Dengue

Dengue, transmission, symptoms, phases, pathogenesis, diagnosis, treatment, control

1. Dengue Saajida Sultaana Mahusook

2. Dengue is fast emerging pandemic-prone viral disease in many parts of the world. Dengue flourishes in urban poor areas, suburbs and the countryside but also affects more affluent neighbourhoods in tropical and subtropical countries . The dengue virus (DEN) comprises four distinct serotypes (DEN-1, DEN-2, DEN-3 and DEN-4) which belong to the genus Flavivirus , family Flaviviridae . Severe dengue previously known as dengue haemorrhagic fever Also called as “Break bone fever”

3. Transmission The life cycle of dengue fever virus involves mosquito as a transmitter (or vector) and humans as the main victim and source of infection . Caused by Aedes aegypti Incubation: 3-14 days Affects only humans

4. Pathogenesis Dengue may be caused by any of the dengue viral serotypes. During the feeding of mosquitoes, DENV is injected into the bloodstream, with spillover in the epidermis and dermis, resulting in infection of immature Langerhans cells (epidermal dendritic cells) and keratinocytes. Infected cells then migrate from site of infection to lymph nodes, replicates within cells of the mononuclear phagocyte lineage (macrophages, monocytes, and B cells). The virus is disseminated through the lymphatic system. As a result of this primary viremia , infection of mast cells, dendritic cells, and endothelial cells occurs. The incubation period of dengue infections is 7–10 days. A viraemic phase follows where the patient becomes febrile and infective. Thereafter, the patient may either recover or progress to the leakage phase, leading to DHF and/or dengue shock syndrome. Peak plasma viraemia correlates with the severity of dengue infections. Differences in antibody, cytokine, and T-cell responses are seen among patients with uncomplicated dengue fever or DHF/dengue shock syndrome. For clarity of description, these will be described separately under the headings antibody responses, cytokine responses, and cellular responses to the dengue virus. Generally, infection with one serotype confers future protective immunity against that particular serotype but not against other serotypes. Furthermore, when infected for a second time with a different serotype, a more severe infection may occur. This is due to a phenomenon referred to as antibody dependent enhancement, where antibodies against the first serotype enhance infection with the second serotype.

5. SYMPTOMS FEBRILE PHASE Symptoms last for 2-7 days High grade fever Severe headache, Retrobulbar pain (pain behind eyes) Facial flushing (reddening of skin) Fatigue , nausea Skin erythema, skin rash arthralgia (Pain in back, limbs and joints) Lymphadenopathy CRITICAL PHASE Defervescence Between 3-8 days, Progressive leukopenia ( low level of WBC) “ Dengue hemorrhagic fever/ Dengue shock syndrome” Bleeding from nose, gums Severe case: Enlargement of liver Failure of circulatory system Blood vomit, Blood stool

6. Diagnosis Based on Symptoms Blood test to check for the virus or antibodies • Detection of Non structural protein antigen (NSI ) • Detection of IgM antibodies • IgM ELISA Vector control Avoid travelling to tropical areas/ sub tropical areas in times of outbreak control

7. Treatment No specific medicine • Use pain relievers with acetaminophen and avoid medicines with aspirin, which could worsen bleeding. • Take rest, drink plenty of fluids • In 2019, the FDA approved a vaccine called Dengvaxia to help prevent the disease from occurring in adolescents aged 9 to 16 who have already been infected by dengue.

8. REFERENCE https://www.who.int/denguecontrol/disease/en / https:// www.webmd.com/a-to-z-guides/dengue-fever-reference https:// www.cdc.gov/dengue/symptoms/index.html https :// www.google.com/search?q=dengue+virus&rlz=1C1CHBF_enIN811IN811&sxsrf=ACYBGNQR005xNFHb4feLL-IF4VCb96U86Q:1580832016611&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjkzLKWorjnAhUJy4UKHUOPDyEQ_AUoAXoECBMQAw&biw=1536&bih=755