Dengue Fever- Symptoms, diagnosis, treatment and prevention.

Dengue fever also known as breakbone fever or Dandy fever is a viral disease occurring in tropical and subtropical areas.It is caused by dengue virus, which belongs to family Flaviviridae and is transmitted by mosquito bite. It is an endemic disease in tropical countries like India with peaks seen during rainy season.

 

There are 4 known serotypes of the virus named as DENV1, DENV2, DENV3 and DENV4. Infection by one serotype does not confer immunity to another type.

Aedes aegypti

 Symptoms of Dengue fever

Common symptoms include high grade fever, headache, rash (appearing between 2nd and fifth day of fever), weakness, vomiting, muscle and joint pain. Approximately 1 in 20 patients progress into severe forms of the disease namely Dengue hemorrhagic fever and dengue shock syndrome which can be life threatening.

When to suspect??

Fever with any  of the aforementioned symptoms of dengue fever.

If any history of travel to tropical area or  high risk areas.

When to suspect severe dengue??

Warning symptoms for severe dengue include severe abdominal pain, persistent vomiting, bleeding from nose or gums, difficulty breathing and lethargy.

Investigations required

Blood samples are collected from the patient for

Serological tests

1) MAC-ELISA to detect IgM antibody against dengue virus - useful after 4 days of onset of fever

2) ELISA for NS1 antigen (non structural protein 1 of the virus) - used within 4 days of onset of fever.

RT-PCR

Confirms dengue infection by detecting the viral genomic sequences.

To be performed within 7 days of onset of symptoms.

Other investigations

Complete blood count:

Total white blood cells count are on the lower side.

Patients has very low platelet counts( normal 1.5 to 4 lakh/cubic mm) and may reach as low as less than 40000 during day 3-7 of fever. Platelet count can be low in other viral infections also. It is the trend of platelet count that is important than a single value. But,when platelet count drops below 20000, there are more chances of developing bleeding complication as seen in dengue hemorrhagic fever.

Hematocrit: the ratio of volume of red blood cells to total volume of blood. Hematocrit increases due to plasma leakage from blood vessels.

Treatment and outcome

Avoid self medications and  seek  medical attention.

Mild cases can be managed at home by maintaining adequate hydration and rest. In children, watch for signs of dehydration like decreased frequency of urination, sunken eyes, dry lips and decreased activity.

Fever can be managed using antipyretics like paracetamol (avoid aspirin and ibuprofen ) and tepid sponging. 

Look for warning symptoms, as severe cases require  hospitalization or sometimes  ICU admission for close monitoring of vitals.

There are no specific drugs against dengue virus.

Patients with severe dengue might require Intravenous fluid administration with constant blood pressure monitoring and blood investigations.

Less often platelet transfusion might be required in patients with severe hemorrhagic manifestations and very low platelet count.

 Typically, Dengue fever is a self limiting disease with a mortality rate less than 1% with proper medical care. But if left untreated the death rate  of severe dengue can go as high as 20%.

 

Prevention

Dengue fever is not contagious, direct human to human transmission does not happen. It is transmitted through the bite of Aedes aegypti also known as tiger mosquito because of its striated appearance. These mosquitoes are most active during day light and all precautions need to be taken to reduce exposure.

 

To prevent breeding of Aedes aegypti mosquitoes

• Remove the breeding sites

• Drain out stagnant water from sites from balcony, terrace and garden areas. Common sites include empty pots, water coolers, Tyre,coconut shells.

• Observe dry day once a week.

• Keep drains functional and remove any blocks to avoid stagnant water.

• Guppy fishes which feed on mosquito larvae can be used as a biological control in ponds.

• During outbreaks, mosquito breeding can be controlled by fogging

 

To prevent mosquito bites

• Use mosquito repellants 

• Wear protective clothing to ensure arms and legs are not exposed before going out.

• Install door and window screens 

• Use mosquito nets during sleeping

Dengue vaccine

Dengvaxia is an FDA approved dengue vaccine which is available in some countries for people of  9-45 years of age with confirmed prior dengue virus infection.This is  because the people who receive the vaccine and have not been previously infected with a dengue virus may be at risk of developing severe dengue if they get dengue after being vaccinated.

Dengue viruses and the virus that causes COVID19 can cause similar symptoms during early stages. To read more about COVID19 symptoms,laboratory diagnosis and prevention.

Dengue fever is usually a self limiting disease and improves on symptomatic management along with adequate rest and hydration. Precautions needs to be taken at all levels as prevention is always better than cure.