Dengue: All we need to know

As dengue fever is turning into a severe health crisis across the country, it is important that you know about the disease, how it spreads, and what you should do to minimize the risk of the disease.

What is Dengue?

Dengue fever is a painful, debilitating mosquito-borne disease. Aedes aegytpi, a species of mosquito, is the carrier of any one of the four closely related dengue virus serotypes -- DEN 1, DEN 2, DEN 3 and DEN 4.

The same species also causes Yellow fever, chikungunya and zika infections

A small percentage of people who had been previously infected by one of the serotypes may develop bleeding and endothelial leak if infected by another serotype which is then referred to as severe dengue or dengue hemorrhagic fever or dengue shock syndrome.

Infection with one serotype induces a lifelong immunity to the specific serotype but partial immunity to the other serotypes.

Symptoms appear between 3 to 14 days (on average 4 to 7 days) after the infective bite.

The natural course of the disease has 3 phases:

Febrile phase

Critical phase 

Convalescent phase or recovery

Epidemiology

The fever is usually self limiting with a mortality of les than 1% if detected early

Dengue affects infants, young children and adults.

Prevalence of dengue is  estimated to be  3.9 billion people, in 128 countries, are at risk of infection with dengue viruses.

 The number of cases reported increased from 2.2 million in 2010 to over 3.34 million in 2016. Although the full global burden of the disease is uncertain, the initiation of activities to record all dengue cases partly explains the sharp increase in the number of cases reported in recent years.

Transmission

Transmitted to humans by bite of Aedes mosquito. The mosquito is usually tropical.

Individual risk factors determine the severity of the disease

These include: secondary infection, age, ethnicity and presence of chronic disease

 

Symptoms of Dengue fever

Dengue fever has an incubation period of 3-14 days and the symptoms usually last 2-7 days.

Many individuals may however be asymptomatic.

The prodrome phase mostly consists of chills, erythematous mottling rash and facial flushing lasting 3 days.

Children less than 15 years may have a none specific febrile illness accompanied y a maculopapular rash

If one presents with the following symptoms the disease should be suspected especially if they had travelled to a highly endemic zone

Criteria for dengue

Probable dengue

Live in/ travel to endemic area

Fever and 2 of the following:

• Nausea, vomiting
• Rash, aches and pain
• Tourniquet test positive
• Leucopenia
• Any warning sighns

Warning signs

• Abdominal pain
• Persistent vomiting
• Clinical fluid accumulation
• Mucosal bleeding
• Lethargy, restlessness
• Liver enlargement> 2cm
• Laboratory increasw in H CT

Severe dengue

• Severe plasma leakage
• Severe bleeding
• Organ involvement(

Cns : impaired consciousness

Liver, kidneys

DIAGNOSIS

Laboratory criteria for diagnosis include

Demonstration of a four fold or greater change in reciprocal of IgG or IgM titre

Presence of dengue antigen in autopsy tissue via immunohistochemistry

Other work up include:

CBC

Serum protein and albumin level

Liver profile

Coagulation profile

Findings include: thrombocytopenia, leucopenia, mild to moderate elevation of aspartate aminotransferenses and alanine transferase

Severe dengue presents with: hypoproteinemia, prolonged protrombin time, increased hematocrit level, decreased fibrinogen

MANAGEMENT

SUPPORTIVE MANAGEMENT

1.Oral rehydration therapy for patients with moderate dehydration

Crystalloids (  ringers lactate, normal  saline,) or volume expanders

Patients with signs of severe dengue may require admission and close monitoring of their volume status

Patients with internal bleeding may require transfusion while those with coagulopathy require fresh frozen plasma

Milk, fruit juice and oral rehydration solution can also be used

1. Analgesics

Acetaminophen for fever relieve

Aspirin and other NSAIDS should be avoided

Use tepid sponging to bring down the fever in between the Paracetamol dosing. Soak a clean towel in moderately warm water, then squeeze the excess water away and wipe the body to reduce fever

1. Bed rest

Patients should gradually resume normal activity during convalescence period

When to get alarmed

• Bleeding:Red spots or patches in the skin, Bleeding from nose or gums,Vomiting blood,Black colored stool,Heavy vaginal bleeding
• Frequent vomiting
• Severe abdominal pains
• Drowsiness, mental confusion or seizures
• Difficulty in breathing

Prevention and control

The main prevention technique is avoiding getting bitten by the vector by measures which include:   

• preventing mosquitoes from accessing egg-laying habitats by environmental management and modification;
• disposing of solid waste properly and removing artificial man-made habitats;
• covering, emptying and cleaning of domestic water storage containers on a weekly basis;
• applying appropriate insecticides to water storage outdoor containers;
• using of personal household protection measures, such as window screens, long-sleeved clothes, repellents, insecticide treated materials, coils and vaporizers (These measures have to be observed during the day both at home and place of work since the mosquito bites during the day);
• improving community participation and mobilization for sustained vector control;
• applying insecticides as space spraying during outbreaks as one of the emergency vector-control measures;
• active monitoring and surveillance of vectors should be carried out to determine effectiveness of control interventions.

Immunization

The first dengue vaccine, Dengvaxia  developed by Sanofi Pasteur was licensed in December 2015 and has now been approved  in 20 countries for use in endemic areas in persons ranging from 9-45 years of age.  It is given in 3 doses 0, 6 and 12 months. WHO issued a conditional recommendation on the use of the vaccine for areas in which dengue is highly endemic as defined by seroprevalence of 70% or higher. Later a retrospective study to determine serostatus at the time of vaccination were released. The analysis showed that the subset of trial participants who were inferred to be seronegative at time of first vaccination had a higher risk of more severe dengue and hospitalizations from dengue compared to unvaccinated participants. 

Writer:Dr. Ishrat Rafique Eshita

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