MDB Series - Dengue Part 4

This post is fourth in the series about mosquito borne diseases.

Disclaimer: This post is for information purposes only. This is not written by any medical doctor or government official or anyone related to the worldwide research on mosquito borne diseases. Neither is this a complete information about dengue and should not be relied on for reference. However, we have taken care to refer to reliable sources on the web, the links to which would be provided at the end of the post.

Diagnosis

Clinical diagnosis is usually based on reported symptoms and physical examination. Since dengue has symptoms similar to many viral infections, diagnosis is made when there is fever combined with any two of the following conditions – nauseas and/or vomiting, body pain, rash, low white blood cell count and positive tourniquet test. The tourniquet test is useful in situations where laboratory conditions are not available.

The warning signs occur before the onset of severe dengue. To further determine if it is dengue, the patient’s blood is tested for the presence of the virus and antibodies. Serum samples from the patients’ body are collected for more accurate tests.

ELISA (Enzyme-linked Immuno Sorbent Assay) is a test conducted to find specific anti-dengue antibodies. This is the test conducted by the Government Hospitals in Tamilnadu for diagnosis.

There is a more expensive, complicated but more accurate test called PCR (Polymerase Chain Reaction) which is done to identify genome sequence of the virus from the serum sample or CSF (cerebro spinal fluid) of the patient. This method was introduced in 2012.

However, these tests are useful in diagnosis only when the condition is severe.

Sources: Dengue Virus Net, WHO, WebMD, Wikipedia, Medindia, US National Library of Medicine, Ministry of Health and Family Welfare(India)

MDB Series - Dengue Part 3

This post is third in the series about mosquito borne diseases.

Disclaimer: This post is for information purposes only. This is not written by any medical doctor or government official or anyone related to the worldwide research on mosquito borne diseases. Neither is this a complete information about dengue and should not be relied on for reference. However, we have taken care to refer to reliable sources on the web, the links to which would be provided at the end of the post.

Development

When an infected mosquito bites a human being, the dengue virus enters the blood stream via the mosquito’s saliva. The virus first binds to dendritic cells that have the ability to identify pathogens.  They replicate inside the cells and use cell proteins to multiply. They enter the white blood cells and continue to replicate as the cells move throughout the body through blood. Through the walls of small blood cells, fluid leaks into other body cavities, leading to less blood circulation. This leads to low blood pressure and as consequence there is no sufficient blood flow to vital organs.

When initially the virus attacks a cell, the white blood cells produce a protein called interferon, which cause the fever like symptom. As the blood flow decreases, it leads to dysfunction of bone marrow which further leads to low platelet count. Platelets are necessary to clot blood and arrest flow of bleeding. This is the cause of a severe form of dengue called dengue haemorrhagic fever.

Symptoms

Usually most dengue infected people don’t exhibit many symptoms. Sometimes there are mild generic symptoms like fever. Very few people have severe fever. The incubation period for this disease ranges from 3 to 14 days, but usually it is 4 to 7 days.

The following are the typical symptoms of dengue,

·         Fever

·         Rash and/or increased skin sensitivity

·         Fatigue

·         Headache

·         Nausea

·         Vomiting

·         Cough

·         Sore throat

·         Joint ache

·         Muscle inflammation

·         Nasal stuffiness

·         Swollen lymph nodes

·         Pain behind the eyes

·         Mild bleeding

Dengue per se is not fatal. However, when a high fever is accompanied by any of the above listed symptoms, dengue should be suspected as variations of this disease are fatal.

Variations

There are more severe versions of this disease. Dengue haemorrhagic fever causes bleeding and low levels of blood platelets, resulting in death most often.  Dengue shock syndrome is caused when the blood pressure drops to dangerously low levels. When a patient is infected a second time by dengue, they will have complications associated with the disease. 

Sources: Dengue Virus Net, WHO, WebMD, Wikipedia, Medindia, US National Library of Medicine, Ministry of Health and Family Welfare( Govt of India)

MBD Series - Dengue Part 1

We are posting a series about Mosquito-Borne Diseases, along with our other regular articles. This is the first post in that series.

Disclaimer: This post is for information purposes only. This is not written by any medical doctor or government official or anyone related to the worldwide research on mosquito borne diseases. Neither is this a complete information about dengue and should not be relied on for reference. However, we have taken care to refer to reliable sources on the web, the links to which would be provided at the end of the post.

Let's start with,

Dengue

Dengue is a Spanish word, pronounced 'den-gee'. Though its origins are not clear, it's believed to have been from the Swahili phrase ka dinga pepo, that claims the disease to have been caused by evil eye. It has also been called: dandy fever, breakbone fever, break fever etc.

Dengue is the second disease to be identified as caused by virus. The first was the yellow fever.

It is found in the tropical and subtropical regions, especially, 

• the Indian Subcontinent
• some parts of the Caribbean
• some parts of the Central and South Americas
• sub-Saharan Africa
• south east Asia
• the Pacific islands

Dengue has also been identified in other parts of the world where it spread through travellers.

It is spread through mosquitoes of the Aedes genus, Aedes aegypti most known among them. The mosquitoes of this genus are known to bite during the day, dawn and dusk. Dengue is spread via human to human transmission by the females of aedes.

History

The earliest available record of a case that could have been dengue fever was found in the Chinese medical encyclopaedia from the Jin dynasty (265 to 420AD) which referred to a 'water poison' associated with flying insects.

Later, around 15th to 19th centuries AD, Aedes aegypti (the primary vector) spread to other places from Africa due to globalisation and Slave Trade. There have been descriptions about an epidemic in the 17th century.

The most plausible records of dengue epidemics available, however, from 1779 and 1780, when an epidemic swept across Asia, Africa and North America.

In a 1789 report that the US founding father Benjamin Rush, a physician, wrote on the 1780 epidemic of Philadelphia, he used first the term Breakbone fever. Rush however used the more formal Bilious Remitting Fever as the title of his report.

Confirmation of the transmission of dengue by the aedes mosquitoes came in 1906; and in 1907, dengue was the second ever disease know to be caused by a virus. Though much research has been going on for centuries, the basic understanding about dengue was completed in early 20th century.

Since the 17th century epidemic, dengue epidemics have been quite few till the Second World War. The spread of dengue since World War II is attributed to ecological disruptions. The same reason is given for the spread of different serotypes of dengue to new areas, and also for the emergence of dengue haemorrhagic fever- a more severe and probably fatal variation of the dengue fever.

Sources: Dengue Virus Net, WHO, WebMD, Wikipedia, Medindia, US National Library of Medicine, Ministry of Health and Family Welfare (Govt of India)