Dengue fever: Pathogenesis and its clinical features

 Dengue fever: Pathogenesis and its clinical features 



It is also called as break bone fever Dandy fever or hemorrhagic fever.

It is a tropical viral disease transmitted by mosquitoes, in tropical and subtropical countries when the climate is hot and humid the virus is carried by mosquito of Aedes type specially Aedes aegypti.

  • Causative agent

Diseases caused by a flavi virus,  the virus is of five types. one attack usually give immunity for about 9 months many such attack give life time permanent immunity.

○ Incubation period

5 to 6 days (3-14 days) 

○ Pathogenesis

Mosquito bite of aedes aegypti is mostly in daytime. They mostly target the back of neck and ankles of humans. Human serves as primary Reservoir for dengue. Person with Dengue virus in the blood can be transmitted to mosquito during bite. In humans viral replication takes place in target dendritic cells full stop infection of target cells results in production of immune mediators that initiate cellular and humoral response.

○ Clinical features



1. High grade fever fever is usually around 104°F, continuous or saddle back ,Break on fourth or fifth day usually last for 7 to 8 days.

2.  Headache. 

3. Back ache, generalised body pain

4. Arthralgia (muscles and joint pain)

5.  nausea, vomiting

6. Painful red eyes, lacrimation

7. Skin Rash gradually develops on dorsal of hand and feet and spread centripetally

8.  mild haemorrhage may occur (petechiae, bleeding gums, epistaxis, hematuria) 

There is prodromal phase of today's with symptoms of malaise and headache

○ Dengue Hemorrhagic Fever

In some cases the disease develops into life-threatening dengue hemorrhagic fever full stop the hemorrhage is in the form of petechie, ecchymosis, epistaxis, melaena,  bleeding gums hematuria and even circulatory failure. blood platelets fall to very low level.

This is a critical phase. There maybe organ dysfunction  and severe bleeding from gastrointestinal tract. Shock (dengue shock syndrome) may occur in 5% of cases.

There is a recovery phase with severe itching and slow heart rate. Pregnant women suffering with Dengue has a high risk of miscarriage, low birth weight and premature birth.

○ Investigations

1.  CBC- leucopenia

2. Thrombocytopenia- decreased platelet count.

3. SGOT, SGPT is increased

4. Rise in antibody titres-IgG and IgM for dengue specific antibody are produced after 5-7 days.

5. Virus can be recovered from blood.

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