry into house
5. Chemical mosquito larvicide such as Temephos can be used in drinking water
6. Regular spraying of pesticide or fogging
7. Avoid travel to dengue endemic areas such as parts of Africa, Asia, Caribbean and Pacific if possible
8. Avoid heavy perfumes and scents as these may attract mosquitoes

KEY POINTS
• Dengue is a mosquito borne viral infection
• Caused by bite of female Aedes aegypti mosquito
• Illness can be mild to severe (dengue hemorrhagic fever)
• Complications include thrombocytopenia and hypovolemia
• Diagnosed by detection of viral antigen or IgM antibody in patient's serum
• There is no cure for dengue, only symptomatic treatment
• Dengvaxia is the only available vaccine to prevent infection but has certain limitations
• Prevention is mainly by measures to prevent breeding of mosquitoes and mosquito bites


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 Post subject: DENGUE FEVER
PostPosted: 03 Nov 2019 22:27 
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Joined: 26 Feb 2013 10:59
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India is home to nearly a third of the global population at risk of dengue. The virus that causes dengue disease is divided into four closely related serotypes (dengue virus 1, 2, 3 and 4), and those serotypes can be further divided into genetic variants, or subtypes. I am told that Telangana has witnessed the maximum number of dengue cases this year. It reported nearly 3,000 cases in the month of September. Although the State government says there were no deaths, unofficial reports indicate 56 people died.

In the USA, USFDA along with Centres for Disease Control and Prevention (CDC) has this year approved the first vaccine for the prevention of dengue disease caused by virus serotypes (1,2,3, and 4). “Dengvaxia, was the first vaccine approved for the prevention of dengue disease caused by all dengue virus serotypes (1, 2, 3 and 4).” Although the report said that the news will help India fight the disease, experts working in the field indicate that India will have to wait for a decade for the new drug to arrive in India! I am not sure why.

Infection with a particular kind of dengue virus builds lifelong immunity to it, but the person is still vulnerable to infection with the other types of dengue viruses. Infection with other types in a person who already had a dengue fever in the past is called secondary dengue and has been found to be severe. This is supposed to be due to more severe immunological response in the body

You mentioned about the risk of vaccinating patients who have not been exposed to the infection previously. Dengvaxia, developed by Sanofi, was licensed in 2015. The long-term follow-up of the Sanofi phase III efficacy trial participants did reveal potential safety concerns.

The possibility of risk for seronegative people was raised by WHO and published in July 2016. Following a consultation of the Global Advisory Committee on Vaccine Safety, they report that the dengue vaccine CYD-TDV, sold under the brand name Dengvaxia, prevents disease in the majority of vaccine recipients but it should not be administered to people who have not previously been infected with dengue virus.The paper indicated that the vaccination may be ineffective or may theoretically even increase the future risk of severe dengue illness in those who are seronegative at the time of first vaccination regardless of age. As this risk had at that time not been seen in the age groups for which the vaccine was licensed, WHO issued a conditional recommendation, emphasizing the use of the vaccine in populations having been previously infected with dengue virus.


For vaccine recipients who present with clinical symptoms compatible with dengue virus infection, access to medical care should be expedited to allow for proper evaluation, identification, and management of severe forms of the disease.

A safe and efficacious dengue vaccine continues to be sought globally. India has joined these efforts in recent years, and is poised to initiate the clinical development of two types in the near future. Sathyamangalam Swaminathan and Navin Khannaa writing in International Journal of Infectious Diseases mention that Indian companies have licensed a live attenuated experimental vaccine from the USA and they are also developing an indigenous tetravalent dengue subunit vaccine, DSV4.

Remember: Even if you have had Dengue in the past you are not immune to further infection. Dengvaxia, prevents disease in the majority of people who receive the vaccine but it should not be administered to people who have not previously been infected with dengue virus.


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