Flu, Viral fever, Swine flu & Dengue

Influenza (also called ‘Flu’) is a Viral infection in which mild to severe symptoms like high Fever, sore throat, muscular pain, headache, acute cough & fatigue etc are seen in patient. The Influenza is caused mainly by three agents, known as Influenza viruses-A, B & C.  A virus, influenza A(H1N1) and A(H3N2) subtypes are currently circulating among humans.

The above symptoms starts 2 days after exposure to the virus and last within less than a week. However, the cough may last for more than two weeks. Children may feel Nausea and Vomiting apart from the above symptoms but, these are not commonly found in adults.

This viral infection spreads easily from person to person and viruses can affect anybody in any age group. The viruses spreads maximum during winter when there is less humidity in atmosphere. The following are the other reasons for spreading of Influenza viruses:

Generally, it is seen that during winters, people mostly remain indoor, hence, they are in close contact with each other for more time and which promotes transmission of viruses.

When the ultra-violet radiation is reduced in winters, the damaging or, killing time of virus is also prolonged, hence, increasing the probability of infection for long duration. Further, the mucous membrane (dehydrated due to drier air) during winters prevents the body to defend effectively against viral infections associated with respiratory system.

The immune system is weakened due to less production of  Vitamin D from Ultra-violet rays  specially during change of season. The Influenza vaccination is very effective way to prevent its infection. Most of the times, the  Influenza viruses develop resistance to certain drugs.

Swine influenza (also called Pig flu / Swine flu or, Hog flu) is an infection caused by any one of several types of Swine Influenza Viruses (SIV). The SIV strains are known as H1N1,  H1N2, H2N1,  H2N3,  H3N1, H3N2.

Many people, being in regular exposure to pigs, have shown higher risk of Swine flu infection.

The symptoms of Swine flu includes Fever, Sneezing, Coughing, difficult breathing problems, early fatigue / tiredness and reduced appetite. The mortality rate is as low as 1 to 4%.

Dengue is a Mosquito (Aedes aegypti)  borne  tropical disease, caused by Dengue virus. The symptoms of  Dengue begin within 4-7 days after the Mosquito’s bite and are visible within 14 days.

The main difference between Dengue and viral fever is that in Viral fever, the patient may have high Fever with running nose, throat pain, mild body ache, weakness while, in Dengue, the patient may have high fever (may rise upto 105°F) with severe body ache, Muscular & Joint pains, nausea and vomiting, Retro-orbital (behind the eye) pain and rashes (pinkish in colour) all over the body within 24 to 48 hours of the fever.


Such patient are advised to undergo Complete Blood Count (CBC) test along with dengue NS1 antigen test. The Dengue is confirmed if NS1 Antigen test is positive (+). However, even if the result is negative (-), the possibility of  Dengue cannot be ruled out and then, the patient needs follow up after 5-7 days with repeated test of  IgG & IgM.

Although, Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS) are uncommon but, they are more severe than regular Dengue. DHF/DSS in beginning shows the  similar symptoms as that of regular dengue fever but, then, the patient reaches to the stage where blood vessels become permeable, causing a breakdown of the circulatory system, fluid loss, and possibly death.

When a mosquito (Aedes aegypti) carrying Dengue virus bites a person, the virus enters the skin through its saliva. It then enters in WBC and reproduces. The WBC move throughout the body and respond by producing a number of signaling proteins, such as cytokines and interferons, which are responsible for many flu like symptoms, like fever severe pains.

The infection is severe if the virus production is largely multiplied and then, many more organs like Bone marrow & Liver be also affected. The fluid from the bloodstream leaks through the wall of small blood vessels into body cavities due to increased permeability of blood capillaries, resulting in less blood supply in blood vessels and further, the blood pressure becomes as low as to supply sufficient blood to vital organs. The Platelet count is severely reduced due to dysfunction of  Bone marrow which is otherwise, necessary for effective blood clotting.

The secondary infection with a different strain of dengue virus whether induces or, not, the risk of Dengue Hemorrhagic Fever(DHF) and Dengue Shock Syndrome (DSS) is not clear. The mechanism of  Antibody Dependent Enhancement (ADE) is widely accepted but, how it works, is not clear.

The infected cells may become necrotic (dead cell) and affect both coagulation and oppose  blood clotting (fibrinolysis) process. The low Platelet count in the blood also affect on normal blood clotting.

The prevention and control on Mosquito bites, that transmit this disease, is very essential and it is possible by eliminating habitats, social mobilization, addition of insecticides (organophosphate or, pyrethroid), getting rid of open source of water, usage of Mosquito nets and insect repellants.

The main precautions, needed to prevent the occurrence of Dengue, are given below:

To take Paracetamol or, Acetaminophen whenever the temperature rises on SOS basis.

The use of NSAIDs like Ibuprofen and Aspirin in dengue MUST be avoided as it aggravates the risk of bleeding in Dengue fever.

To drink sufficient amount of fluids like warm water, clear soup, fruit juice etc (in a small quantity at a time but, more frequently) so as to loosen the mucus and prevent dehydration.

The Antibiotics are helpless in Viral / Dengue fever.

To lower the temperature, sponge body with lukewarm water several times a day.

To seek doctor’s advice well in time.

When the disease proceeds to a critical phase, the leakage of plasma from the blood vessels may occur for 1-2 days and cause the accumulation of fluid in the Abdominal cavity, Chest etc and the lacking of plasma may adversely affect on blood supply to vital organs including Gastrointestinal Tract (GI). The organ dysfunction and severe bleeding occur in less than 5% of all cases of dengue.

The recovery phase starts when leaked fluid is reabsorbed in blood stream and during this process, itching and slow heart rate is noticed. If  the Brain is also affected, it may cause low level of consciousness or, seizures. Dengue fever, developed in a pregnant woman, may be a strong reason of miscarriage or, low weight or, premature baby.

There are five strains of the DENgue Fever Virus (DENV) or, RNA Virus, called serotypes out of which the first four are referred to as DENV-1, DENV-2, DENV-3 and DENV-4 and the 5th type was announced in 2013. The distinctions between these serotypes are based on their Antigenicity.

There is no specific antiviral drug, available in market for dengue. However, maintaining proper fluid balance is important.  The intravenous hydration may be required for 1-2 days only.

The blood transfusion should be initiated at early stage in patients, having low level of Hematocrit (it is the % age of the volume of  whole blood, made up of red blood cells). This measurement depends on the number and size of RBC.

The administration of  intravenous fluids is stopped during the recovery phase to prevent fluid overload condition.  When the patient is out of critical stage, a diuretic like furosemide may be given to eliminate the excess fluid from body.

15th June is observed as International Anti-Dengue Day every year and its aims are to improve  public awareness about dengue and mobilize the resources for its prevention and control.